Like to use your arduino as an in-system programmer (ISP)?

Check out mega-isp on code.google.com

I have a handful of AVR chips that I'm using in various projects (including WOSP). You use the SPI interface to upload the software to the chip's flash memory. I wrote a custom program on the Arduino that would read in Intel S-records and push the program onto the chip. I hoped to simply send the programs a file at a time to the chip. Didn't work. There was no hardware handshaking between the USB Arduino and the computer, so it would fill the buffer and then hang. No fun. I tried adding xon-xoff control but couldn't get that working either. I could put the programs in using Hyperterminal, one line at a time. That got old before it was even new. I decided to clone the AVR910.

It wasn't hard to do, I just read through the published source from Atmel and converted it to C for the Arduino. Once I had it sending and receiving characters I got AVRDUDE and started debugging. I had some initial problems because I tried to tell avrdude I had an AVRISP. I didn't, I had AVR910. It took a few night's hacking but I got to where I could read and right EEPROM and Flash on the target chips. The last problem I fixed was a byte order thing with sending an address. Seems that avrdude sends the programs one byte at a time, preceeded by the address. So each time I would get the address but in the wrong byte order. I swapped it around and suddenly it worked.

My targets are ATtiny13, 15, and 2313. The tiny13 isn't officially supported by avr910, so I just assigned it an ID of 1 and it works. I haven't tried the tiny15 chip yet, but the programmer works for tiny13 and tiny2313.

So look for more AVR projects from me in the near future!

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...