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eForth for cheap STM8S gadgets

Turn cheap stuff from AliExpress into interactive development kits!

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Turn cheap STM8 µC boards into Forth development kits!

The code is based on Dr. C.H. Ting's interactive eForth for the STM8S Discovery, am STC Forth with Kernel, interpreter, and compiler in 5.5K Flash. I squeezed the interactive demo into 3.7K to get the most out of the 8K of an STM8S Value Line µC for $0.20.

Many features were added: Flash programming, Forth interrupt handlers, background task, vectored I/O, drivers for 7S-LED displays, analog and digital I/O, DO..LOOP, CREATE..DOES>... There is a simple framework for configuration, feature selection, support of new boards. and other STM8 µCs. Mixing C with Forth is possible, too, e.g. as a shell for testing, setting parameters, or for scripting.

Some HaD projects now use the STM8EF code. Check out the docs here and GitHub Wiki!

What is it good for?

The project delivers configurable board support code for selected targets, and docs. Besides its modest size, the TG9541/STM8EF code has a long feature list. Using the code for embedded control applications is subject to new projects.

The code on GitHub can be used in many ways:

  • for writing alternative firmware Chinese commodity boards (e.g. thermostats, DCDC converters, or relay boards)
  • for embedded systems with an interactive shell (scriptable and extensible)
  • for creating smart SPI, I2C, or RS232 smart sensors with a scripting shell, e.g. for RaspberryPi, Arduino, or ESP8266
  • as an interactive environment for exploring the STM8 architecture
  • for learning Forth. It's easy and fun - find out why in the text below!
  • ...

Why a Forth for Cheap Chinese boards?

Because it's fun: cheap mass-produced imperfection is a playground for creativity :-)

Right now, the W1209 is my favorite target: it's a rather complete embedded control board with a UI at a very good price. It's as cheap as it looks, and the challenge is in it's imperfections: the guy who designed the board clearly didn't have a connected application in mind, and I had a lot of fun making it do things it was never intended to do.

There are challenges, like the lack of communication ports. The "sensor connector" can either be used for communicating, or for sensing. What if you need sensing and communication at the same time? Maybe the "update connector" can be used as a home brew field bus interface? A lot is possible with the right idea, and the right software!

Which target boards are supported?

Besides generic CORE target for STM8S003F3P6, there is currently support for the following boards:

I also ordered the following SmartClima control boards for tests:

@Elliot Williams worked on using the ESP-14 as an IoT deviced (the ESP-14 is an ESP8266 with an STM8S003F3P6 in a ESP-12 package).

Programmable power supplies based on the XH-M188, and a cheap DC/DC converter are work in progress. There are also several types of STM8S003F3 based voltmeters that can be supported.

Read more about likely future targets below.

Why Forth?

Again, because it's fun!

Consider this:

  • compared to other programming environments the core of Forth is easy to fully understand
  • like Lisp, Forth has a REPL (Read-Evaluate-Print-Loop) which enables software testing in a way impossible with "Edit-Compile-Run-Debug" (e.g. Arduino)
  • it's easy to build Domain Specific Languages (you can literally program the compiler!)
  • the stack-centered "factoring" approach provides implicit data flow which leads to maintainable code
  • Interpreter-compiler, basic OS functions fit in just 4K code :-)

Forth starts out as a stack machine with a tiny instruction set and minimal hardware requirements. It fits in a few KiB, and the target, even a lowly µC, can even be used as the development system. The Forth stack machine is a minimalistic VM on a standard CPU, but there are also hardware implementations (e.g. for FPGAs, or a 144 core Forth processor). The VM is ideal for fast context switching and Forth easily meets hard-real-time requirements. It's no surprise that Forth was used in many NASA projects.

A Forth programmer is in control of all levels of problem abstraction, a unique advantage in a world where layer on layer of 2nd hand solutions leads to ever growing complexity (compilers, libraries, operating systems, drivers,frameworks, IDEs... ). I'm convinced that "Thinking Forth" will make anybody a better programmer, not just in the domain of embedded control!

Why STM8S003F3 or STM8S103F3?

Low-end "STM8S Value Line" STM8 µCs are very cheap (less than $0.25 in hobby quantities, $0.20@100pcs)....

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stm8ef_v2.2.0.zip

The latest release is on GitHub. Release v2.2.0

Zip Archive - 18.94 kB - 12/04/2016 at 23:22

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2157_stm8ef.zip

Original version of STM8EFalong with docs as received from Dr. C.H. Ting on 21/Nov/2016. The docs are worth reading, the eForth binary will run on the STM8S Discovery.

Zip Archive - 21.97 kB - 11/21/2016 at 20:13

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  • 1 × ST-Link V2 ICP adapter (e.g. $2.00 from AliExpress) The ST-Link on an STM8S Discovery Board can be used, too
  • 1 × serial interface /w 3.3V level (e.g. a $0.60 CH340 USB adapter) e.g a CH340 USB interface
  • 1 × STM8S target device as listed in the GitHub Wiki (e.g. a $0.70 "STM8S103F3P6 minimal system board") e.g. "STM8S103F3P6 STM8S development board" from your favorite China source
  • 1 × Some headers, patchwires, breadboard etc (about $2.00)

  • Controlling 3 servos with STM8S103F3 (made simple)

    Thomas2 days ago 0 comments

    Library functions, and the upload utility in e4thcom with its #include feature make programming a STM8S103F3 demo board much simpler.

    Here is an example:

    #include utils/rammark.fs
    RAMmark
    #include regs/opt.fs
    NVM
    #include hw/opt.fs
    \ set option bits to enable PC5 TIM1_CC1, and PC6 TIM1_CC2
    : OptInit ( -- )
      OPT2 DUP C@ $01 OR SWAP OPT!
    ;
    RAMdrop
    RAMmark
    #include regs/timer1.fs
    NVM
    #include hw/pwm.fs
    \ timer1 init to 1MHz clock and 20ms period
    : ServoInit ( -- )
      15 T1PwmInit
      20000 T1Reload
      1500 PWM1  \ PC6 pin 16
      1500 PWM2  \ PC5 pin 15
      1500 PWM3  \ PC3 pin 13
    ;
    RAMdrop
    \ Done!
    \ run OptInit to configure GPIO functions **once**
    \ run ServoInit
    \ set servos with y PWMx | y: 1000..2000 [µs], x: 1..3

    This demo works with STM8EF v2.2.13.snapshot (the include files are in the lib folder).

