SPI - Full Duplex Transfer; 536-543 Bytes Out, 0+ Bytes In

Report Type: Interrupt IN / OUT
Report Size: 548 Bytes
Acknowledged By: Transactional reports in the range [0x80, 0xff] or Command Acknowledgement for USB failures

Report ID	Flags	Count LSB	Count MSB	Address	Payload
11000011	rrr 000 d t	cccccccc	cccccccc	00000 aaa	543 bytes

Report ID

HID Report ID. Always 0xc3.

This is effectively the seven most significant bits of the Payload field’s size (in bytes). The total number of bytes in the payload can be found by: <pre>(Report ID - 128) * 8 + rrr</pre>

Flags

Bits	Direction	Meaning
t	IN	Timeout flag; 1 if the transaction took too long, 0 if not. For an OUT Report this should be 0.
d	IN	Done flag; 1 if the transaction has completed, 0 if there are more IN Reports to follow. For an OUT Report this should be 0.
rrr	IN / OUT	The number of payload bytes contained in the last packet of the report (the ‘residual’). The total number of bytes in the payload can be found by: <pre>(Report ID - 128) * 8 + rrr</pre>.

Count

For an OUT Report this is the number of bytes that will be shifted from the MISO line and returned to the Host. This can be 0 if the transaction is write-only and the MISO data is to be discarded.

For an IN Report this is the number of bytes remaining to be shifted from the MISO line. If this field is 0 then it does not automatically mean that the transaction has completed as there might still be data being shifted onto the MOSI line; check the Done Flag (d) to determine when the stream of IN Reports has completed.

This field is Little Endian, ie. the Least Significant Byte of the word appears first. Bit numbering within the constituent bytes is unaffected.

Address

The Slave Select line that is asserted. The valid range is [0, 7]

Payload

A block of 543 bytes that will be shifted onto the MOSI line for an OUT report, or in from the MISO line for an IN report. Bits are shifted MSb-first. Only the first 536 + rrr bytes are meaningful, the rest are ignored or undefined.