AeonDave raspberry-pi
Goal: Interface hardware peripherals (sensors, actuators, radios) with a Raspberry Pi running a standard Linux OS (Raspberry Pi OS).
1. Pinout & Buses
The 40-pin GPIO header provides multiple buses.
- Levels: GPIO logic is 3.3V. Connecting 5V signals directly will destroy the Pi.
- I2C: Pins 3 (SDA) and 5 (SCL). Requires enabling via
raspi-config. Built-in pull-up resistors (1.8kΩ) exist on these pins. - SPI: Pins 19 (MOSI), 21 (MISO), 23 (SCLK), 24 (CE0), 26 (CE1).
- UART: Pins 8 (TX) and 10 (RX). Usually mapped to
/dev/serial0(disables Bluetooth console on Pi 3/4).
2. Software Interfacing (Python)
Prefer gpiozero for simple UI/sensors and smbus2 or spidev for deep bus control.
I2C Scanner
sudo apt install i2c-tools
i2cdetect -y 1
Python I2C Example
from smbus2 import SMBus
with SMBus(1) as bus:
# Read a byte from device 0x48, register 0x00
b = bus.read_byte_data(0x48, 0)
3. Production Rules
- Power: The 5V pins bypass the polyfuse. Modulating heavy loads (motors) requires an external relay/MOSFET and separate power supply.
- Real-Time Limits: Linux is not a Real-Time OS. Fast bit-banging (like NeoPixels or strict timing protocols) will jitter unless offloaded to the PWM/DMA controllers or a co-processor (like an Arduino/Pico).