picoclaw/workspace/skills/hardware/references/board-pinout.md

Board Pinout & Pinmux Reference

LicheeRV Nano (SG2002)

I2C Buses

Bus	Pins	Notes
I2C-1	P18 (SCL), P21 (SDA)	Shared with WiFi SDIO — must stop WiFi first
I2C-3	Available on header	Check device tree for pin assignment
I2C-5	Software (BitBang)	Slower but no pin conflicts

SPI Buses

Bus	Pins	Notes
SPI-2	P18 (CS), P21 (MISO), P22 (MOSI), P23 (SCK)	Shared with WiFi — must stop WiFi first
SPI-4	Software (BitBang)	Slower but no pin conflicts

Setup Steps for I2C-1

# 1. Stop WiFi (shares pins with I2C-1)
/etc/init.d/S30wifi stop

# 2. Configure pinmux for I2C-1
devmem 0x030010D0 b 0x2   # P18 → I2C1_SCL
devmem 0x030010DC b 0x2   # P21 → I2C1_SDA

# 3. Load i2c-dev module
modprobe i2c-dev

# 4. Verify
ls /dev/i2c-*

Setup Steps for SPI-2

# 1. Stop WiFi (shares pins with SPI-2)
/etc/init.d/S30wifi stop

# 2. Configure pinmux for SPI-2
devmem 0x030010D0 b 0x1   # P18 → SPI2_CS
devmem 0x030010DC b 0x1   # P21 → SPI2_MISO
devmem 0x030010E0 b 0x1   # P22 → SPI2_MOSI
devmem 0x030010E4 b 0x1   # P23 → SPI2_SCK

# 3. Verify
ls /dev/spidev*

Max Tested SPI Speed

• SPI-2 hardware: tested up to 93 MHz
• spidev_test is pre-installed on the official image for loopback testing

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MaixCAM

I2C Buses

Bus	Pins	Notes
I2C-1	Overlaps with WiFi	Not recommended
I2C-3	Overlaps with WiFi	Not recommended
I2C-5	A15 (SCL), A27 (SDA)	Recommended — software I2C, no conflicts

Setup Steps for I2C-5

# Configure pins using pinmap utility
# (MaixCAM uses a pinmap tool instead of devmem)
# Refer to: https://wiki.sipeed.com/hardware/en/maixcam/gpio.html

# Load i2c-dev
modprobe i2c-dev

# Verify
ls /dev/i2c-*

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MaixCAM2

I2C Buses

Bus	Pins	Notes
I2C-6	A1 (SCL), A0 (SDA)	Available on header
I2C-7	Available	Check device tree

Setup Steps

# Configure pinmap for I2C-6
# A1 → I2C6_SCL, A0 → I2C6_SDA
# Refer to MaixCAM2 documentation for pinmap commands

modprobe i2c-dev
ls /dev/i2c-*

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NanoKVM

Uses the same SG2002 SoC as LicheeRV Nano. GPIO and I2C access follows the same pinmux procedure. Refer to the LicheeRV Nano section above.

Check NanoKVM-specific pin headers for available I2C/SPI lines:

• https://wiki.sipeed.com/hardware/en/kvm/NanoKVM/introduction.html

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Common Issues

devmem not found

The devmem utility may not be in the default image. Options:

• Use busybox devmem if busybox is installed
• Download devmem from the Sipeed package repository
• Cross-compile from source (single C file)

Dynamic bus numbering

I2C adapter numbers can change between boots depending on driver load order. Always use i2c detect to find current bus assignments rather than hardcoding bus numbers.

Permissions

/dev/i2c-* and /dev/spidev* typically require root access. Options:

• Run picoclaw as root
• Add user to i2c and spi groups
• Create udev rules: SUBSYSTEM=="i2c-dev", MODE="0666"