Since the last blog (Applying Murphy) I did all my tricks and other people's tricks but none of them solved the servo jitter problem. What did work in the end was removing all I2C communications. After that my bot happily tracked me as I celebrated the return of some kind of functionality. After some careful consideration I was able to pile the 18M2+20X2 setup into one almost-maxed-out 20X2. Without the need to slave the 20X2 (paired with the problems I'm having), the attractiveness of two-wire I2C communication disappeared. I've just ordered an MCP23S08 with the SPI protocol to replace the PCF8574A and I2C all together. I had not yet used the option of using the A.0 pin for both SERIN and another I/O duty so it works out perfect. And I found a sweet ultra-mini-rocker DPDT for the switch :D
I feel satisfied now that I'm using just one 20X2 and it's 100% utilized. I have a good feeling about this new config as I've seen serveral "I2C servo wtf" type of posts but no SPI versions on the same subject. Grr PICAXE (sometimes...)
I'm going to be away from My Box for a stretch, enough to potentially give me withdrawls, but the bot really has to be put on pause again. I seemed to have fried my MP3 module so I had to order a replacement. I also found the h-bridge chips I'd selected for motor drivers would only work from 8-40V. I have 7.2V. :bang head here: So I ordered a couple L298HN's that have a nice low-profile package.
Including the I/O expander I just purchased, all these bits will take some time to get here so I can vacation easy knowing I'm stuck in the mud, robotically speaking. I'm hoping to test out running the processor at 16MHz and maybe even 32MHz before I go. I worked out a nice round timer3 vs seconds value at 16MHz and I hope to find the right formula for 32MHz. The standard 8MHz is way too slow; there's no need for any pauses after SERVO commands and it's still very shakey. This is while running a skeleton tracking-only code. The real McCoy will have almost 4X as many lines. We need to crank up the warp drive, Scotty! It should work Jim-dandy. Hmm... how to work Spock into this monologue... bah :)
Included a video for historical posterity. If I die in a plane crash, know I was ready, I want all my electronic stuff to go to LMR for challenge prizes, and I love you all lol What a will and testament. Aloha, LMR!
https://www.youtube.com/watch?v=bqwqHOSzlMk