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• Hackaday BASIC Interpreter

  Mike Szczys • 10/16/2018 at 16:21 • 1 comment

  The Hackaday BASIC interpreter is based on the uBASIC project by Adam Dunkels. This provided a tokenizer and the most rudimentary words needed for the language to operate. From there, Jaromir Sukuba greatly expanded the word set to take advantage of the best the badge hardware has to offer.

  We are also testing out an advancement in the tokenizer written by @ziggurat29 which shows a speed-up of as much as 40x!

  The reference for all of the words is listed below. You may also see examples of these words in use by viewing the example code project log.

  Of Note:

  • Code in the program buffer can be viewed one page at a time by typing more. You can overwrite lines just by typing the line number at the prompt along with your new commands. It is recommended that you number every 10 lines or more so that you can add commands in between them as you develop your code.
  • The memclr word will clear the code currently in the program buffer.
  • Always save before running in case you have to reset the badge. save 0 will save to the first of 16 slots, load 0 will load the saved code.
  • Press the BRK key to break out of a running program
  • Typing a line number without anything after it will delete that line from your program
  • There are two print commands. print will not include a line feed, println will include a line feed

  BASIC Word List:

  Standard Words:

  • print
  • println
  • if
  • goto
  • gosub
  • return
  • for
  • next
  • end
  • let
  • rem

  Badge Custom Words

  • led X,Y - control LED, X[0..2] RGB, Y[0..1] on/off
  • tune A,B,C,D - plays tones A, B, C for duration D
  • clrscr - clear screen
  • setxy X,Y - set cursor at X,Y
  • wait X - wait for X ms
  • color X,Y - X=Foreground, Y=Background using EGA 16-color palette
  • chr X - prints character with ASCII representation X
  • termt X - sets VT100 terminal on or off (1-on, 0-off)
  • termup - forces screen refresh, if VT100 terminal is off
  • rnd X - function to return random number 0..X
  • ein X - function to return value of expansion pin X
  • eout X,Y - control expansion pin, X[0..3], Y[0..1] on/off  (pin 0 is labelled "G2", 1="G3", 2="B0",  3="B1")
  • edr X,Y - sets expansion pin function X[0..3], Y[0..1] output/input
  • uin X - function to return received byte from serial port, if X=0, function is non-blocking, if X=1, function is blocking
  • uout X - outputs value X to serial port as single byte
  • input "string" - prints string and returns user entered value
  • peek X - returns value from memory location X
  • poke X,Y - write value Y into memory, on location X
  • cursor X - turns cursor on (X=1) or off (X=0)
  • kin X - function to return byte from keyboard, if X=0, function is non-blocking, if X=1, function is blocking

  BASIC CLI commands

  • run - runs program
  • save X - Save program buffer to flash. There are 16 slots: X[0..15]
  • load X - Load program into buffer from flash. There are 16 slots: X[0..15]
  • list - list whole program
  • more - list program by pages
  • memclr - clears all code from the program buffer
  • free - prints amount of free program buffer
  • sload - load new program into buffer from serial port
  • ssave - output program buffer via serial port
  • help - short help

  Aliases

  In order to save you some typing, we defined some aliases for functions
  

  • print - pnt
  • println - ptl

  • clrscr - cls,clr
  • input - inp
  • setxy - sxy
  • return - ret
  • cursor - cur

  Gotchas

  There are a few gotchas that you may run into if really go wild with your BASIC program. Here's a few to keep in mind for those who care to read them:

  • There...

  Read more »

• BASIC Program Examples

  Mike Szczys • 10/16/2018 at 16:21 • 0 comments

  Print out all possible characters:

  10 for i=32 to 255
  20 chr i
  30 next i

  Bling the LEDs randomly (d is diode [0..2], s is state [0..1])

  10 d = rnd 2
  20 s = rnd 1
  30 led d,s
  40 print “Press BRK to return to BASIC prompt”
  50 wait 100
  60 goto 10

  Play random Major triads:

  10 let i = rnd 77
  20 if i<53 then goto 10
  30 tune i,i+4,i+7,400
  40 goto 10

  Scroll some text. The space before the text erases the previous character in that position:

  10 let i=0
  20 color 14,12
  30 clrscr
  40 setxy i,0
  50 print " Scroller"
  60 i=i+1
  70 wait 150
  80 if i<32 then goto 40
  90 color 15,0

  Bounce ball on screen. Shows:

  • Moving to different areas on screen.
  • Changing color.
  • Using delays and subroutines.
  • Turn off the blinking text cursor with cursor 0.
  • Manual screen refresh (termt 0 shuts off automatic scanning, termup triggers manual refresh) for a smoother animation than the scroll text example.

