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• All quiet at eMBee HQ!

  Matthew Begg • 03/22/2021 at 09:45 • 0 comments

  Hi all,

  Just a quick update as you haven't heard from me in a while. Since the last update, I have started to move the project to a single veroboard/stripboard design, still using an Arduino Nano module, CardKB keyboard, 24LC256 EEPROM etc. But because I've changed my mind so much in the past, I've ended up struggling to desolder various pins and wires from each module (particularly the 1.54 inch OLED and the Adafruit PowerBoost). So I thought to make it easier, I'd order another screen. Which made me debate going back to the 'big' 2.42 inch OLED or stick with the 1.54 inch. You'll remember that my previous 2.42 inch display kept dimming at random intervals. But I'm assured that isn't expected behaviour and it must've been a faulty unit. So I have reluctantly ordered another 2.42 inch display from eBay. Will take about a month to come, so not much will happen with the project until it arrives. But then it should be full steam ahead with a new final unit being prepared, and the 3D printed parts being designed. Exciting!

  Previous comments on this project have included suggestions of various features to be added, which go beyond my original vision. Let me know in the comments below if you think I've got the balance right between simplicity, nostalgia and features.

• The first prototype!

  Matthew Begg • 02/19/2021 at 10:35 • 0 comments

  Hello world!

  
  

  Here is the first prototype of the eMBee ONE. Hand soldered, self-contained, and running from 2 x AAA rechargeable batteries. More pictures:

  A few things to note:

  • The screen is not where I wanted it to be. The idea was to have it centrally in the top lid, but I accidentally cut the ribbon cable too short, so it wouldn't reach.
  • Two switches to the right of the screen: 'PWR' connects the 'EN' and 'GND' of the Adafruit PowerBoost to act as a main power switch. 'BUZ' is to switch the buzzer off/on.
  • Fitting all those separate modules and prototyping boards into the bottom case is a tight squeeze. Future versions will definitely have the modules all on one prototyping board to make it thinner. 
  • The lid doesn't close. Partly because the screen is too far left and hits the CardKB GROVE connector, and partly because the modules are all separate and are too tall.
  • When typing, the keyboard bends in certain places as it isn't supported underneath.
  • The eagle-eyed among you will spot I forgot one connection - the VCC for the external EEPROM, so it currently can't access the 32KB of storage. However it's just a simple wire for that to work.

  Demo program

  
  

  Conclusion

  Really pleased with this first prototype - it just about proves the concept works. And, as with all good prototypes, it shows me what needs to happen next:

  • Use a custom-sized piece of prototyping board and attach the Nano, PowerBoost, EEPROM and buzzer to it. A single board will help with the space in the bottom half.
  • Use a longer ribbon cable for the display so it can be placed centrally.
  • The lid should close.
  • Once the second prototype is working, my cousin can provide the 3D printed bezel for the top, and perhaps a 3D printed support structure to stop the keyboard bending while typing.

  Let me know what you think in the comments below!

• Project update

  Matthew Begg • 02/09/2021 at 14:03 • 0 comments

  Prototype coming soon
  

  So I'm pretty close to having a rough prototype working. This will use an Arduino Nano, PowerBoost 500 Basic, CardKB keyboard, SPI OLED screen, piezo buzzer and 2xAAA batteries. Hoping to get that all soldered together and working in the tin this week. My idea of using mini breadboards isn't feasible due to the size constraints of the Altoids tin.

  That then begs the question: do I encourage people to build the same thing from all those modules? Or do I create a custom PCB using an ATMega 328P chip and make a single-board version to replace the Nano and PowerBoost? 

  3D printed bezel
  

  My cousin has very kindly offered to design and build a 3D printed bezel to mount the OLED screen nicely in the top of the tin. Once finalised, we will make the files for that available here.

  Comments
  

  Thanks to everyone who has commented so far in the discussion section below. Lots of nice comments and suggestions. Some people seem to want this computer to do more. For that, I'd recommend searching hackaday.io for 'pocket computer' as there are lots of much more capable computers with SD card support, networking, better screens etc. But that's not what I'm going for here. I want a text-based 8 bit system that runs BASIC for a minimal cost. No frills. Maybe the frills will come with the eMBee TWO ;-) 

  Another commenter suggested I build my own keyboard. That's a possibility in the future (especially to make it feel nicer than the hard feel of the CardKB keyboard) 

• Games to play on your eMBee ONE

  Matthew Begg • 02/04/2021 at 16:02 • 0 comments

  Once the eMBee ONE is released, you'll want to have some games to play on it. Despite only having a text-based display and 1KB of program memory, I think you'll be able to code quite sophisticated action games thanks to the 'POS' and 'INKEY$' commands. They allow you to position a character anywhere on the screen and take quick keyboard inputs. 

  Alternatively, lots of the printed listings in old Usborne 1980s computer books should work with minimal adjustments. And the listings in the seminal 1978 book 'BASIC Computer Games: Microcomputer Edition' should also work.

