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Two parts of the project proved to be most challenging for us: (1) Initializing / logic for all of the inputs (2) Power distribution / management (3) Blue Tooth implementation of ESP32

(1) We initially struggled to find a balance between the different inputs and an "active low" logic system. Additionally, because we were working with an off-the-shelf app (Blynk) for our mobile device, it was difficult to debug when logic levels were not behaving the way we anticipated. For instance, when the app isn't driving a 1, is it actually driving a 0 or is the pin left floating?
We ultimately remedied this confusion by manually resetting logic levels when an input was not being read.

(2) We also had numerous problems with running the different power buses for the motor drivers and MCUs. Our first problem was a faulty AC/DC converter unit (brand new), that could not handle even a 3A load (rated for 5A) without shutting down. Second we had a faulty power management board that was supplying only 4.3V on the 5V output, and therefore our Atmega was getting faulty logic levels. We ended up finding both of these problems, locating a new 12V AC/DC converter, and building our own power distribution circuit. (got very hot!) Lesson, check all power resources before starting a project!

(3) As we had been warned, there were limited resources for the ESP32 bluetooth setup and use. After many hours, we reverted to using WiFi but ran into other mysterious problems with the ESP32. This is why we ultimately ended up using the Particle Photon, but we used the Arduino to run everything except the connectivity in case we ran in to further problems. AND by keeping the connectivity MCU separate from the main MCU we would keep the option of trying the bluetooth connectivity again later if we had time. We did not have time.