  5 termt 0
  7 cursor 0
  10 let x = 39
  20 let d = 0
  30 clrscr
  40 color 11,0
  50 setxy x,10
  60 chr 32
  70 if d = 1 then gosub 200
  80 if d = 0 then gosub 300
  90 chr 254
  95 termup
  100 if x = 0 then d = 1
  110 if x = 39 then d = 0
  120 wait 50
  130 goto 50
  200 x = x + 1
  210 return
  300 x = x - 1
  310 setxy x,10
  320 return

  Function to read byte from serial port and print it out

  10 println uin 0
  20 wait 500
  30 goto 10

  This one starts printing zero every 500ms, if there is any incoming byte from serial port, it gets written out.

  If you change uin parameter from 0 to 1, function gets blocking, ie. execution doesn't continue until serial byte is received. In that case, only when byte is received interpreter prints anything out.

  The same example can be used to read data from keyboard, the function used is called kin.
  

• Music Syntax and Guide

  Mike Szczys • 10/16/2018 at 16:21 • 0 comments

  This badge has a built-in speaker and you can compose music for 3 voices using a simple scripting language. Use the BASIC interpreter to access these features with the syntax: 
  

  tune voice1,voice2,voice3,duration

  Duration is the number of milliseconds this chord should be held. The voice values use Scientific Pitch Notation (https://hac.io/hGf7) where middle C is 60. Do a C major chord held for 1 second would look like this tune 60,64,67,1000 -- below is a cheat sheet.

  PRO TIP: Remember BASIC programs can be saved in any of 16 slots (0..15) using the save/load commands.
  

  As an example, try typing this into your BASIC interpreter (you may want to type memclr before you start, to clear any existing code):
  

  10 tune 0,0,72,131
  20 tune 0,0,74,131
  30 tune 0,0,77,131
  40 tune 0,0,74,131
  50 tune 70,74,81,262
  60 tune 0,0,0,131
  70 tune 70,74,81,393
  80 tune 60,76,79,524
  90 tune 0,0,0,131
  100 tune 0,0,72,131
  110 tune 0,0,74,131
  120 tune 0,0,77,131
  130 tune 0,0,74,131
  140 tune 69,72,79,262
  150 tune 0,0,0,131
  160 tune 69,72,79,393
  170 tune 62,69,77,393
  180 tune 62,69,76,131
  190 tune 62,69,74,655

• Serial Communications with Badge

  Mike Szczys • 10/16/2018 at 16:21 • 2 comments

  Badge to Badge

  Remember those TI graphic calculators that had a cable to transfer programs? The badges can work in the same way.

  • Connect the GND pins on the expansion header.
  • Connect C14<-->C13 and C13<-->C14 on the two badges.
  • On receiving badge type "sload" and it will wait for program to arrive
  • On sending badge type "ssave". Program will be sent. Receiving badge will report 1 byte more than sending badge to indicate the zero terminator
  • Type list on receiving badge to see new code in the program buffer.

           IMPORTANT TIP: If the receiving badge doesn't react, reset that badge (shift-reset) and try again.                                                   Sometimes this is necessary after first connecting the cables.

  Computer-to-Badge

  A serial-to-TTL cable will allow you to communicate between the badge and a computer. If you own one of this cables we highly recommend you bring it with you! We will have cables on hand but it will be necessary to share them so extras are great!

  Wiring Diagram:

  • Badge Pin Ground (GND) --> Ground on serial cable
  • Badge Pin TX (C14) --> RX on serial cable (White in this example)
  • Badge Pin RX (C13) --> TX on serial cable (Green in this example)
  • Important: Leave voltage disconnected (Red in this example)

  Serial Connection Info:

  • Baud: 19200 8N1
  • In basic, use command ssave to send program buffer as string
  • In BASIC, use command sload to recieve string into buffer
  • CP/M includes xmodem. Check your computer's serial program to ensure it supports this protocol. In the Z80 Emulator, switch to b: drive and run command similar to this: xmdm r d:FILENAME.EXT

  Linux: Simple Instructions for Transferring BASIC Programs

  This quick walkthrough assumes that USB to TTL serial cable will enumerate as /dev/ttyUSB0. Look at dmesg output after plugging cable to ensure this is true.