    Steps for using it:

    • unpack the v2.2.13.snapshot binary
    • put servo.fs into the release base folder
    • install e4thcom, and put the e4thcom STM8EF extension into the release base folder
    • run e4thcom with e4thcom-0.6.1 -t stm8ef -d ttyUSB0 (or whatever your TTY is)
    • in e4thcom type #i servo.fs1

    Refer to the e4thcom docs for more information.

  • Pre-release v2.2.13: better W1209 serial with e4thcom support (and more)

    Thomas4 days ago 0 comments

    Connecting the W1209 is now really easy:

    It's no longer necessary to modify the W1209!

    It's been a while since the last release, maybe too many interdependent steps for speedy development. Anyway, most is now tested, and ready to use:

    • dictionary headers can be selected on a board-by-board basis (issue #32 )
    • make BOARD=xxxx forth target uses tools/codeloadTCP.py and uCsim for code generation with #include feature (issue #32 )
    • software full-duplex serial interface, e.g. for e4thcom (issue #41 )
    • board W1209-FD with full-duplex serial interface (issue #42 )
      • key "+" / PC4: RxD
      • key "-" / PC5: TxD
    • default HAS_ALIAS=1 allows immediate words in RAM while compiling to NVM (issue #43 )
    • a Forth library has been added to code repository, and binary release (issue #43 )

    Check out the GitHub Releases page (binaries are included).

  • One Year STM8EF, Build-Framework MVP, and a Forth Terminal

    Thomas07/02/2017 at 20:52 2 comments

    One year ago I published an initial version of STM8EF on GitHub. I was then a near total Forth newbie, and I had no idea where the journey would take me. In just one year STM8EF turned into a very lean but rather complete self-contained Tiny Forth with support for some super cheap Chinese boards with a small but active community!

    The latest additions are:

    • a Build Framework with include file support, that compiles Forth code into a target binary
    • a ucSim based µC simulation with a Forth console
    • upcoming STM8EF suppory in e4thcom
    • the very beginning of a library
    • a decomposable core (linking, and core word includes are optional)

    Future work will go in this direction:

    • better support for applications that require very high code density (e.g. hybrid STC/ ITC)
    • a library with basics like hardware drivers, math, etc (maybe in the form of packages)
    • more exchange with the Forth community
    • Script-Kits (sic) for typical applications (power supply, lab automation, why not thermostats ;-)

    One more thing that happened in just one year: I have to be super careful not to forget how it is not to be a Forther - otherwise the whole thing will be of very little use for the average HaD guy. I guess that there is a need for more spin-off projects that are really easy to build, and simple to understand.

  • A Fan Speed Controller

    Thomas06/28/2017 at 12:19 0 comments

    In the project's Issue section on GitHub, someone proposed supporting the "ZFC39" Fan Speed Controller.

    Check the link above, and join the discussion if you're interested!

  • Developing the Framework

    Thomas06/25/2017 at 13:13 0 comments

    My project team here on HaD discussed requirements for a build Framework:

    • board support code in Forth should be part of the binary release
    • build, and test automation should possible for board support code
    • selection of core words should be possible on a "per board" basis
    • Forth code should be stored either in library folders, or in the board folder
    • Uploading Forth code should be supported by an "include" feature

    Thanks to the active support of all team members, and of the author of uCsim (a component of the SDCC toolchain) we're now a great deal closer to this goal.

  • STM8EF v2.2.12: RigTig's Release

    Thomas06/16/2017 at 12:23 0 comments

    After one year of STM8EF development this release marks an important point: a community begins to form!

    • @RigTig contributed code that replaces the dictionary (and most of the compiler code) in Flash with Alias definitions and code in RAM (refer to issue #26 and barebones.fs). All the necessary build switches are in the master branch.
    • RigTig reported issue #28: COMPILE sometimes failed when dealing with words in RAM. This is fixed.
    • The COMPILE fix was more than compensated by binary size reductions CORE is down to 4040 bytes (from 4087), MINDEV fits in 4963 bytes (5005 before). Guess who spotted potential for optimizations...
    • Better comments (issues #36, #34).

    Thanks to all contributors for code, comments, and bug reports: @RigTig, @Elliot Williams, @Roy

  • More Good Testing, Bugs Fixed, uCsim

    Thomas06/15/2017 at 16:09 0 comments

    @RigTig found a very nasty bug that only bites advanced Forthers: the STM8EF compiler uses CALLR (2 bytes) instead of CALL (3 bytes) when called words are within reach of relative addressing. However, the COMPILE instruction, that's normally used in "immediately executed code" (the kind of code in which the Forth compiler is written), assumes that a 3 bytes (absolute) CALL is used. It took a while until I understood what's the issue. Thanks for the patience!

    The bug is now fixed, and the additional code was compensated by optimizations (the binary size is still the same).

    When I fixed the bug I used uCsim by Dániel Drótos. The latest development version of uCsim has UART support and the MINDEV, CORE, or STM8S105K4 binaries work out of the box (this also means you don't need hardware for testing STM8EF).

  • Release v2.2.11: Board XH-M188, ALIAS Feature

    Thomas06/04/2017 at 12:09 0 comments

    Board XH-M188 (Issue #29)

    @Elliot Williams contributed initial support for the board XH-M188. Thanks a bunch!

    After removing the socketed 7S-LED display the board offers a GPIO breakout, and standard RxD/TxD communication ports.

