Reference Design SparkFun XRP

Reference Design: SparkFun XRP Robot Kit (RP2350B)

Overview · What you need · Firmware · Hardware · Wiring · Setup · Status

_{SparkFun XRP Controller. Photo: SparkFun Electronics, from SparkFun_XRP_Controller, CC BY-SA 4.0.}

Config	xrp_config.yaml
Drivetrain	2WD differential (the kit's own chassis); 4WD skid steer or mecanum with ports 3 and 4
MCU	RP2350B on the XRP Controller (48 GPIO, 16 MB flash, 8 MB PSRAM)
Firmware image	pico2-jazzy / pico2-lyrical (the Pico 2 W release) plus the XRP env block
micro-ROS link	USB serial (/dev/ttyACM0)
LiDAR	LD19 on the robot computer's USB (/dev/ttyUSB0, 230400 baud)
Status	⬜ flashed on a real XRP Controller: topics and the LSM6DSOX check pass; motors not yet driven

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Overview

SparkFun's XRP Controller on the XRP kit's 2WD chassis, with the kit's two encoder gearmotors and its 4 × AA pack. It is a complete commercial robot, so it carries the kit's own wheels, motors and weight rather than the shared default chassis. Its Nav2 speed limits are the ones drivetrain_report.py derives for those motors.

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What you need

Part	Notes
SparkFun XRP kit (the "Beta" or the current RP2350B kit)	Controller, chassis, two encoder gearmotors, wheels, battery holder
4 × AA batteries	Into the kit's holder and barrel jack
LD19 LiDAR + its USB adapter	Into the robot computer, mounted on the kit's top plate
Robot computer	A Raspberry Pi 5 or any arm64/x86 computer running the cockpit (Installation & Docker). On the small XRP chassis it usually rides on a deck above the kit
USB-C cable	XRP Controller to the robot computer

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Firmware: the Pico 2 W image with an XRP env block

The XRP has no image of its own. It runs the RP2350 release, pico2-jazzy or pico2-lyrical, the same image as a Pico 2 and a Pico 2 W. That image numbers all 48 GPIO of the RP2350B, and the cockpit writes the XRP's own wiring into its env block when it flashes:

Env key	XRP value	What it does
cyw43_pins	26,29,28,27	The RM2 radio's REG_ON, DATA, CLOCK and CS, set before the radio starts
i2c_sda / i2c_scl	38 / 39	The IMU's bus: an I2C1 pair, so the firmware runs Wire on I2C1
battery_pin	46	The VIN divider, on ADC6

Applying the design does the rest: the cockpit downloads pico2-<distro>, flashes it with picotool, and writes this env.

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Key Hardware Specifications

Component	Specification	Notes
MCU	RP2350B (dual Cortex-M33, 150 MHz)	48 GPIO; 16 MB flash, 8 MB PSRAM
Radio	Raspberry Pi RM2 (CYW43439) on GP26–29	Off: an RP2 runs micro-ROS over USB serial, and Wi-Fi (with syslog and OTA) belongs to the ESP32's Wi-Fi transport. Pins from cyw43_pins
Motor drivers	On-board TI DRV8411A	Two PWM inputs per motor, no enable (pwm: -1)
Encoders	Kit gearmotors	585 counts per wheel revolution
IMU	ST LSM6DSOX (6-axis)	I2C1; 0x6B with the ADR jumper (JP4) closed as shipped, 0x6A open
Battery sense	VIN → 100 kΩ (R22) / 33 kΩ (R23) → GP46	ADC6; 13.3 V full scale
USB	SparkFun firmware 1b4f:0046; Pico 2 W image 2e8a:f00f; BOOTSEL 2e8a:000f	Detected by the cockpit as an RP2350

Kinematics & Nav2 limits

Setting	Value
Base	2WD differential
Wheel diameter / track	60 mm / 155 mm
Motor	140 rpm at 4.5 V, 0.75 A stall
Robot mass	0.8 kg
Path speed (desired_linear_vel)	0.16 m/s
Velocity smoother ceiling	0.19 m/s, 1.32 rad/s