  Setup simple Linux serial connection:
  

  Use dmesg and look for where the serial cable is mounted -- this example assumes /dev/ttyUSB0. It then sets permissions to that mounting point, sets the serial parameters to a "sane" value, and configures the port as needed. When in doubt, power cycle your badge and try again.

  sudo chmod 777 /dev/ttyUSB0
  stty -F /dev/ttyUSB0 sane
  stty -F /dev/ttyUSB0 19200 cs8 -cstopb -parenb -opost -inlcr
  stty -F /dev/ttyUSB0

  Send a File to Badge
  

  • On the badge, type sload into BASIC
  • On computer type: cat basic.txt > /dev/ttyUSB0
  • On the badge, press BRK

  Receive a File from Badge

  • On computer type: cat /dev/ttyUSB0 > newbasic.txt
  • On the badge, type ssave
  • On computer type CTRL-C

  MacOS X

  Be sure your adapter is properly installed and set up (may require downloading and installing driver) before using either of the two options below:...

  Read more »

• Guide for Programming in C

  Mike Szczys • 10/16/2018 at 16:21 • 6 comments

  Setting Up the Toolchain

  You will need a PIC programmer to write your own HEX files onto the badge. PICkit 3 and PICkit 4 have both been tested to work as programmers via the pin header on the badge.

  The BASIC badge is based around a PIC32MX370F512H. Software is compiled using MPLABX, XC32 compiler, and legacy peripheral libraries from Microchip.

  1. Download three packages:
     • Navigate to the Downloads" tab at the bottom of the Microchip Compilers page.
     • Download MPLAB® XC32/32++ Compiler v2.10 for your operating system
     • Download PIC32 Legacy Peripheral Libraries for your operating system
     • Navigate to the "Downloads" tab part way down the screen at the Microchip MPLAB X IDE page.
  2. Install the packages:
     • Install the XC32 compiler first
     • Install the peripheral libraries next. IMPORTANT: You must specify the same directory as the XC32 compiler. This will likely not be the default option during install. For Linux installation this director was: /opt/microchip/xc32/v2.10/
     • Install MPLABX IDE
  3. Open the MPLABX project from this repository
  • A PIC programmer like the PICKIT3 is required to program your badge
  • On the PIC programmer, pins 1-5 correspond to RES, V+, GND, B0, and B1 on the badge

  (If your programmer isn't recognized in Ubuntu 18.04 see troubleshooting below)

  Testing Your Toolchain Installation

  To test that the tools are properly installed before Supercon, clone the badge firmware repository on Github. Open the project, plug in your PICkit, and click "Make and Program Device"

  If all goes well, everything will work up to the point PICkit tries to communicate with a badge that's not there yet, at which time you'll see an error message like this:

  Target device was not found (could not detect target voltage VDD).
  You must connect to a target device to use PICkit 3.

  Congratulations! You are ready to hit the ground running. Once you pick up your badge and connect it to your PICkit, the firmware upload should succeed.

  User Examples for C Programming

  The stock firmware includes an example program that has both a menu entry, and many of the commands that will commonly be needed to write your own C code.

  • Selecting user program will run void user_program_init(void) first.
    • This is where you should do all of your program setup. This is a good function to call from your program when you want it to start over again.
  • After the init function is called, void user_program_loop(void) will be called
    • This is where the main functionality of your program should be stored.
    • If this function returns, it will immediately be called again.
  • millis() is a 32-bit upcounting millisecond timer. Non-blocking delays are a matter of setting a variable as millis()+1000 and then polling millis() until it is larger than this variable.

  Advanced

  • The screen defaults to scanning a 40x20 character array (screen will automatically update when array data changes). For direct control of the screen:
    • enable_display_scanning(0); //Turns off auto  screen scanning, value of 1 turns back on
    • view disp.h for screen manipulation functions to use in manual mode

  • When directly controlling the screen, you will want to perform a screen refresh after badge wakes up from sleep
    • There is function pointer in hw.h that will call your screen refresh function on wake. Here is the example for setting which function will be executed (do this in the initialization function of your program):
    • start_after_wake = &you_refresh_function;

  Troubleshooting

  Upon updating to Ubuntu 18.04 it seems that Microchip's...

