GEX protocol documentation
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gex-docs/UNIT_SPI.md

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SPI master

  • Can drive shift registers or communicate with any SPI based devices.
  • Configurable speed, polarity and phase
  • Up to 16 slave select signals
  • Supports multicast (write to multiple slaves at once)

NOTE: To use Multicast with bi-directionally connected devices, the MISO pins should be connected through protection resistors to prevent a short circuit on signal collision.

Commands

QUERY (0x00)

Write and read some bytes.

The write and read sections can overlap if needed; some devices use this to report a status word while the command is being written. 0x00 is output on MOSI while collecting a response.

If the overlap is not desired (first write, then read), set the number of discarded bytes equal to the number of written bytes.

Request:

  • u8 - slave number 0-16
  • u16 - number of discarded MISO bytes before collecting the response
  • u16 - response length (bytes)
  • u8[] - bytes to write

Response:

  • u8[] - received bytes

MULTICAST (0x01)

Request:

  • u16 - slaves (packed)
  • u8[] - bytes to write

Events

No events defined for this unit type.