Ooh, that makes me think of the potential for swarms that leverage drafting for reducing collective energy expenditure when traveling together in formation.
Thinking out loud, maybe each bot could continuously monitor the motor’s energy draw when keeping pace as a proxy for wind resistance.
I tried to get the RGB LEDs working last night, but ran into a snag where the pi is not detecting any devices connected to the i2c bus…
iex(4)> Circuits.I2C.detect_devices()
Devices on I2C bus "i2c-1":
0 devices detected on 1 I2C buses
I’m expecting to see a device with address 0x54 based on what I’m seeing in the python library. Not sure how to proceed… but maybe I’ll just skip controlling those leds for now
This is probably a silly suggestion, but have you enabled the I2C communication on your R-Pi?
Apparently I cannot upload images…
Here you go - Enable I2C Interface on the Raspberry Pi - Raspberry Pi Spy
It’s a good questions. I’m using GitHub - nerves-project/nerves_system_rpi3a: Nerves system for the Raspberry Pi 3 Model A+ w/ gadget mode · GitHub as my base image and it has I2C enabled.
I think that’s why i see an i2c bus listed, but I don’t see any devices on that bus
The package was delivered this morning. Next up: assemble the parts. Didn’t expect that to be honest 
I’ve been on vacation this week and didn’t make much progress, but I did get a little battery case designed and printed, and wired up a pair of old 18650 battery cells from a head torch to work as batteries for the project.
This has been working well and keeps the bot pretty light compared to the battery bank that I had sitting around. I also worked a bit on the ultrasonic sensor, but didn’t get it working. I tried looking at the python code and it seemed to just send a pulse on an output GPIO (to power the ultrasonic speaker?) and then it waited for an input on an inbound GPIO (the receiver pushing a signal?), but after trying this with pullup, pulldown and floating input settings, I never get a reading back on my input pin: trilobot/lib/trilobot/sonic.ex at 3c3814f749848d67d909121f7cbd666ccc63623f · mmmries/trilobot · GitHub
So the motors, buttons and simple LEDs are all working great, but I haven’t been able to detect the RGB LED board via I2C and I can’t get the ultrasonic sensor working. I’m considering re-burning my SD card with just a raspbian install so I can try out the python code samples to see if it that works 
Just ordered mine. Yay for robots!
Re: The i2c not being detected - have you tried to communicate with the documented address anyway? I think it’s technically possible for the address not to show, but need to confirm.
We also prob need to confirm the frequency used for I2C vs what the device expects.
Booyah! When @jjcarstens jumps into the project you know it’s going to be real good!
I did try sending a few commands to the LED controller, but didn’t get anything to light up. I was also translating a lot of python code to elixir and I’m not sure I was actually assembling the right binary commands. I’ll try to find some documentation around the frequency used to see if that might be the problem too.
I found the datasheet for the I2C chip commited as part of the python library. sn3218/datasheets/sn3218-datasheet.pdf at master · pimoroni/sn3218 · GitHub
Looks like they are using a 400kHz clock frequency, but I couldn’t find what the default frequency is for the circuits_i2c library.
The datasheet doesn’t document the I2C commands, but I did find an arduino library which is looks like it has a pretty straightforward API that mimics the I2C interface pimoroni_arduino_sn3218/sn3218.cpp at master · pimoroni/pimoroni_arduino_sn3218 · GitHub