  Read more »

• Hardware Hacking

  Mike Szczys • 10/16/2018 at 16:20 • 7 comments

  Front view of expansion Header:

  Here is a rear view diagram of the pin header taken from the badge schematic.
  

  These pins can be controlled from BASIC using the edir, ein, and eout commands. The UART on pins C13 and C14 can be accessed from BASIC using uin and uout commands. 

  G2 and G3 are 5V tolerant but all other pins should be interfaced at 3V.

  Important: there is no voltage regulation on the badge, and the PIC32 datasheet lists maximum Vdd of 3.6. Keep this in mind if upgrading power supply beyond a pair of AA batteries. (A fully charged lithium ion battery tops out at 4.2V.)

  Expansion Board

  New for the Hackaday Supercon is a hardware expansion board for prototyping your own circuits. Pictured here is the prototype. The final design will be black, and it will include three headers for #Shitty Add-Ons 

  To the right there will be a mounting hole so that the expansion board can be firmly affixed to your badge.

  Here is the front view (red) and rear view (green) of the circuitry for the expansion board. Here is the list of package footprints available:

  • 3 × Shitty Add-On headers
  • 1 × SO-8
  • 1 × SO-16
  • 1 × TSSOP-16
  • 2 × SOT-23 (for SMD transistors)
  • 14 × 0805 (for SMD passive components)
  • 1 × LGA-16 (for accelerometer only)

  All round pads are general purpose pads, and square ones are connected and intended for special use. The following drawing contains color marking for those pads, so the black pads are Ground (0V) connection, red pads are for +3V supply, green ones are I2C Clock pads, and blue ones are I2C Data pads. They are arranged so that you can use up to three shitty-add-on connectors without any modification of the PCB. 

  Pull-Up Resistor Footprints for I2C

  If you plan to use I2C (for your own circuit or for a shitty-add-on), pull-up resistors must be added. Please note that there are no pull-up resistors for the I2C bus on the main board, so you should add 4K7 (or similar) pull-up resistors on the noted 0805 footprints at the column "t", rows 4-5 and 6-7. Those 0805 footprints are marked as DA (data) and CK (clock).

  Adding an Accelerometer

  If you add an LIS3 accelerometer to your expansion board, it is highly recommended to add the ceramic capacitor at the column "q", rows 4-5. Its capacitance should be 4.7 to (preferably) 10 µF.

  Pin 1 of the accelerometer is at the bottom left. Only LIS3DH or LIS3DE accelerometers can be used, as the pads on the LGA-16 footprint are connected to required sources. Please note that LIS3DH and LIS3DE have the same pinout diagram, but they are many internal differences, including register and slave addresses. For instance, LIS3DH has 16-bit output reading for each axis, and LIS3DE has 8-bit outputs.

  Other Footprints on the Expansion Board

  There are 18 large square pads at the bottom layer of the PCB. All those pads are general purpose and are convenient for attaching large components or thick conductors.

  Leftmost and rightmost columns "A" and "v" can be used for SIL connectors. Holes on these pads are with 1mm diameter, so they can accept normal male pins of SIL headers.

• CP/M on Badge, Quick Guide

  Mike Szczys • 10/16/2018 at 16:20 • 12 comments

  After you start Z80 emulator with CP/M, the machine boots up on A drive greeting you by prompt

  A>

  There is not much to do with this drive, as it is 22kB RAM disk. It is empty after boot, as you can try with command

  dir

  that prints what is in current directory. You can switch to disk B, where is more to be found

  b:

  and system will respond with

  B>

  meaning you are there. You can now list content of this directory again and discover a few executable (.COM) files, like XMDM, MBASIC or FORTH. You can play around with those; notice that some of them expect different line (CR) end than what badge uses (LF). You can do CR line end by hitting SHIFT+ENTER. Exit MBASIC by typing system<CR>.

  On disk C you have some more goodies, namely famous ZORK game and SARGON chess game.

  Disk D is empty, with 512kB of capacity. You can copy files to/from disks utilizing PIP program, with syntax of

  pip d:=c:zork1.com

  that will copy file zork1.com to drive d. Notice you should run this one from disk B, where pip resides, or explicitly set path to pip program.
  

  If you want to erase the file, just type

  era d:zork1.com

  If you happen to need to list ASCII file, invoke command

  type file.txt

  or dump binary file in hexa form by running

  dump file.bin

  Stat command is used to display statistics of a file or drive; you can run
  

  b:stat
  

  to display info of drives or

  b:stat *.*
  

  to display information about all files on particular drive. Notice the wildcards - you can use it when copying or erasing the files too.