    ALIAS Feature (Issue #26, #27)

    @RigTig needs more free Flash memory for his main project. As Forth headers require a lot of memory he proposed loading Forth headers to RAM. With the help of some minor changes to forth.asm (e.g. enhanced NAME>) about 2000 bytes of Flash memory can be recovered. Please refer to the discussion in #27.

    Words last and NAME> used in RECURSE example linked

    The recursive programming example requires last and NAME> to be exposed. That's fixed now.

    Binaries are here - Happy hacking!

  • Pushing the Limits: Beyond STC Forth

    Thomas05/28/2017 at 10:49 0 comments

    @RigTig has a very ambitious project: build a 3D printers for very large objects (e.g. a house) from almost nothing. STM8EF is a good match: it builds a programming environment for almost nothing (i.e. a STM8S003F3P6 µC). While the current code is already rather good, it needs to get better to meet RigTig's requirements.

    Issue #27 on GitHub discusses use case, requirement, and solutions:

    • Introduce assembler features
    • Extend the compiler (tail call optimization)
    • Introduce the ALIAS word class
    • Mix STC with DTC (using ALIAS words), or ITC (using a Inner Interpreter)
    • Malleable dictionaries
    • and more

    If Java is like coffee to make you type faster then Forth is like LSD which makes you see solutions in the fractal complexity of the universe!

    EDIT: RigTig used the alias method to create a lean-and-mean configuration for the W1209 board: it fits in about 3.5KiB code, almost 2KiB less than the normal W1209 variant, LED display code included!

    Check it out here.

  • Better Docs for the Relay-4 Board

    Thomas05/14/2017 at 17:47 0 comments

    The C0135 "Relay-4" board has 4 relays (duh), 4 inputs, and is based on the STM8S103F3P6 (the lower spec STM8S003F3P6 would have done the job just as well).

    I now updated the docs in the GitHub Wiki, and added some example Forth code that demonstrates how to use it as a heating / neutral / cooling temperature control (as if there wouldn't be enough Chinese STM8S003F3P6 based thermostats boards).

    By the way, right now this board is available on AliExpress for just $7.67, which isn't a bad price for a "Nano PLC.

View all 77 project logs

  • 1
    Step 1

    Get some cheap hardware (e.g. a STM8S103F3P6 breakout board for $0.65 and a ST-Link V2 dongle for $2). download the binary release, flash it, and have fun!

    If you like it, and you want to hack board support code for your favorite STM8China gadget, you need:

  • 2
    Step 2

    a Linux SDCC tool chain installation (installation instructions for SDCC & stm8flash are in the Wiki)

  • 3
    Step 3

    Clone the project on GitHub

View all 4 instructions

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Discussions

richard wrote 5 days ago point

My first attempt at using a W1209 board has been very rewarding. A couple of suggestions for anyone starting out and for the project team:

 

1. I had no success flashing the board with the suggested ST software on http://www.st.com/en/development-tools/st-link-v2.html.  You may also consider the ST software used by the person who published the schematic of the W1209. It can be found at http://www.st.com/en/development-tools/stvp-stm32.html

 

2. When putting the header on for the SWIM connector use 5 pins instead of 4. The 5th pin is a convenient place to tie one end of the diode to for the half duplex link.

 

3. While the SWIMCOM binary may work on the W1209 board, for the newcomer there is a lot of reward in seeing the "4th" string on the LED display once the binary is flashed. With that feedback you know it is just a matter of getting the serial comms to work.

 

4. With the extra pin the SWIM connection would be a much better place to have half duplex communications. It would prevent the serial communication from disrupting measurements on the sensor pin while debugging and gives you a pin that your push on connector holds better.

 

5. Is there a place to share code snippets? For instance, I wanted to blank the display before sending another character to it. I used

 : Clrdisplay \ clear anything showing

        32 E7S 32 E7S 32 E7S ;

 

I also wanted a delay between displaying “On” and “Off”. I used the following but I suspect there is an easier way:

VARIABLE timer

variable bigtimer

 

: tSet TIM 1000 + timer ! ;

: tTest TIM timer @ - 0 < ;

: delayInner tSet begin ttest until ;

: delay 0 bigtimer ! begin delayInner 1 bigtimer +! 25000 bigtimer @ - 0 < until ;

 

If there was a way to share these snippets it may prove useful to the newcomer. Maybe I just don’t understand the features of github well enough *grin*.

 

Anyway, I can recommend this forth implementation to anyone looking to hack one of these boards. I’m having a blast . I only wish I had found about this project before I built my electric gate controller with an atmel avr chip programmed in assembly. I could have just brought a cheap relay board and achieved the same thing without having to fabricate a board, populate it then program it in assembly.

 

Keep up the great work team.

 

Kind regards

Richard

  Are you sure? yes | no

Thomas wrote 4 days ago point

Hello Richard, thanks for your comment, it's higly appreciated!
Here are a few pointers to related actions, some new, some in the making.

1: the Wiki is updated https://github.com/TG9541/stm8ef/wiki/STM8S-Programming

2, 3, 4: using a 5-pin header and a diode is a good idea! I'm currently experimenting with using the W1209 key GPIOs (PC4, PC5) for full-duplex communication, which has several advantages. What do you think?

The usability of STM8EF programming is currently under active development.   Especially a. and b. should be helpful for new users:

  a. improved full-duplex serial code, e.g. for W1209 https://github.com/TG9541/stm8ef/issues/41
  b. e4thcom support with libraries
  c. temporay "scaffolding" code in RAM
  d. board hex file generation in uCsim

5: I created a GitHub Gist with your code snippets - let's see if that works as advertised: https://gist.github.com/TG9541/69fa106e88f8ca3a482a79e572c45463 

I created an issue on GitHub https://github.com/TG9541/stm8ef/issues/42
It would be great if you could contribute to  taking the decisions for a better W1209 support. Also feel free to open an issue on GitHub for topic oriented discussion.

Thanks again for your contribution.

