Summer Hackathon: Conclusion

The Summer Hackathon I started on in May came to an end in August when I displayed a lot of what I had been working on at Makevention. I finished some projects and abandoned some others. Here is the outcome of the projects I set out to work on.

EEPROM Computer	Progress:	Abandoned
As I mentioned in the last update, a 4-bit version of this kind of computer has already been made by someone else. In the future I may make a 32-bit version, but for the time being I am done working on this.

8-bit Homebrew Computer	Progress:	20%
For this project, I designed a lot of the opcodes and most of how I want the computer to work. The chips I want to use don't seem to be simulated anywhere, so I will have to breadboard everything to test it out. So far I have one chip working just to test how it works.

Brainfuck Microcontroller	Progress:	55%
Apart from a few counters and status LEDs on a breadboard, I started soldering some boards with double row headers to hold everything.

Juggalo Robot	Progress:	70%
During the summer I didn't make much real progress on this project. I spent most of my time working on projects for Makevention instead.

ESP8266	Progress:	50%
I got an ESP8266 up and running. At first I had problems with the power supply but the chip seems to run alright with those problems solved. It also lists and connects to networks. Next, I need to connect to a server and transfer data, which will be used for a calculator project.

Wireless Breadboard	Progress:	Failed
This project was a failure. First of all I made a mistake with the spacing of the headers and it wouldn't fit the breadboard I was using. When I was working with it later I broke the entire header in half. The project wouldn't work anyway because the breadboard drops so much voltage. Unless I can find a breadboard that is much better, I don't intend to work on this project.

ATF1508 CPLD	Progress:	Done
After a lot of trouble and replacing a bricked chip, I eventually found a way to reliably program this chip. I also soldered a board to use for testing. This should be everything I need for the project I will use it in.

BASIC Interpreter	Progress:	30%
I also didn't make any progress on this project either. It would have been used with the Wireless Breadboard project if I had finished it. I will keep it for a later project I might need BASIC for.

LCD Programming	Progress:	50%
I got an LCD working for the 6502 Graphing Calculator project, as well as a VFD (technically not an LCD) for the Improved RPN Calculator. I did not get the LCD on the STM32F429 Discovery board working because I didn't need it for the Improved 6502 Trainer. I also haven't gotten the monochrome 5.5 inch LCD that requires -27v working yet. It will probably be easier to get a color LCD of that size instead.

Improved 6502 Trainer	Progress:	Done
I finished just about everything I wanted to for this project. It is much faster than the first 6502 Trainer. I will use it to develop for the 6502 Graphing Calculator.

Improved RPN Calculator	Progress:	95%
I finished almost everything for this project except a permanent keypad. I also renamed the project "Programmable RPN Calculator." The keystroke programming can repeat keystrokes, but it can't do any testing or branching. I will add those features eventually, but not in this version of the hardware. I shrank the size of numbers from 255 bytes down to 140. This lets me store all the temporary registers used during calculations on the chip, which makes calculations about five times faster. When I make a keypad I will be finished.

Summer Hackathon: Update

During the past few weeks I have had a lot of time to work on the projects I planned for my Summer Hackathon. So far I haven't made as much progress as I hoped, mostly because two of them took a lot more time to get going than I expected. Here is my what I have done so far on the ones I have worked on.

EEPROM Computer
Basing a computer architecture on precomputed lookup tables seemed like a an interesting idea when I started working on an assembler program for a 4-bit EEPROM-based computer. On IRC I explained what I was intending and the creator of the CADET computer showed me what he had accomplished. It is more or less the same thing I wanted to build, so I decided to stop work on this project for the time being. After discussing the idea with a friend at our hackerspace, I decided that it would only be worth continuing this project if I expanded it to a 16 or 32-bit architecture.

Brainfuck Microcontroller
For this project I have only hooked up four 74ALS193 counters since the last update. These will be the address counters for the program memory. My plan is to build the computer in small parts on a breadboard and transfer them to protoboard when I finish each piece. Rather than lay everything out on a a large board, I started soldering 8x12cm boards that will stack with double row headers. This way I will have plenty of pins to transfer signals between boards. I also plan to put LEDs on the topmost board to show signals like the address, jump buffer, op code, data pointer, and control signals.