  If you want to transfer files from computer (or perhaps another badge), you may use XMODEM program. Run

  b:xmdm r d:filename

  to start saving received file on D drive, and start XMODEM transfer on other side. The transfer speed is 19200 baud. You may try to archive files into ARC format and un-arc it on CP/M side with dedicated software, if you want to transfer more files. On linux, you may want to use sx to transfer files, or moserial or cutecom for GUI access, with windows, teraterm is good option.
  

  You may want to try assembler toolchain consisting of ED editor, ASM assembler, LOAD program to convert hex to .COM file and DDT debugger. There is quite a lot of Z80 CP/M software on the interwebs, you may want to look for "walnut creek CP/M CD". Be prepared that a lot of CP/M software was designed for modified machines, sidetracking BIOS, so it may not run on this particular machine.

  Notice badge has option to switch from local standard input/output (keyboard/display) to serial port (on pins C13 and C14 on expansion port, 3,3V levels, don't forget ground) by pressing LSHIFT+RSHIFT+BRK; with the same combination taking you back to local access. You may access the command line using terminal emulator on your PC, gaining somehow more comfortable access.
  

  You can find more details about the CP/M commands and programs here and here.
  

• Tutorial for Programming in C

  Mike Szczys • 10/16/2018 at 16:19 • 3 comments

  Use your badge as a flashlight with 'lumos'

  This tutorial walks through the following:

  • Find out how to do something on the badge, by looking at implementation details of a related existing BASIC command.
  • Look at three ways to trigger the new code:
    1. Add it as a program to be launched at main menu command line.
    2. Add it as a new BASIC command.
    3. Add it to the default user program.

  One of the first things we do with the badge is to light up its LED using BASIC commands. For this tutorial, we want to light up all three LEDs to use the badge as a flashlight. We can do this with the following simple BASIC program:

  10 led 0,1
  20 led 1,1
  30 led 2,1

  This works, but it's silly to take up a BASIC program slot just for this. So in order to add this feature to badge firmware, we start by looking at what happens under the hood when BASIC sees the "led" keyword.

  • basic/tokenizer.h:
    • Declare enum TOKENIZER_LED.
  • basic/tokenizer.c:
    • Static array keywords[] associates command string 'led' with TOKENIZER_LED.
  • basic/ubasic.c:
    • Inside function statement() a TOKENIZER_LED triggers a call to led_statement()
    • led_statement() processes the tokens and calls into set_led()
  • hw.c:
    • set_led() sets the PIC32 pins corresponding to LEDs.

  Copying from set_led(), we can write a short function to turn on all three at once:

  void flashlight()
  {
    LED_R = 1;
    LED_G = 1;
    LED_B = 1;
  }

  Side note: this is equivalent to calling an existing function set_led_word(0x07), but for the sake of the tutorial we'll proceed with adding a new function.
  

  Now we'll survey the options for putting our new function to work, you can use any combination of the below as you see fit for your code:
  

  Option 1: add to main menu:

  To light up LEDs when user enters a command in the main menu, we edit badge_menu() in badge.c. After the user presses enter (NEWLINE), there's an if/else tree to process commands. We can add a new menu command to this list. We'll make our new command "lumos".

  [...existing code...]
      else if (strcmp(menu_buff,"lumos")==0)
          {
          flashlight();
          }
  [...existing code...]

  Now we can type "lumos" at the main menu to turn on flashlight mode.

  Option 2: add to BASIC commands

  (UPDATE: The Superconference badge firmware now has a much faster BASIC tokenizer, an upgrade over the Belgrade badge. The downside is that it's more difficult to modify. The instruction below applies to the slower but easier to modify BASIC tokenizer.)

  This retraces our steps digging into BASIC commands, this time adding our own code.

  • basic/tokenizer.h: 
    • Declare enum TOKENIZER_LUMOS.
  • basic/tokenizer.c:
    • Add to keywords[] array to associate string "lumos" with TOKENIZER_LUMOS.
  • basic/ubasic.c: 
    • Add to the switch statement inside statement(), so a TOKENIZER_LUMOS will call  lumos_statement()
    • Add new function lumos_statement() to process tokens and call flashlight().

