Bought the 8 bit switch bank today ($4.80 for 10 switches), along with some 14 guage wire. Way overkill but whatever...

Sad 'cause sparkfun is down today. I'd like to get the ethernet breakout, and a few other things. I'll probably put in a Digikey order also, but getting the right parts from Digikey is a real chore. They have so much stuff! Looked for the octal buffers at RShack, no luck there. All they had was op-amps and 556 dual timers.

Still haven't decided if I will write the software for WOSP in C or ASM. Either would work fine. I'll try the switches out tonight. I'm sure the Arduino pinout diagram will come in handy.

Or, a new take on the Altair.

WOSP provides a way to create and edit programs in Atmel AVR microcontrollers at the byte level. The programmer provides a bank of 8 data switches for program input. Output consists of 12 address lines and 8 data lines. As the AVR uses word-based program memory the programmer shows one byte at a time, allowing you to switch between High and Low bytes.

The basic programming model is to set the switch bank, set the High/Low byte switch, then press the 'Write' key. Pressing the 'Up' button advances the address pointer to the next address. The 'Down' button allows movement backwards. Once the program is complete press the 'Store' button to send it to the microcontroller. You can also use the 'Load' button to read the microcontroller program into the editor.

A 'Goto' button allows you to enter a new address directly using the switch bank.

Implementation: The core of the WOS Programmer is an Arduino board running a simple program. The program defines a 512 byte data area for the target program. Input and output use 8 bit data latches and a common data bus (on the Arduino Port B).

There is also provision for uploading the target program from a host PC to save all the switch flipping.

When I plugged my Olimex 8pin AVR dev board into my Arduino I could read the device signatures just fine (after fixing one timing bug). But when I tried to write a program to the Tiny15 chip things got strange fast. Especially when I got the byte order wrong (started writing MSB into LSB - another bug). After that no matter how much I wrote the first few bytes of the program were always zero. No fun!

So I added a 'chip reset' to my programming software. This flips all the bits in the flash ON, after that it would take my program. Guess you can only turn the bits off when you program the flash.

For the Tiny15 program I wrote the code in Astudio4, then manually assembled it with -l tiny.lst. Then I openened tiny.lst and copied the machine codes into my programmer C code. The code would use the array to send individual bytes to the Tiny15 using SPI. OK, this is not a great way to do it, but it let me learn how the Tiny15 unit works.

I was disappointed that you could only set the bits OFF unless you reset the whole chip. That makes iterative development more difficult. I'm working on a 'way old school' programmer, which will allow you to enter the program 8 bits at a time (using 8 switches). The plan now is to capture the whole software image (or at least 256 words of it) in memory on the Arduino's ATMega8 chip, then erase and write it to the Tiny15 etc. I will also be able to read the Tiny15 program into the Mega8, edit it there, then push it back out to the Tiny15. More about the WOS programmer in my next post...