I'm building a coin-flip device using the Atmel ATtiny15L. I bought a few way back when I got my Butterfly from Digikey. Anyway, I could program the chip just fine, but it wouldn't ever start running. I don't know what made me think of it, but I tied the reset line HIGH and it started working! I guess the 15L doesn't have an internal pullup on the /RESET line, so it was just floating. I didn't have this problem with the Tiny13 or Tiny2313 chips.

The coin-flip is fun. You push a button and the two LED's start flashing, then they slow down and stop on one: Green for heads, Red for Tails. It waits a bit, then shuts everything down. Push the button and it wakes up and does another flip. I'll have to check the current drain while it sleeps, but I think it will not be too much. I leave the counter running on the chip, I think it makes it more likely to seem random. I sample the lowest bit of the counter when you release the button, and the counter is fast enough that you have about a 50/50 chance of getting a one there. The rest of the flashing is just for show.

I'm planning to build this in permanent form over the weekend. Maybe I'll build a second one as a gift.

I've got this old RC car that I've been meaning to rebuild for years now. I just haven't been able to do anything with it. I was thinking about doing a line following robot, but the thing is just too darned fast for that to ever work. So I came up with a new concept today...

I'll just put an accelerometer on the thing. Forward motion: keep going. No forward motion: back up and turn. Yeah, it would be stupid. But fast. And probably destructive. Maybe I'll put it in the robot wars someday. If it can just keep going, maybe the opponent robot will self-destruct at some point. Perhaps I should add some extra weight, give it more impact when it hits something...

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!