Electronics and firmware

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The robots board files can can be found on the GitHub project, current revision is rev2. This board is also the base support frame for the robots.

Please, note that this section is only relevant for people wanting to build their own kit from scratch, or to dig further in the design details. If you have a kit and want to program the robots using Python, you can skip this part.

Links

• Schematics
• Components (full BOM)
• Gerber files
• Eagle files
• Firmware sources

Firmware

Robot’s firmware can be found in the firmware/ directory of the GitHub repository.

You first need to install PlatformIO, that is used to bring you the full build chain, along with the tools required to flash the robot. Simply run:

pio run

In the firmware/ directory to start the build. And:

pio run -t upload

To start uploading your firmware on the robot (via USB).

You might want to check the src/config.h file to configure the firmware according to your hardware.

Commented design

ESP32 & Bluetooth

Robots are based on ESP32-WROOM-32E-N8 micro-controller, featuring 270Mhz dual-core with 32bit registers, integrated Bluetooth and WiFi controller.

An USB to UART adapter is used (namely FT232RL-REEL) to allow direct USB communication for the robot, making it possible to flash the on-board firmware without additional hardware. An USB type B connector was chosen because it is robust (in the case you want to do some tests with the robot on the floor and the USB cable plugged).

USB connection is only useful to flash the robot. In a normal pedagogical sequence, there is no need fo USB at all, since the programming for the robots behaviours actually happens in the PC controlling them by Bluetooth.

Power

Robots are designed to be powered by a 2-cells lithium ion battery, through the on-board Jack 2.35mm barrel connector. To avoid short-circuits or battery under-discharge, the board features a S-8252AAL-M6T1U battery protection IC.

When the battery voltage drops too low, the robot will first blink red and start beeping (which is the behaviour from its firmware), and eventually the BMS will cut the power.

In case of shortcut, the BMS will cut the power as well, you’ll have to turn the robot off and on again to get it restarting.

Buzzer

The buzzer is controlled by the micro-controller through an NPN transistor:

Leds

The board features 6 RGB LEDs (3 on the top and 3 on the bottom) that can be controlled individually. They are sold under the name COM-16346 or WS2812B.

Only one wire is necessary to control them all. The FastLED library is used for that purpose.

H bridges

Robots features TB67H450FNG,EL all-in-one motor drivers. Those IC come with integrated mosfets, mosfet drivers and current limiting features offering another protection against short-circuits.

Booster (Kicker)

To kick, the voltage is elevated to 20V using a MT3608 step-up converter. Two 25V 2200µF are then loaded, through a 270 ohm resistor to limit the current rush.

The kick consist in releasing all the current in a solenoid through a power