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SPI Guide

Use this guide to verify SPI support, enumerate devices, and run a simple transfer with the Omega4.

1. Prerequisites​

  • Firmware with SPI enabled (Omega4 support starts at v0.0.7).
  • spi-tools package.

Install tools if needed:

opkg update
opkg install spi-tools

2. Find the SPI device​

List SPI character devices:

ls /dev/spidev*

If multiple buses are available, list kernel messages to identify the active controller:

dmesg | grep -i spi | tail -n 20

3. Quick transfer test​

spidev_test sends and receives data over an SPI device. Replace <bus> and <cs> with your device path:

spidev_test -D /dev/spidev<bus>.<cs> -s 1000000 -p "Omega4"

If your peripheral echoes data, you should see RX bytes printed in the output.

4. Set SPI parameters (example)​

Adjust mode, speed, and word size as needed for your device:

spidev_test -D /dev/spidev<bus>.<cs> -s 5000000 -b 8 -m 0 -p "\x9f"

5. Troubleshooting​

  • No /dev/spidev*: confirm the device tree enables the SPI controller and the spidev node for the EVB header.
  • Transfers fail: check wiring, chip select, and required SPI mode/clock.
  • Bus hangs: power-cycle the peripheral and retry with a lower speed.