Tempe High School RP2040 Competition Robot

This project is a low-cost differential-drive robot platform built for students learning mechatronics and embedded programming. It combines practical robot assembly with staged MicroPython challenges, from basic wall-following PID to competition-style rescue behavior.

Quick Links

• Web Simulator: https://tempehs.github.io/AIDriver_MicroPython_Challanges/
• MicroPython Lab: https://lab-micropython.arduino.cc/

Build the Robot

Components

All parts are available from common suppliers (for example, AliExpress), with chassis parts made by laser cutting and 3D printing.

1. Laser-cut chassis file and 3 mm plywood
2. 3D-printed components (see manufacturing_files)
3. RP2040 Uno development board
4. Seeed Grove Base Shield V2.0 (UNO form factor)
5. 2x Seeed Grove Ultrasonic Ranger (front and side, default distance backend)
6. 2x VL53L0X ToF distance sensors (optional alternative distance backend)
7. Seeed Grove LSM6DS3 6-axis accelerometer + gyroscope
8. Omni wheel
9. L298N(H) motor shield
10. 4x Seeed Grove 4-pin cables
11. 2x TT tyres
12. 2x TT DC geared motors
13. 5.5x2.1 mm barrel jack
14. 6x AA battery holder with switch
15. 6x AA batteries

Note

This build uses Grove sensors on a Grove Base Shield. The default classroom path uses Grove ultrasonic sensors for front/side distance and an LSM6DS3 for closed-loop gyro turns.

Distance backend choice is simple: use 2x Ultrasonic sensors OR 2x ToF sensors.

Pin Assignments

Default GPIO map used by AIDriver (all pin numbers are RP2040 GP values).

Motors (L298N Shield)

Function	Pin
Right motor PWM/speed	GP3
Right motor direction	GP12
Right motor brake	GP9
Left motor PWM/speed	GP11
Left motor direction	GP13
Left motor brake	GP8

Distance Sensors (Choose One Backend: Ultrasonic OR ToF)

Mode	Front Sensor Pins	Side Sensor Pins	Notes
Ultrasonic (Grove default)	GP6 SIG	GP4 SIG	Single-wire Grove interface
ToF (VL53L0X)	GP29 SDA, GP28 SCL	GP6 SDA, GP5 SCL	Separate SoftI2C buses; both sensors use address 0x29

Note

In ToF mode, the front and side VL53L0X sensors are on separate SoftI2C buses, so both can use 0x29 without an address conflict.

The front ToF bus was moved from GP26/GP27 (Uno A0/A1) to GP28/GP29 (Uno A2/A3) because A0/A1 are physically wired to the Arduino Motor Shield's current-sensing outputs (see Pin Summary below). Bit-banging SoftI2C on those pins fought with the shield's analog current-sense lines and caused unreliable ToF readings. Do not reuse A0/A1 (GP26/GP27) for anything else — pick free pins instead.

Shared Sensors and Display (Both Modes)

Device	Interface	Pins	I2C Address
LSM6DS3 gyroscope	SoftI2C	SDA GP16, SCL GP17	0x6A
TCS34725 color sensor	SoftI2C + INT	SDA GP16, SCL GP17, INT GP7	0x29
SSD1306 OLED display	SoftI2C	SDA GP16, SCL GP17	0x3C
Rescue-kit servo (optional)	PWM	Unassigned by default	-

System Pins

Function	Pin
Firmware recovery/reset	GP2 -> GND during boot
Onboard status LED	GP25

Note

GP16 and GP17 form one shared bit-banged SoftI2C bus for the gyro (0x6A), color sensor (0x29), and OLED (0x3C). GP7 is used for the color sensor interrupt line.

Pin Summary (MicroPython GPIO ↔ Uno Header)

The controller board is an RP2040 chip on an Uno form-factor board, so every pin has both a MicroPython machine.Pin GPIO number and a silkscreened Uno header name (D0-D13, A0-A5). Dn maps directly to GPn. Only 4 GPIOs on the RP2040 are ADC-capable, so the Uno analog header only exposes 4 real analog pins: A0=GP26, A1=GP27, A2=GP28, A3=GP29. A4/A5 are not wired to RP2040 ADC pins.

The Arduino Motor Shield (L298N) is a fixed-function shield: it hardwires the pins below to its H-bridge and current-sense circuitry whether or not the code reads them. This table lists every pin the shield uses, including the A0/A1 current-sense lines that previously conflicted with the front ToF SoftI2C bus.

