Firmware

The firmware running on the ESP32 microcontroller is contained in the vango-firmware directory. The firmware is responsible for establishing Bluetooth Low-Energy (BLE) communications, reading encoders, computing wheel angles and speeds,and computing the robot's pose through wheel odometry.

Communication

The VanGo robot is controlled via a BLE server. Using the esp32-nimble crate with esp-idf-hal, several BLE characteristics are established. For those unfamiliar with BLE, a characteristic is simply a part of the server that a client can read/write data to. Each characteristic is given a unique UUID to identify it by.

Below are the BLE characteristics provided by the robot and some information about what they are for.

Left/Right Speed Characteristics (Read | Write):

• Read: When read from, returns the current wheel speed
• Write: When written to, sets the target wheel speed to the written value

Pose X, Y, and \(\theta\) Characteristics (Read | Write):

• Read: When read from, returns the current x,y, or \(\theta\) position of the robot
• Write: When '0' is written to these characteristics, the value is zeroed

Pen Characteristic (WRITE):

• Write: When '1' is written, raises the pen, when '0' is written, lowers the pen