  Are you sure? yes | no

richard wrote 4 days ago point

Thomas,

great stuff. I've been at it all day so real life drags me away for now. I don't have much to contribute on full or half duplex serial. I used Teraterm and slowed it down (25ms each character, 500ms for each line return) so the compiling could keep up. I was happy with that.

The Github Gist is interesting. Over time it could be really useful. Perhaps the main Github wiki needs to alert readers to it's existence?

I'm happy to help out with the W1209 where I can. You've no doubt heard of the saying "the blind leading the blind". 

The W1209 is a great platform and it is very exciting to think that much of what I used F-PC for years ago I could do on something costing so little. I plan to contribute as much as I can. 

Regards

Richard

  Are you sure? yes | no

Thomas wrote 4 days ago point

Richard,

the voice of users is important, especially in a hobby project where there is no such thing as "market research" - users know very well what makes a product  useful for them. One I'd like to figure out is if connecting a serial interface to the keys "+" and "-" is acceptable (the keys will remain usable), at last during interactive programming. The other thing is whether support for "sensor header COM" needs to be maintained, or if I can simply replace it with something better :-)

  Are you sure? yes | no

Thomas wrote 4 days ago point

FYI: issue #41 is closed (which means that full duplex communication now works without character delays). I'll make a pre-release.

EDIT: please check the project log

  Are you sure? yes | no

RigTig wrote 02/27/2017 at 21:59 point

Thomas mentioned that a better file loader would be nice. Here is my attempt. Simple to start with, but obviously capable of being expanded with features later. It is in Python2 and runs from the command line of the host machine (mine is LinuxMint).

<code>

#!/usr/bin/env python2

import serial
import sys
import time

port = serial.Serial(
    port='/dev/ttyACM0',
    baudrate=9600,
    parity=serial.PARITY_NONE,
    stopbits=serial.STOPBITS_ONE,    
    bytesize=serial.EIGHTBITS,
    timeout=5)

if len(sys.argv) < 2:
    print('Usage %s ... [fileN]' % (sys.argv[0]))
    sys.exit()

def upload(path):
    with open(path) as source:
        for line in source.readlines():
            time.sleep(0.2)        
            line = line.strip()
            if not line: continue
            if len(line) > 64:
                raise 'Line is too long: %s' % (line)
            print('\n\rsending: ' + line)
            port.write(line)        
            port.write('\n\r')
            chin = ''
            response_buffer = []
            while chin <> '\v':
                response_buffer.append(chin)
                while port.inWaiting() > 0:
                    chin = port.read(1)
            response = ''.join(response_buffer)
            sys.stdout.write(response)

for path in sys.argv[1:]:
    print('Uploading %s' % path)
    upload(path)

</code>

Usage: Save this code as a file (say named loadserial.py) and change its permissions to be executable (just the lines in between the code tags). I put loadserial.py in my local /bin folder. Edit loadserial.py so the port matches what you use when using a terminal console to connect to STM8 machine.

WARNING: I've just noticed that the indentation was inconsistently displayed, and python is indentation sensitive. So be very careful with just copy-and-paste. I'll put a copy of it up on RigTig's Big 3d Printer project here on hackaday.io.

Either put FILE on first line of the file to be sent, or type it into a terminal console and close it, then use a local command line interface thus: <code>  filename file2send </code>. Enjoy!

  Are you sure? yes | no

Thomas wrote 02/27/2017 at 22:26 point

Hi RigTig, this is cool! Now the last reason not to learn Python (the haploid language, as I use to say) has gone. I'm going to need it in my job, anyway ;-)

PS: I just added the tag v2.2.8.1.snapshot, and this means that the binary size of CORE is below 4096 bytes, complete with the new "transparent" VARIABLE feature

  Are you sure? yes | no

Thomas wrote 03/04/2017 at 11:07 point

I just tried your loadserial.py script - the handshake seems to work, and compiling code to NVM is very fast compared to the "worst case delay" method!

However, I had to interrupt the script with ctrl-c after the transfer was finished. The reason was that my Forth code ended with "HAND", after which loadserial.py waited in vain for the handshake signal.

I can imagine that an improved uploader does the following:

* handle FILE and HAND (no need to include those in source file), or

* terminate transfer when the response is anything but the handshake character

The next thing on a programmer's wish list is a way for including source files (nested, of course). I can also imagine testing if "base code" has already been transferred, e.g. using some query-response between the Forth system and the uploader.

  Are you sure? yes | no

Thomas wrote 02/27/2017 at 22:26 point

Hi RigTig, this is cool! Now the last reason not to learn Python (the haploid language, as I use to say) has gone. I'm going to need it in my job, anyway ;-)

PS: I just added the tag v2.2.8.1.snapshot, and this means that the binary size of CORE is below 4096 bytes, complete with the new "transparent" VARIABLE feature

  Are you sure? yes | no

RigTig wrote 02/23/2017 at 05:44 point

Thanks Thomas for a great environment in which to have lots of fun. I needed VARIABLE to be defined in NVM, but to keep its data in RAM. Some variables need to change for every data line processed (megabytes of GCODE), so using NVM is just not going to cut it for real use. Besides NVM access is slow. So, here is my replacement definition for my project:

: variable create here , 2 $6e +! does> @ ;

Now, this works only in NVM mode, because it makes no sense to use it in RAM mode anyway. Besides the DOES> part would be wiped every COLD or restart. The magic address of $006E is the address of next available RAM when in NVM mode.

If you want to test after a restart or COLD, you need to adjust the address of next available RAM to be after the last used address by a variable. In my case, the last used address was $009e. Note that in RAM  mode, the address of next available RAM is at $006A. So, I typed

$a0 $6a !

and then initialised all variables and they just work. Now this hack is not for every project (obviously), but does show what can be done when a need arises. Enjoy!

  Are you sure? yes | no

Thomas wrote 02/23/2017 at 21:35 point

Hi RigTig! That's indeed a nice hack, and it is much along the lines of what I had planned.

