GEX protocol documentation
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# SPI master
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- Can drive shift registers or communicate with any SPI based devices.
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- Configurable speed, polarity and phase
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- Up to 16 slave select signals
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- Supports multicast (write to multiple slaves at once)
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*NOTE:* To use Multicast with bi-directionally connected devices, the MISO pins should be
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connected through protection resistors to prevent a short circuit on signal collision.
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## Commands
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### QUERY (0)
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Write and read some bytes.
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The write and read sections can overlap if needed; some devices use this
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to report a status word while the command is being written. 0x00 is output on MOSI while collecting a response.
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If the overlap is not desired (first write, then read), set the number of discarded
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bytes equal to the number of written bytes.
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*Request:*
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- u8 - slave number 0-16
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- u16 - number of discarded MISO bytes before collecting the response
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- u16 - response length (bytes)
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- u8[] - bytes to write
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*Response:*
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- u8[] - received bytes
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### MULTICAST (1)
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*Request:*
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- u16 - slaves (packed)
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- u8[] - bytes to write
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## Events
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*No events defined for this unit type.*
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