- This is not a question looking for an answer, just a question with an answer that might help someone else.
As a working example let’s say that:
- the SPI Master must be able to send 1, 2, and 5-byte messages.
- the SPI Slave has a way to identify the messages as they roll in.
- all of the messages have to be received by the same MIBSPI device.
MIBSPI Master
- For all outbound messages define a TG:
- sized to match the message size.
- associated with the same physical Chip Select.
- When sending using the MIBSPI driver API:
- specify the TG that matches the message you are trying to send.
- the CS will go active low for the duration of the data send if CSHOLD is set.
MIBSPI Slave
- Create a “Shadow” of the slave's Chip Select by tying it to GIOA[x].
- Define single TG sized to fit the largest TG sent by the SPI Master.
- Configure the GIOA[x] to notify on the rising edge of the Chip Select.
- In the GIOA[x] notification callback
- set GCR1.SPIEN = 0 to deactivate the MIBSPI[x] device.
- set GCR1.SPIEN = 1 to reactivate MIBSPI[x], this is a partial reset of key registers and key to this working.
- Use the MIBSPI API call to read the received data.
- Identify the received message by examining its contents.
How does this work?
- When the MIBSPI Master sends a 5-byte message
- it is received and processed w/o errors and there is a TG Complete indication available.
- When the MIBSPI Slave receives a 1 or 2 byte message
- there is no TG Complete indication, it's a partial message that needs to be read out immediately.
- the toggling 0->1 of GCR1.SPIEN in the notification callback finalizes the transfer and sets the received data pointer back to the start of the buffer.