I'd like to propose the following solution: 

1. some memory below the user dictionary in RAM shall be set aside by adjusting the reset value of USRCP
2. the next variable address for NVM routines shall be stored in the (new) variable USRVAR, which shall be initialized from USRCP
3. when switching from NVM to RAM the reset value of USRCP shall be set to the value of USRVAR

I'd like to check if it's possible to make VARIABLE work transparently in NVM and RAM mode. Most likely writing a different word is easier.

  Are you sure? yes | no

RigTig wrote 02/24/2017 at 04:09 point

Thanks for compliment. I haven't really tried to make VARIABLE work in both RAM and NVM, but I am sure it'd work. The key is just understanding that there is one level of indirection (address of value instead of value), so RAM variables use an extra 2 bytes over the non-indirect version. Nice to avoid wasting ram, but not really a show-stopper. Coding in assembler should be far more memory efficient than the Forth version, but it's the joy of Forth to be able to do these kinds of things at all (and optimise later when you find that it is really a good idea!).

A hard reset or even COLD needs to preserve the ram space needed by variables, but I prefer not to lock in a pre-determined limit on the number of variables. I also hate wasting valuable resources by committing them for just-in-case scenarios. 

So let's consider the use cases. Is there a need to support programming to NVM, then RAM, and back to NVM? If we say that all NVM variables need to be defined before RAM gets any code, is that reasonable? At least all the ram needed is in one block in this case. Probably a bit hard to communicate to programmers, and practically impossible to enforce.

Even if there is some code compiled into ram before or after NVM variables are created, the only thing needed is to set the ram space used for parsing commands to be above the last used ram for any variable. This happens anyway until COLD or hard reset. Maybe all that is needed is a persistent vector stored in NVM to be used instead of the $0080 for start of ram space for code and variables. Now the incentive is for the programmer not to waste space, so it becomes 'obvious' that defining all NVM variables before using ram for anything else is just better management of the limited ram. VARIABLE needs to update the persistent vector each time, based on current ram pointer. Variables defined in ram waste space after a COLD, but that might just be a price to pay (and is quite ok during interactive development, methinks). Mmm... and RESET needs to reset the vector to first available ram for code and variables back to its compilation default ($0080).

I am sure to have missed something in this ramble, but hey, that's what hacking is about isn't it? If I knew what I was doing, then it is not real hacking! And what other language allows you to play around with how the language itself works, so Go Forth.

  Are you sure? yes | no

Thomas wrote 02/24/2017 at 06:41 point

RigTig, we're on the same page :-) 

If you read me previous comment carefully you'll find that the "machine" needed for implementing is mainly coded in the difference between "the reset value of USRCP" and "USRCP" (there is one error though: point 2. should be "in the new variable USRVAR which shall be initialized from the reset value of USRCP"). 

One could argue that this means waste of RAM, but actually it's just a buffer for certain use cases. You already mentioned some uses cases, and how much they would "surprise Joe Programmer".

My model for the programming workflow is this:

1. start a session with COLD, reset, or flashing the µC

2. write some test code in RAM (i.e. do the things you'd normally do with the original STM8EF)

3. run COLD and set the stage (e.g. define helper words like here: https://github.com/TG9541/stm8ef/wiki/STM8S-eForth-Programming#low-level-interrupts-in-forth)
4. run NVM, define words, variables etc as you like

5. run RAM, make pointers to the newly defined words, and also to USRVAR persistent

6. return to 4. (write more persistent code) or to 2. (test your code, preferably automated)

Of course, the casual user may miss the finer parts of the "Stage/NVM/RAM/Test/COLD" cycle, but they will notice quickly that words defined in RAM can't be compiled-in (only interpreted) in NVM, and that code compiled in NVM is lost if they forget to run RAM.

As you pointed out, a certain coding style, like defining variables first, isn't difficult to get used to. Setting aside a small buffer (e.g. 32 bytes) as a variable space wouldn't be a big deal, and it would enable the "setting the stage" use case without the risk of immediately overwriting words like IVEC. It's of course also possible to cycle through the steps 2..6 more often (also as a part of the source code) , but a buffer would add some flexibility. In the extreme case (use many variables, use a huge stack), writing test code in RAM would suffer. But hey, when testing words one tests the units, not the whole program where the stack reaches its maximum size.

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Thomas wrote 02/26/2017 at 09:35 point

@RigTig

Please have a look at this: https://github.com/TG9541/stm8ef/tree/variable

The new code has the features discussed above. The behavior of VARIABLE and ALLOT is transparent in NVM mode, and in most cases there is no need to manage RAM allocation. Only if one allocates more than 32 byte RAM in a session it's necessary to cycle through COLD before using variables newly defined in NVM mode.

Edit: preliminary documentation of the new feature is here: https://github.com/TG9541/stm8ef/issues/16#issuecomment-282547170

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RigTig wrote 02/27/2017 at 01:08 point

Thomas, I have to say that your approach is just brilliant. I love the idea of being able to just get more variable space if needed, and not wasting any ram either. 

P.S. We might be both on the same page, but I'm only partway down. I am still getting my head around the STM8EF code. I keep going back and changing the options for a new flash image and it is installed in a second or two. What fun to play with!

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Thomas wrote 02/27/2017 at 07:17 point

@RigTig: thanks for your support! I just pushed a "size reduced" revision to the variable branch. Since I had to do some shuffling, some "review" and "testing" by "an independent person" would be great (in a hobby project that's what's known as "playing with the code" :-)

Currently some RAM gets wasted, but that could be bettered by giving the programmer control over the headroom for RAM allocation (which would be easy).

By the way, I ordered two of the radio modules you've been working on.

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Elliot Williams wrote 01/23/2017 at 08:55 point

Hiya Thomas,

Got an ESP-14-powered device up and running and installed in our basement.  Long story, must write up.

Have you played around with power saving modes on the STM8?  I'm trying to get the part into the AWU / active-halt mode.  

For one, I need the assembler's HALT command, which I've been doing in the worst brute-force means possible: HERE $8e81 , EXECUTE.  (That's HALT and RET in machine code.)  

