RTk.GPIO — USB GPIO for PC/Mac/Linux

A Python GPIO module that works on any platform. Plug in an RTk.GPIO board via USB and control 28 GPIO pins from Python — same API as RPi.GPIO. Supports PWM, pull-up/down, hardware SPI, and APA102 LEDs.

Based on anyio by David Whale (@whaleygeek), adapted for RTk.GPIO by Ryan Walmsley (@Ryanteck).

Firmware v2.2 — custom compiled, PWM via raw TIM3 registers, dual v1/v2 auto-detect.

Hardware

Parameter	Value
MCU	STM32F030C8T6 (Cortex-M0, 48MHz, 64KB flash)
USB	CH340G serial converter
GPIO	28 pins (GP0–GP27)
Baud	230400
PWM	6 pins via TIM3 (GP8, GP9, GP10, GP18, GP25, GP26)
SPI	Hardware SPI (GP9=MISO, GP10=MOSI, GP11=SCK)
Crystal	12 MHz HSE (firmware uses HSI fallback)

Quick Start

pip install pyserial

importsys; sys.path.insert(0, 'RTk.GPIO')
importanyio.GPIOasGPIOGPIO.setmode(GPIO.BCM)
# Digital I/OGPIO.setup(4, GPIO.OUT)
GPIO.output(4, True)
GPIO.setup(5, GPIO.IN)
print(GPIO.input(5))
# Pull-up/downGPIO.pull(8, GPIO.PULL_UP)
# PWM — tone generation, LED dimmingGPIO.pwm_start(9, 1000) # 1 kHz on GP9GPIO.pwm_duty(9, 128) # 50% dutyGPIO.tone(9, 440, 1.0) # A4 note, 1 secondGPIO.pwm_stop(9)
# Hardware SPIGPIO.spi_transfer(0xA5) # send byte, get response# Infoprint(GPIO.version()) # 'RTk.GPIO v2.2 2026-04-07'print(GPIO.is_enhanced()) # TrueGPIO.cleanup()

Auto-detect: single USB serial device found automatically. Multiple devices → interactive prompt. Port cached in portscan.cache.

API Reference

GPIO (RPi.GPIO compatible)

GPIO.setmode(GPIO.BCM) # required (no-op, for compatibility)GPIO.setup(pin, GPIO.OUT) # output modeGPIO.setup(pin, GPIO.IN) # input modeGPIO.output(pin, True/False) # write HIGH/LOWval=GPIO.input(pin) # read (True/False)GPIO.pull(pin, GPIO.PULL_UP) # pull-up (also PULL_DOWN, PULL_NONE)GPIO.cleanup() # release all, close port

PWM

GPIO.pwm_start(pin, freq_hz) # start PWM, 50% duty (20–65535 Hz)GPIO.pwm_duty(pin, duty) # set duty: 0–255 (int) or 0.0–1.0 (float)GPIO.pwm_stop(pin) # stop PWM, return to GPIO modeGPIO.tone(pin, freq, duration) # play tone, auto-stop after duration (sec)

PWM pins (TIM3): GP8, GP9, GP10, GP18, GP25, GP26

SPI / Info

GPIO.spi_transfer(byte) # HW SPI transfer, returns received byteGPIO.version() # firmware version stringGPIO.reset() # soft reset all pins → TrueGPIO.is_enhanced() # True if v2+ firmware detected

Serial Protocol

Pin char = chr(pin + ord('a')): GP0=a, GP27=|. Commands:

Command	Format	Response	Description
Input	eI	—	GP4 input mode
Output	eO	—	GP4 output mode
Write	e1 / e0	—	GP4 HIGH / LOW
Read	e?	e1\r\n	read GP4
Pull	eU/eD/eN	—	pull up/down/none
PWM	jW01F4	K or E	GP9 PWM at 500Hz
PWM duty	jP80	—	GP9 duty 50% (0x80)
PWM stop	jX	—	stop PWM on GP9
SPI	~A5	XX	transfer 0xA5
Version	V	RTk.GPIO v2.2...\r\n	firmware version
Reset	R	OK	soft reset all

Pin Map

GP0 =PA1 GP7 =PF1 GP14=PA2 GP21=PB10
GP1 =PB12 GP8 =PB5* GP15=PA3 GP22=PA11
GP2 =PB7 GP9 =PA6* GP16=PB8 GP23=PB2
GP3 =PB6 GP10=PA7* GP17=PB15 GP24=PB3
GP4 =PA8 GP11=PA5 GP18=PB1* GP25=PB4*
GP5 =PA12 GP12=PF0 GP19=PA15 GP26=PB0*
GP6 =PA13 GP13=PA14 GP20=PB9 GP27=PB14
* = PWM capable (TIM3)
SPI: GP11=SCK, GP10=MOSI, GP9=MISO
SWD: GP6=SWDIO, GP13=SWCLK
I2C: GP2=SDA, GP3=SCL (hardware pull-ups)

Drivers

Driver	Import	Status
RTk.GPIO (default)	import anyio.GPIO as GPIO	Full (28 pins, PWM, SPI)
Arduino	import anyio.arduino.GPIO as GPIO	GPIO only, 115200 baud
Console	import anyio.console.GPIO as GPIO	Simulator
GUI	import anyio.gui.GPIO as GPIO	Placeholder
Network	import anyio.net.GPIO as GPIO	Placeholder

Dual firmware auto-detect: v2.2 (enhanced, PWM/SPI/Reset) vs v1 (legacy, GPIO only).

Firmware

Version	File	Features
v2.2 (current)	RTk.GPIO-FW	GPIO + PWM + SPI + Pull + Reset + Version
v1 (original)	RTkGPIOV1_NUCLEO_F030R8.bin	GPIO + Pull only

Flashing

Requires: ST-LINK V2 (with NRST), openocd, arm-none-eabi-gcc (for recompilation).

openocd -f interface/stlink.cfg -f target/stm32f0x.cfg \
-c "reset_config srst_only connect_assert_srst" \
-c "init" -c "reset halt" \
-c "flash write_image erase firmware.bin 0x08000000" \
-c "verify_image firmware.bin 0x08000000" \
-c "reset run" -c "shutdown"

SWD header: 1=SWDIO, 2=SWCLK, 3=RST, 4=GND.

Changelog

v2.2 (2026-04-07)

• PWM via raw TIM3 registers (no mbed PwmOut — avoids TIM1/us_ticker conflict)
• 6 PWM pins: GP8, GP9, GP10, GP18, GP25, GP26
• Protocol: W (freq), P (duty), X (stop)
• Python: pwm_start(), pwm_duty(), pwm_stop(), tone()

v2.1 (2026-04-07)

• Full v2 protocol: SPI (~), Reset (R→OK), Version (V), Pull (U/D/N)
• 28 GPIO pins (GP0–GP27)
• Dual v1/v2 firmware auto-detect via R probe
• Compiled from v1 mbed-dev base (HSI clock fallback for 12MHz board)

v2.0-py3 (2026-04-07)

• Python 3 rewrite: 10 bugs fixed across all drivers
• Auto-detect single USB device, no interactive prompt needed

License

See LICENSE file.