ESP8266
A guy at our hackerspace was having trouble getting his ESP8266 going, so I set mine up to figure
out how to do it. Luckily for me, mine worked fairly well on the first try. The 03 variant I bought last year looked especially good since it is a little smaller than the others I looked at, and has several GPIOs, which I will need for one of the projects I have planned. One inconvenient thing is the 2mm pitch of the pins, which is slightly smaller than the 2.54mm, or 0.1'', pitch of a breadboard, but I soldered a small adapter. The firmware behavior is a little different than what some of the tutorials say to expect, but I was able to get a list of wireless networks at my house and connect to the WiFi at our hackerspace.
The LED of my friend's ESP8266 only lit dimly on my breadboard, as the voltage dropped down as low as 2.3v when run through the 3.3v LM1117 regulator I was running my repurposed 5v supply through. We haven't been able to figure out why this happens yet. For my chip the voltage also sank to about 3v, but it was still enough to keep the chip working. The supply itself seems to be good, as it delivers 5.18v, so I think the problem is with the regulator. When I tested the supply without the regulator on a breadboard with the 74ALS193 counters for the Brainfuck microcontroller, one side of the breadboard was down to 4.8v while the supply was still at 5.18v. Moving the jumper wires on the power rails around brought everything back to 5.18v

Wireless Breadboard
This project was especially exciting to me because it can be used to debug several of the other projects. To begin with I cut one of my 8x12cm protoboards in half and soldered single-row female headers to them, so a breadboard with male headers soldered on could be plugged into it. Unfortunately, I miscalculated the width of the breadboard and soldered the female headers on too wide apart. My local shop has been out of headers lately, so I tried to desolder the headers and broke a row of them in half in the process. So far I would consider this project a failure.

ATF1508 CPLD
This is an essential part of the 6502-based calculator I am hoping to build soon. Unfortunately, it has been my main source of headaches over the past few weeks. First of all, I tried to program the chip with an MSP430 generating JTAG signals from an svf file but this failed. After some searching, I found out that the JTAG standard is not really "standard" at all, and chips from different manufacturers handle the standard differently. Next, I tried generating a pcf file from the svf file, because it contains the actual states of every pin on every clock cycle. Although this worked and I could program the chip, the programming steps were ridiculously complicated. After using Atmel's WinCUPL program (which itself is rather unpleasant to use) to generate a JEDEC file, I convert it to an svf file with the Atmel ISP program. The problem with this is that the program offers a couple of nonsense error messages and just crashes if the FTDI cable I use to communicate with the MSP430 is still plugged in when I start the program or click the button to generate the svf file. Next, I have to switch to a virtual machine to generate the pcf file, since Atmel's SVF2PCF utility is 16-bit only.
After generating this, I have to replug my FTDI cable into USB and start a program I wrote myself to stream the PCF bytes to the MSP430. In an effort to streamline the process, I tried using Altera's SVF2PCF utility to generate the pcf file, since it is 32-bit, but unbelievably it leaves out all delay statements necessary for programming. When I tried transferring this file, the CPLD stopped responding and is now essentially bricked. For some incomprehensible reason the pins necessary for programming can be reassigned to other purposes, rendering the chip unprogrammable. At $14 apiece, this was an expensive error to make.
When my troubles with this chip started, I ordered a Byteblaster JTAG programmer, as the Atmel datasheets list this as a possibility for programming the chip. When it arrived, I quickly found out that the USB Byteblaster I had ordered has nothing at all to do with the Byteblaster cable that Atmel ISP can use. The open source driver I tried for the programmer caused my Windows 7 computer to crash with the blue sreen. Next, I ordered a USB to parallel converter cable, since the schematic for the Byteblaster is just a 74HC244 chip connected to the parallel port. So far I have not tried programming with this chip and may go back to programming with the pcf files generated by Atmel's 16-bit SVF2PCF utility.

Improved 6502 Virtual Trainer
In my post about GCC for the STM32F429 I explained how difficult it had been to get a GCC toolchain running. While I did get the toolchain to work in the end, I was unable to make any of the USB-to-serial examples work. This is very attractive for this project because I could use the chip as a Virtual Com Port and wouldn't need an FT232 chip or USB-to-serial cable. Many examples used the STM32CubeMx program from ST to generate the base code. None of the generated projects, however, can be opened with Eclipse, This is especially disappointing considering that the page for the utility lists GCC as a supported toolchain (although it is not actually in the list of toolchains in the project generator!) and provides an Eclipse plugin form of the utility. As I stated before, developing for STM32 with free tools has been a real pain! I tried the OpenSTM32 IDE, which is based on Eclipse and the libopencm3 library. This was able to compile a USB project generated by STM32CubeMx, but not without a good bit of fiddling with the files generated.
Next I soldered a small board for the 6502 that fits on the STM32 board. The pins of each port are not grouped together on the chip or on the headers on the board, but 8 of the 16 pins of port A are grouped together so I connected the 6502 data bus to them. Pins PA1 and PA2 only rose to 0.6v when driven high, which seems to be due to them being connected to some of the peripherals on the board. I connected PB1 and PB2 in those pins' place, so reading or writing the data bus means combining data from two different ports, but it does work. So far I have the chip working in single-cycle mode with the same software I made for the first trainer. My plan is to leave this software unchanged so it will work with either board.

Makevention
Our hackerspace is sponsoring a convention for makers in August and I would like to show some of my calculator projects there, so for the next two months I plan to focus mostly on the Improved 6502 Trainer and ATF1508 CPLD. These will both be necessary for the next calculator I want to build.