It halts, at least.  :)  

Coming back out of halt is messy -- it looks like the clocks aren't returned to their original states and so on. I'm probably going to need to implement some start-up code.  Heck, for my purposes, hooking into COLD for a complete reset will work too... That's what I'll try next.

Just wondering if you've worked on any of the low-power modes.  Either WFI (wait-for-interrupt) or the active-halt/AWU look tasty.

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Thomas wrote 01/23/2017 at 19:14 point

That's great :-)

The power saving modes (like the watchdog) still are on my "important things that I plan to do" list. You know, that's the list on the sheet after "new and exciting things I want to play with", which in turn comes after "bugs I must fix now".

Let's put it on the "important new features for pilot applications" list :-) 

What we need is:

* a word HALT that contains the HALT instructionknow

* a word SLEEP, that stops unnecessary interrupts (user defined, and application specific). This word should run HALT. When the execution continues right after HALT, SLEEP shall re-enable "waking" interrupts

* if required a word to restore clock settings (RM0016 mentions something in 10.2.2 and in 9.9.4 "Clock master switch register (CLK_SWR)", but right now I don't undertsand why the clock changes)

Do you plan to trigger a wake-up through console events? The simulated COM port should support this use case!

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Thomas wrote 01/23/2017 at 19:45 point

I added the HALT word, and it works better than expected. Here is a demo with a blinky:

    : g tim 40 and 0= out! ; ok
    ' g bg ! ok
    HALT
The when I press enter after HALT the LED stops flashing. The "ok" after HALT appears after I press enter a second time.

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Elliot Williams wrote 01/24/2017 at 11:52 point

Woot!  

re: clocks: I read something somewhere sometime about them needing a reset.  I can't find that anymore.  I may be crazy.  

I saw some other STM8 code (http://blog.mark-stevens.co.uk/2014/06/auto-wakeup-stm8s/) that runs the AWU without re-clocking, strongly suggesting that I'm crazy.

That code, though, makes it look like (if interrupts are enabled) the AWU reset lands in the AWU ISR, which is uninitialized ($0000) in the vector table at $800C.

I just ran your BG example above, and it halts, but never returns until hit with a hard reset. I wonder if your code is working b/c it NOPs off to the next ISR and you got lucky.  Or does it actually try to execute whatever's at $0000?

So: how do we set up ISRs in eForth?  (Or, how do you write bytes directly to flash?)

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Thomas wrote 01/24/2017 at 19:23 point

TL;DR: the quick-fix: an AWU "driver" that does it all but I would prefer a Forth solution and this requires some design decisions.

Long version:

Due to limitations in the SDCC tool chain any interrupt must be declared in main.c. Writing ISR vectors to Flash might work, but it requires a good approach for registering (and unregistering) interrupts to be viable (I'm thinking of RESET). Also Forth VM context switching would have to be done before executing any Forth code.

Another approach would be a "catchall" interrupt handler for several interrupts that then redirects to Forth code. This has the advantage that the context switch can be handled in a uniform way, but the dispatching won't be very efficient (or again a lookup).

This brings us to the next problem: some interrupt sources require resetting some bit in some peripherals control register. Leaving that to user code is very error prone, and a "catchall" interrupt handler would have to do it for all possible sources or leave it to user code.

What do you feel about of a middle way?
* Interrupt handler declared in main.c
* basic handler code in assembler or c to do a context switch, and to clear the trigger source
* handler code in Forth registered through something like BG

A last point: how many concurrent "Forth code interrupts" can we allow?
* Level0 we have the console
* on Level1 is the BG interrupt
* on Level2 is TIM4 (for COM simulation)

I guess that some stuff like TIM4 shouldn't have to compete with other code (the current code is efficient as it gets). Most likely it's possible to drop the interrupt level in BG code to Level0, and use Level1 for Forth handlers without character-I/O. The latency would still be in the lower µs range.

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Elliot Williams wrote 01/25/2017 at 12:43 point

How does the 'BOOT mechanism work?  If you could do placeholders for the various ISRs like that, the user could write their handler function and store its address in the right place?  That seems very Forthy to me.  <code>: awu-isr stuff ; ' awu-isr ISR_AWU ! </code> or something.  One of these functions / memory locations per IRQ and you'd be done?

On resetting the flags as you leave the ISR: I think that should be user code rather than bloating up the system with it.  Yeah, it's going to hang the system if you do it wrong.  If I could count the number of times I've pressed the reset button...

On context switching in ISRs:  I'm not sure I understand the full details.  Unlike C, there's not necessarily any context to switch?  If the ISR maintains stack balance then there's no need for any context?  Leave whatever's on the stack, and it'll still be there when the interrupt is done?

For me, personally, I'd just be stoked to have a pointer to an address that I could set to execute when the AWU IRQ fires.  The rest, I can handle in code, I hope. :)  (Assuming that the return from interrupt works right.)

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Thomas wrote 01/25/2017 at 20:20 point

'BOOT is simple: it returns the address of the "Parameter" field (like DOVAR). To safe code I used it to get the address of the whole following table of initialization values for USR variables. After switching to "NVM" it's possible to simply overwrite all these values. There is a 2nd copy to restore these values, e.g. to "forget" user vocabulary in Flash memory with RESET.

Yes, the 'BOOT method can be used in for interrupts, too, but that would require one more level of indirection.

About context switching:

my first approach was to re-use the Data Stack, but I quickly learned that X isn't always a valid Data Stack Pointer: it does that at the start and the end of a word, but not always in between ("always" is a very important attribute when writing interrupt code). Before implementing the background task, I tried  to make sure that X always represents a valid stack pointer in all primitive words. However, I failed to get it working until I started using a 2nd Data Stack for the background task (which I didn't like since it appears wasteful). Later on, I applied coding techniques that use X for reducing code size. Of course, it's possible to re-factor the code. It would be interesting to compare other multi-tasking Forth implementations. 

I went in a different direction: In several refactoring rounds I removed the following variables entirely: TEMP, XTEMP, PROD1, PROD2, PROD3, CARRY, and I also made the I/O context leaner.