Uno Pin	GPIO	Motor Shield Function	Used By AIDriver
D3	GP3	PWM Channel A (speed)	Right motor speed
D8	GP8	Brake Channel B	Left motor brake
D9	GP9	Brake Channel A	Right motor brake
D11	GP11	PWM Channel B (speed)	Left motor speed
D12	GP12	Direction Channel A	Right motor direction
D13	GP13	Direction Channel B	Left motor direction
A0	GP26	Current sense Channel A	Free — do not reuse for I2C/SoftI2C
A1	GP27	Current sense Channel B	Free — do not reuse for I2C/SoftI2C

Warning

A0 (GP26) and A1 (GP27) are physically connected to the Motor Shield's analog current-sense outputs. Even though AIDriver never reads them, bit-banging SoftI2C (or anything else) on these two pins caused unreliable readings for the front ToF sensor. This is why the front ToF SoftI2C bus was moved to A2/A3 (GP28/GP29). Avoid A0/A1 for any new sensor wiring.

All other pins used by this project (Grove ultrasonic, ToF, IMU, color sensor, OLED, status LED, recovery pin) sit outside the Uno D0-D13/A0-A5 header and are only available via this board's extra GPIO breakout:

Function	GPIO	Uno Header Equivalent
Front ultrasonic SIG	GP6	D6
Front ultrasonic ECHO (legacy)	GP7	D7
Side ultrasonic SIG	GP4	D4
Side ultrasonic ECHO (legacy)	GP5	D5
Front ToF SoftI2C SDA	GP29	A3
Front ToF SoftI2C SCL	GP28	A2
Side ToF SoftI2C SDA	GP6	D6
Side ToF SoftI2C SCL	GP5	D5
IMU/color/OLED SoftI2C SDA	GP16	none (extra breakout)
IMU/color/OLED SoftI2C SCL	GP17	none (extra breakout)
Color sensor interrupt	GP7	D7
Firmware recovery/reset	GP2	D2
Onboard status LED	GP25	none (extra breakout)

Preparation

Note

TempeHS senior software engineering students may have already completed these steps.

Step 1	Step 2	Step 3
Cut VIN jumpers on the underside of the motor shield and verify with a multimeter.	Solder the battery pack leads to the barrel jack leads (red-red, black-black), then secure with a cable tie.	Fit the motor shield to headers, then build and flash custom MicroPython firmware with integrated AIDriver libraries.

Assembly and Hardware Testing

See Assembly_Instructions.md for full assembly and hardware test steps.

Build Custom Firmware

The build system produces firmware with AIDriver libraries frozen for fast import while keeping main.py on the device filesystem for easy IDE editing.

Quick build:

cd /workspaces/AIDriver_MicroPython_Challanges/.devcontainer
./build_firmware.sh

Recovery mode:

• If main.py is corrupted, hold GPIO2 low (connect GP2 to GND) during boot.
• Recovery restores default main.py and clears event_log.txt.

Full guide: Build_Custom_MicroPython_Firmware.md

Debugging and Event Logging

• Set aidriver.DEBUG_AIDRIVER = True in main.py for richer runtime logs.
• The firmware creates a run-scoped event_log.txt next to main.py.
• In recovery mode (GPIO2 held low at boot), both main.py and event_log.txt are reset to defaults.

Challenges

Students complete challenge stages in order, carrying code forward each time.

Stage 1: PID wall following

1. Challenge_1.md - P control
2. Challenge_2.md - PD control
3. Challenge_3.md - Full PID

Stage 2: State-machine maze solving

1. Challenge_4.md - Corner detection and first state machine
2. Challenge_5.md - Outside corners (nib state)
3. Challenge_6.md - Dead ends and nibs in one machine
4. Challenge_7.md - Full maze capstone

Stage 3: Rescue sensors and competition behavior

1. Challenge_8.md - Ground color detection
2. Challenge_9.md - No-go zones and recovery
3. Challenge_10.md - Competition run, victims, score, OLED

Use the web simulator to test before uploading to hardware: https://tempehs.github.io/AIDriver_MicroPython_Challanges/

Competition

• Rescue_Maze_Rules_Summary.md: plain-language guide to the RoboCup Junior Australia Rescue Maze rules.

Author

• @benpaddlejones

License

Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0).