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Wiring

Function	GPIO	Notes
Motor 1 (left) IN A / IN B	35 / 34	DRV8411A, port L; forward drives IN1 (GP34)
Motor 2 (right) IN A / IN B	32 / 33	DRV8411A, port R; forward drives IN2 (GP33)
Encoder 1 (left) A / B	30 / 31	invert: true: the left encoder is mounted mirrored
Encoder 2 (right) A / B	24 / 25
Motor 3 (rear-left) IN A / IN B	21 / 20	Port 3 (IN1 GP20, IN2 GP21), wired mirrored like port L; -1 on the 2WD kit
Motor 4 (rear-right) IN A / IN B	10 / 11	Port 4 (IN1 GP10, IN2 GP11), like port R; -1 on the 2WD kit
Encoder 3 (rear-left) A / B	22 / 23	invert: true if mounted mirrored like the left; -1 on the 2WD kit
Encoder 4 (rear-right) A / B	2 / 3	-1 on the 2WD kit
Motor current sense (ADC)	40 / 43 / 41 / 42	Ports L / R / 3 / 4; not used by the base
I2C1 SDA / SCL	38 / 39	On-board LSM6DSOX and the Qwiic port J13
Battery sense (ADC)	46	100k / 33k divider
Sonar trigger / echo	0 / 1	The kit's HC-SR04 header; also a Nav2 collision-monitor source
Status LED	64	On the RM2 radio
Wi-Fi radio	26–29	Reserved; the pin check rejects them

Everything is on the controller: plug the left motor's 6-pin cable into Motor L and the right one into Motor R, and the battery into the barrel jack.

For a 4WD skid steer or mecanum chassis, set the drivetrain on the Base tab and fill in the motor 3 and 4 rows above. Plug the rear-left motor into port 3 and the rear-right into port 4, following the wheel order. Every encoder pair has B = A + 1, which the RP2350's PIO quadrature reader needs. Set the rear motors' inversion from the tool's motor (its DIR WRONG flag), not from this table.

Note

The pin map agrees across SparkFun's KiCad PCB, the pico-sdk board header, MicroPython's SPARKFUN_XRP_CONTROLLER pins, arduino-pico's sparkfun_xrp_controller variant and XRPLib. The motor and encoder directions are confirmed by the drive suite the first time a kit is flashed; the 4WD rows have not run on hardware.

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Setup, step by step

1. Install the cockpit on the robot computer: Installation & Docker.
2. Plug in the XRP Controller by USB-C, battery off. Out of the box it runs SparkFun's MicroPython firmware (1b4f:0046); the cockpit still recognises the RP2350.
3. Name your robot and apply the kit. Type a name for your robot in the header's Robot field and press Enter, then pick SparkFun XRP Kit -- XRP Controller (RP2350B + RM2), 2WD, LSM6DSOX under Reference Designs on MCU & Sim (tab 1). A kit brings its own motors, wheels and chassis with the board; if yours differ, change them on Base (tab 2) and Drive & Motors (tab 3). Your robot is real from then on: no simulated devices, and every change you make is saved to it as you go.
4. Flash: press Flash MCU on Hardware Tests (tab 6, Firmware image). The first flash installs pico2-<distro> and the XRP env; then Enter tool and Sensors: the tool lists the LSM6DSOX on I2C1. If the flasher reports that the board did not enter BOOTSEL (SparkFun's MicroPython does not answer the usual 1200-baud reset), either run import machine; machine.bootloader() in its REPL, or hold BOOT, tap RESET and release; then flash again. Once our firmware is on it, later flashes need neither.
5. Motors: turn the battery switch on, lift the robot, run motors in the tool. The left wheel (MOTOR 1) then the right must go forward in FWD with a positive RPM.
6. Battery: sensors prints BAT: from the VIN divider; compare it with a multimeter.
7. LiDAR: mount the LD19 on the top plate with its zero facing forward, enter its position on Base (tab 2), and check it on LiDAR / Scan (tab 7).
8. First drive: (the design made the robot real: the header's badge reads 🔧 Real) leave the tool with Back to robot (base) so the board runs the robot firmware, start Bringup (tab 8) and drive gently with Teleop (tab 9). The kit is slow by design: 0.19 m/s at most.
9. Speed check: run the speed check against the LiDAR and put its ratios into the config before the first Nav2 goal.
10. SLAM and Nav2: on Operations (tab 11) press ▶ Start 1-Click Pipeline (the robot runs real).

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Status

Flashed on a real XRP Controller: the Pico 2 W release image with the XRP env publishes /odom at about 49 Hz and /imu/data at 50 Hz, and the tool's sensors finds the LSM6DSOX and reads gravity. The image, the env block and the pin map are checked against SparkFun's sources, and the Pico 2 W image passes the bench matrix in simulation mode. Not yet run: the motors, the LiDAR and a Nav2 goal.

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All reference designs · Pin Matrix & Wiring · Building a Real Robot