Read and control I2C and SPI peripherals on supported boards.
Use the i2c and spi tools to interact with sensors, displays, and other peripherals connected to the board.
# 1. Find available buses
i2c detect
# 2. Scan for connected devices
i2c scan (bus: "1")
# 3. Read from a sensor (e.g. AHT20 temperature/humidity)
i2c read (bus: "1", address: 0x38, register: 0xAC, length: 6)
# 4. SPI devices
spi list
spi read (device: "2.0", length: 4)
Most I2C/SPI pins are shared with other subsystems on some boards. You must configure pinmux before use.
See references/board-pinout.md for board-specific commands.
Common steps:
/etc/init.d/S30wifi stopmodprobe i2c-devdevmem (board-specific)i2c detect and i2c scanconfirm: true — always confirm with the user firstSee references/common-devices.md for register maps and usage of popular sensors:
AHT20, BME280, SSD1306 OLED, MPU6050 IMU, DS3231 RTC, INA219 power monitor, PCA9685 PWM, and more.
| Problem | Solution |
|---|---|
| No I2C buses found | modprobe i2c-dev and check device tree |
| Permission denied | Run as root or add user to i2c group |
| No devices on scan | Check wiring, pull-up resistors (4.7k typical), and pinmux |
| Bus number changed | I2C adapter numbers can shift between boots; use i2c detect to find current assignment |
| WiFi stopped working | I2C-1/SPI-2 share pins with WiFi SDIO; can't use both simultaneously |
devmem not found | Download separately or use busybox devmem |
| SPI transfer returns all zeros | Check MISO wiring and device power |
| SPI transfer returns all 0xFF | Device not responding; check CS pin and clock polarity (mode) |