Now, for code without character I/O only YTEMP must be saved. Otherwise also BASE, PAD, and HLD must be taken into consideration. And, of course, we need a stack. One approach would be to have a floating "stack pad" to work around the "X!=TOS" problem.

I guess it will take some time to implement a full featured solution for Forth interrupt handlers.

A minimal solution might look like this:
* a word IVEC! to set an interrupt vector
* a word SAVEC to save the context
* a word RESTC to restore the context, ends with IRET

The application could then define a word in the following way:  

: handler SAVEC ( some stuff ) RESTC ;

 ' handler 1 IVEC! \ set the AWU interrupt handler

Now that I'm looking at it, this doesn't look too bad.

Edit: I made some corrections, added some details, and added one more option for a solution

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Thomas wrote 01/25/2017 at 22:23 point

I added the solution above for testing to the develop branch. Due to the mentioned limitations it's currently necessary to initialize the interrupt to priority low (0:1) (it shares the data stack with the ticker).

I also changed TIM4 to prio "highest", which might allow to implement all user defined interrupts with priority "high" later on. This would then require 3 data stacks with the sizes normal (console), medium (background task) and small (interrupt handler).

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Thomas wrote 01/26/2017 at 20:48 point

@Elliot Williams:

Here is a starting point for Forth code user interrupts and AWU usage:

  nvm

  : awuint savec awu_csr1 c@ drop restc ;

  ' awuint 1 ivec!

  : initawu 38 awu_apr c! 1 awu_tbr c! 16 awu_csr1 c! ;

  ram

When I run HALT with this code, it returns immediately. Since I didn't find the time to make sense of the AWU configuration, I simply took the AWU timing values from the page you mentioned before.

Please not that this currently only works when I run HALT from the console (I still need a solution for the Data Stack problem). Running HALT from the background task would change the contents of the first element on the stack (which would work if the stack were empty).

A quick fix here is to assume that X represents TOS when HALT is executed (which is the case), and skip initializing the stack. Please note that this only works for HALT, and not in the general case.

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Thomas wrote 01/23/2017 at 21:51 point

Changes are in the develpp branch on GitHub. The 2.2.6.snapshot release contains new binaries :-)

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Youlian Troyanov wrote 01/26/2017 at 04:51 point

please write your long story about esp-14 :)

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Thomas wrote 01/27/2017 at 22:19 point

Elliot, in order to get a simple and practical solution, I now propose the following:

1) In RAM code IVEC! (its only used once for setting an interrupt handler

: IVEC! ( a n - -  ) 2* 2* $800A + ! ;

2) Implement HALT as a user word:

: HALT  ( -- ) [ $8E C, ] ;

3) Implement your interrupt handler using SAVEC and RESTC (make sure not to use more than 8 cells on stack)

This will work for any interrupt. Please make sure to change the interrupt down from highest to high.

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jaromir.sukuba wrote 01/23/2017 at 05:17 point

Another tip for *possible* STM8 target http://www.ebay.com/itm/12V-DC-Multifunktionsrelais-PLC-Cycle-Timer-Timing-Delay-Relay-Switch-Module-/131648915593

I didn't buy this one, haven't seen the schematics, but to me it totally smells like it could have STM8 under the display. Googling for XK-001T-1 didn't bring much info, though.

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Thomas wrote 01/23/2017 at 06:18 point

Yes, that's possible. In most cases one won't find any schematics, and also the XH-, XK, M- or B monikers aren't always used the same. There is a small list of modules that are very likely STM8S based in the Details Section of this project (in the section "How can I spot suitable boards?"). If there is any interest, I can publish a list with advertised properties and the "street price".
Edit: here is a link with a picture showing the PCB legend:
https://www.aliexpress.com/store/product/Free-shipping-XK-001T-1-DC12V-Time-relay-board-count-voltage-testing-cycle-time-vehicle-charging/1548016_32656999267.html
Based on the outline of the µC I would expect it's not STM8 but a STC15 based, a µC which I've seen several times on "timer" boards (MCS51-like http://www.stcmcu.com/datasheet/stc/STC-AD-PDF/STC15-English.pdf)

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Elliot Williams wrote 12/13/2016 at 23:13 point

Got my ESP-14 up and running last week, and then got distracted.  :)

Short story: it's just a STM8 chip and an ESP8266, like it says on the package.  The TX/RX lines are internally connected, so I was running your Forth on the STM8 with the ESP8266 powered down, and running all manner of software on the ESP with the STM8 powered down.

Been thinking about how to use both at once. 

a) Jeelink is a nice transparent serial port over ESP8266, which would provide remote wireless development of the Forth system on the STM8.  The idea of telnetting over WiFi into an STM8 is funny enough that I'm definitely going to do this.

b) Since the serial port is the only way in to the ESP8266, and the STM8 has only that one hardware serial port, I suppose that bit-banged serial or I2C/SPI could be used to talk to the console. I don't know how hard/easy this is. But then you'd have an STM8 that could issue AT WiFi commands, for instance, or run routines in NodeMCU, which might be very cool.

c) The other option is to code up the ESP and STM8 to take turns based on control characters: 0xFE toggles the ESP on/off the line, and 0xFF toggles the STM8, for instance.   This requires modifying _both_ firmwares, but would allow for the console, ESP, and STM8 to share the UART lines and talk to each other.

Just brainstorming so far. No real hacking yet. 

The breakout board I made for the module just fit it onto a breadboard, because I didn't really know what to expect from the module. It will probably want a transistor so that the STM8 can turn off the ESP8266 for power-saving when necessary, and will certainly want at least a jumper for flashing the ESP.  

Thanks for the case insensitive addition, and for do loops! This is a fun system to play around with.

