hardware

Files (3)

• SKILL.md
• board-pinout.md · references/
• common-devices.md · references/

SKILL.md (first lines)

# Hardware (I2C / SPI)

Use the `i2c` and `spi` tools to interact with sensors, displays, and other peripherals connected to the board.

## Quick Start

```
# 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)
```

## Before You Start — Pinmux Setup

Most I2C/SPI pins are shared with WiFi on supported boards. You must configure pinmux before use.

See `references/board-pinout.md` for board-specific commands.

**Common steps:**
1. Stop WiFi if using shared pins: `/etc/init.d/S30wifi stop`
2. Load i2c-dev module: `modprobe i2c-dev`
3. Configure pinmux with `devmem` (board-specific)
4. Verify with `i2c detect` and `i2c scan`

## Safety

- **Write operations** require `confirm: true` — always confirm with the user first
- I2C addresses are validated to 7-bit range (0x03-0x77)
- SPI modes are validated (0-3 only)
- Maximum per-transaction: 256 bytes (I2C), 4096 bytes (SPI)

## Common Devices

See `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.

## Troubleshooting

| 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) |

From AbdullahMalik17/malikclaw, MIT.

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