• Benchmarking the eMBee ONE

  Matthew Begg • 02/02/2021 at 15:30 • 1 comment

  I'm interested to see how the eMBee ONE compares performance-wise with the classic 8-bit computers from the 80s. I did a quick bit of Googling to find out the best way to benchmark old 8-bit computers, and found two interesting methods:

  The 'N-queen' chess problem - website

    10  CLEAR         
    20  R=8: X=0: S=0                     
    30  DIM A(R)             
    40  IF X=R THEN GOTO 180         
    50  X=X+1
    60  A(X)=R
    70  S=S+1
    80  Y=X
    90  Y=Y-1
   100  IF Y=0 THEN GOTO 40
   110  T=A(X)-A(Y)
   120  IF T=0 THEN GOTO 140
   130  IF X-Y<>ABS(T) THEN GOTO 90
   140  A(X)=A(X)-1
   150  IF A(X)<>0 THEN GOTO 70       
   160  X=X-1
   170  IF X<>0 THEN GOTO 140        
   180  PRINT S

  This doesn't seem to use up too much memory as it was originally used to compare programmable calculators. Even my old CASIO FX-730P (an inspiration for this project) is listed with a completion time of 7 mins 0 secs. However it uses the 'ABS' command which isn't supported in ArduinoBASIC. So first things first, I had to implement ABS in eMBee BASIC. This is my first attempt at adding to the list of commands. 

  Once that was done, I just typed in the code above, and typed RUN with a stopwatch ready. Would it beat 7 minutes for the FX-730P calculator?

  Er....yes. Result: 7 seconds! To be fair, the processor runs at 16MHz though, and this is a very efficient BASIC interpreter. But I wish I could tell my 13-year-old self that I've built a pocket computer that's 60 times faster than his!

  Prime Sieve benchmark - website

  10 W=500: DIM F(W): P=1: A=3
  20 F(P)=A: P=P+1: IF P>W THEN STOP
  30 A=A+2: X=1
  40 S=A/F(X):IF S=INT(S) THEN GOTO 30
  50 X=X+1:IF X<P AND F(X)*F(X)<=A THEN GOTO 40
  60 GOTO 20
  

  Simpler code that in theory would run on ArduinoBASIC, but results in a '10-Out of memory' error due to trying to create an array of 500 numbers in the first line! Time to beat here would have been 6 mins 28 seconds for the ZX Spectrum.

• OLED screen swap and adding external EEPROM

  Matthew Begg • 02/02/2021 at 10:20 • 0 comments

  I've now got a fully working prototype of the eMBee ONE! It is running on breadboards with the following components:

  • Arduino Nano clone
  • 1.54 inch OLED display connected via SPI
  • CardKB keyboard connected via I2C
  • 24LC256 external EEPROM connected via I2C (32KB storage)
  • Piezo buzzer (with 100 ohm resistor) to pin 5

  The new display doesn't have the dimming bug that the previous one did, and everything seems to working well. I came across a weird bug when loading programs from the external EEPROM though. I get a 'Bad parameter' error even though it successfully loads the program. Looking at the original ArduinoBASIC code, there's a missing 'return true;' statement at the end of the routine for loading so next time I'll try adding that and see if the error disappears.

  Next steps
  

  Now that I've discovered that the mini breadboards are thicker than I remembered, I think I'm going back to hard soldering everything together to keep things thin. Still might be able to get one mini breadboard in the bottom part of the tin, which gives some possibility for future expansion though...

  Currently I'm powering the whole thing via Mini USB, but hopefully I'll have the Adafruit PowerBoost 500 Basic arriving in the next few days so will be able to get it running from 2 x AAA batteries and make it a true pocket computer.

  Keyboard
  

  Love the form factor of the CardKB, but the reality of typing on it for more than ten seconds is pretty rough. Very hard tactile switches that leave imprints in your fingertips! So need to explore the possibilities of either adding some kind of membrane or set of keycaps? Or even build a keyboard from scratch using mouse buttons (thanks to Oscarv for that tip!)?

  'Pocket computer' or 'palmtop'?
  

  What should I refer to this as? I first came across the term 'palmtop' when the legendary Atari Portfolio was released. That was much bigger than this though. I want to go with whichever term suggests the smallest form factor, 'pocket' or 'palm'? Let's hear your thoughts in the comments below.

• The inspiration for this project

  Matthew Begg • 02/01/2021 at 15:46 • 0 comments

  Here is my original CASIO FX-730P pocket computer from back in the day!

  Still works!

  I can see there are 5 programs already on there with 5,247 bytes of storage free. Program 9 is the classic Horse Race game which I must’ve typed in from the original Casio manual. Place your bets!

• Fritzing diagram

  Matthew Begg • 02/01/2021 at 15:31 • 0 comments

  Here's the current setup that's working

• Future plans

  Matthew Begg • 02/01/2021 at 14:21 • 0 comments

  Don't want to get ahead of myself considering the eMBee ONE isn't even working yet, but thought I'd keep a log of ideas for future plans:

  
  Hardware

  • Adafruit RFM69 radio transceivers so that eMBee ONEs can communicate with each other

  Software

  • BEEP command (so you can easily do stuff with the buzzer on pin 5)
  • CHR$ support
  • User defined graphics? Change character sets to make text-based games more interesting

• Getting the hang of GitHub

  Matthew Begg • 02/01/2021 at 07:54 • 0 comments

  Rather than keeping the altered Arduino BASIC code to myself, I’ve officially forked the original code and will now maintain my version on GitHub. This is my first proper foray into using the service and I’m impressed so far. 

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