  Now "lumos" will work as a badge BASIC keyword

  10 lumos

  Option 3: add to user program:

  The default user program waits for a user key press. Add a call to flashlight() just after a key is detected in user_program_loop() of user_program.c.

  [...]
      if (get_stat!=0)
          {
          flashlight(); /* Turn on all three LEDs */
          /* Show which letter was pressed just as an example: */
  [...]

  With this change, the LEDs will light up on the first key press after the user program starts.

  But the user program is your playground to do as you please,...

  Read more »

• C Programming HOWTO Reference

  Mike Szczys • 10/16/2018 at 16:19 • 0 comments

  This section is a concise reference guide for Superconference hackers short on time. It will continue growing through Supercon weekend to be a programming FAQ as needed.

  HOWTO: Get an overview of badge code

  • main.c: Most of this file is a large comment block describing overall project layout.

  HOWTO: Free up memory to make room for big projects.

  • badge_settings.h
    • Data memory: USE_RAM_IMAGE_NEW and USE_RAMDISK
    • Program memory: USE_ROMDISK and USE_ROMDISK2
  • Frees up memory at the cost of degrading/disabling badge's Z80 emulator running CP/M.

  HOWTO: Upload new badge firmware faster.

  • Free up program memory, see above. Smaller program memory means less data to transfer to the badge on every firmware upload.

  HOWTO: Manage memory at runtime.
  

  • The default badge firmware uses only compile-time memory allocation. (There is no call to malloc()) This avoids memory leaks, heap fragmentation, etc.
  • The following blocks of memory, allocated at compile time, may be available.
    • ram[]: 64 kb available when not running Z80 emulator. See splash.c for an example of how to use it.
      • Advanced challenge: code injection into Z80 emulator memory using ram[].
    • flash_buff[]: Available when not interacting with flash storage
    • bprog[]: Available when not running BASIC
    • disp_buffer[]  color_buffer[]: Available if not printing text on screen

  HOWTO: Draw a bitmap to screen.

  1. tft_set_write_area(x,y,width,height); //Set the drawing area
     1. IMPORTANT: Drawing area is INCLUSIVE. This means to draw the entire screen width of 320 pixels, "x" would be zero, and "width" is 319. NOT 320.
  2. TFT_24_7789_Write_Command(0x2C); // Begin bitmap data transfer.
  3. TFT_24_7789_Write_Data3(red, green, blue); // RGB value for one pixel, repeat until drawing area is filled.

  Example 1: disp.c: void tft_fill_area() fills an area with a single color.

  Example 2: nyancat.c: nyancat() renders animation frame line-by-line.
  

  HOWTO: Stop automatic redraw of text buffer on screen.
  

  • enable_display_scanning(0);

  HOWTO: Read/write nonvolatile (flash) memory.

  • hwz.c: fl_read_4k(), fl_erase_4k(), fl_write_4k()
  • badge_settings.h has a comment block laying out how flash memory is organized.
  • Example usage in badge.c: basic_load_program() and basic_save_program()

  HOWTO: Generate sounds which aren't musical notes.

  • hw.c: sound_set_generator()

  HOWTO: Read keyboard directly.

  • hw.c: keyb_tasks()
  • stdio_get() can get confused when multiple keys are pressed simultaneously so certain key combinations require direct reading. (Example: a game that needs to know a user pressed "Up" and "Right" simultaneously for a diagonal move.) 

  HOWTO: See under the hood of a BASIC command.

  • basic/ubasic.c: static void statement(void)
  • When the BASIC interpreter sees a recognized command (in the form of a token) statement() will call a corresponding C function to do the actual work.

  HOWTO: Add a new BASIC command.

  • tokenizer_generate/ubasic.re
  • This is the input file for re2c to generate a new high speed BASIC tokenizer.

  HOWTO: I2C
  

  (Added in version 1.21)

  • hw.c: iic_init(), iic_start(), etc
  • user_program_temp.c is not part of the badge firmware build, but serves as sample program demonstrating interaction with Si7020 temperature sensor over I2C.

  HOWTO: PWM

  • Easy way: Take over one of the three audio voice timers (Timer2/3/4) and, instead of always inverting one of the audio generator pins, count duty cycle and output to one of the expansion port pins accordingly.
    • hw.c: Timer2Handler(), etc.
  • Proper way: Use the PIC32 Output Compare peripheral to do basically the same thing, but using high performance dedicated hardware.

  HOWTO: Solve...

  Read more »

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