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Thomas wrote 12/14/2016 at 19:31 point

Options a) and b) look good to me, especially in combination. How about connecting a PNP transistor for the ESP8266 power supply to PD1/SWIM? Normally one would access the STM8 serial port through ESP-Link, and the ICP interface could be used for direct access to the ESP8266 serial interface by simply pulling down both NRST and PD1/SWIM. Direct serial access to the STM8 could be acchieved by telling it to power the ESP8266 down (this might even work using PD1/SWIM once more, e.g. by using an RC element which can be detected testing its timing).

Option c) would also be possible, but at least one of the devices would have to be able to swap RxD and TxD, and the other devices would need a "tristate" mode on TxD. The Bus approach I took for the W1209 might also work for more than two devices.

A fourth option could be to have a Forth word that issues the initialization AT commands on the STM8, and execute it with 'BOOT.

I hope to find the time for some hardware hacking in the holiday season :-)

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Elliot Williams wrote 12/16/2016 at 21:22 point

"esp-link" not jeelink.  https://github.com/jeelabs/esp-link  Tried it and had a telnet / web-console controllable STM8 running your Forth.  Took like 10 minutes.

Then I spent 3 hours trying to implement something like c) in NodeMCU.

First, I thought I'd set up two TCP connections: one for the ESP to be executed locally, and one to pass through to the STM8.  Didn't work b/c NodeMCU can only do one TCP connection, it seems.

Then I thought I'd use MQTT as the transport mechanism.  But there's some glitch there with MQTT and the UART port not working right.  I'll hack more at it before I give up, but it might be time to move on to MicroPython or ESP Basic for the interactive ESP part.

Anyway, try out the esp-link for the ESP when you get around to it.  It's kinda fun.  It _does_ however leave me wanting a more capable microchip on the remote end.  For another couple bucks, I could get a lot more flash, peripherals, and etc to tether to the ESP.

All of this playing around has helped me refine what's needed in a breakout board for this thing, though.  :)

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Thomas wrote 12/16/2016 at 22:35 point

Again great news, and I'm going to test esp-link too. Multiplexing communication through MQTT topics was the first thing that came to my mind. About a year ago I tried working with MQTT and NodeMCU, but I was disappointed with the stability of the platform (though I really liked working with Lua).
I guess that the case for ESP-14 is rather thin: as I mentioned before, it looks more like proof that the ESP8266 wasn't able to meet customer requirements than like the solution the world's been waiting for. But who cares as long as it's fun hacking.
In my opinion, a decent Forth environment on the ESP8266 would be rather attractive: C.H. Ting hacked something recently, but it was just the kernel, not a complete framework with persistent vocabulary (and maybe even with source stored in the Flash memory, and maybe even a JavaScript based IDE served from an embedded web server on the chip).

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Thomas wrote 11/28/2016 at 21:33 point

Hi Elliot, it's great to hear that someone got it running, and that the docs were good for a smooth start. Anyhow, congrats for the "STM8EF Blinky"! Did you try to do that BG style, too? 

I had a look at the CAPS issue (yes, I've been thinking about that for a while ;-) ). There are some potential clashes (e.g. PARSE/parse, NEXT,next, ABORT"/abort") but the lowercase words are the hidden "implementation part", and I don't see that their name is set in stone. I decided to name them after their assembly labels (pars, donxt, and aborq). 

New code with lowercase support is on GitHub (just set CASEINSENSITIVE = 1 in globconf.inc). If you'd like to give it a try without building, please let me know (I can drop a binary into the files section here). If there are no issues I'll make it the default.

The ESP-14 will be one of my next targets. However, I didn't find the time to make a breakout PCBs with power supply for this module. Controlling the ESP8266 supply through the STM8S003F3 would be cool. If someone with good access to PCB prototyping could do that job I'd be more than happy to contribute some ideas about the schematics.

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Elliot Williams wrote 11/29/2016 at 15:57 point

I just got an ESP-14 in the mail from ebay today.  I'll be making a breakout for it sometime in early Dec.  (Right now, I'm churning out HaD articles like mad.)  I'll share when I do.

I still have no idea if it makes any sense to run a (powerful) ESP8266 off of a (much smaller) STM8 chip.  But I'm willing to find out.  :)

I also ordered one of those LED/relay boards. Again, just for fun, but maybe I'll do something with it.

Thanks for thinking about caps.  I'll definitely rebuild and reflash. 

No, I didn't get into the multitasking / backgrounding. I just got the thing up and running, not much more.

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Thomas wrote 11/29/2016 at 19:13 point

The ESP-14 is quite strange. I can only guess that an OEM required a solution from Espressif that meets non-functional constraints (e.g. dependability, power consumption, or periphery set) that could not be met by the ESP8266. I don't think that a lack of skilled programmers was the reason. The power consumption of the STM8S003F3 in "active halt mode" is quite low, and for a data logging sensor node a battery life of a year or more with a 100mAh battery might be feasible.

The W1209 boards are really fun, especially with a background task. When you try using STM8EF with it, please let me know if the docs for the single wire half-duplex solution are sufficient.

About the case-insensitive input: you're welcome (the option has a price tag with "23 bytes" on it :-) )

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RigTig wrote 12/15/2016 at 10:44 point

I've created an adapter for ESP14 (and ESP12) to 22-pin DIL, if you haven't done anything else yet (see new project here called 'ESP-12 and ESP-14 adapter to DIL'). My ESP14s arrived today!

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Elliot Williams wrote 11/28/2016 at 13:54 point

Hiya! Been following along, finally got a few minutes to flash stuff to one of those min-dev boards.  Great fun!  I haven't done anything useful with it yet, but I've gotten the LED blinking, naturally.

One thing that's driving me nuts is the ALL CAPS commands.  Is there an easy way to either a) lower-case them all or b) make it run case insensitively?  Or would that cause namespace clashes? It makes my shift-finger hurt. 

And that's it for now.  I have to say that your directions (combined with some of the links that you list) made it very easy to get up and running with the system.  Thanks!

I'm planning a few Forth columns for HaD, and I'm still collecting chips that have working implementations.  You've added one more to the list. 

Oh, and I've ordered an ESP-14.  We'll see how that goes.  Looks like fun. 

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