H.0.0.2
USB Write Transaction Sequence
To issue a write command, the host must perform the following steps:
1. Host sends the Report ID byte, which is set to 0.
2. Host sends the Flags byte, where
•
Bit 6 is set to 0x1 to indicate the host wants a reply from the device. The device responds with the
NACK bit set if an unknown command was received or there was any error in processing the
command due to invalid parameters or other reasons..
•
Bit 7 is set to 0x1 to indicate a read transaction
3. Host sends the Sequence byte. When a single command is more than 64 bytes, it is sent as multiple
USB packets and the sequence byte is used to number the packets so the device can assemble them
in the right sequence. In other cases, this value is irrelevant and generally set to 0.
4. Host sends two bytes with the length of the data packet. This length denotes the number of data bytes
in the packet and excludes the number of bytes in steps 1 through 4. It denotes the total number of
bytes sent in steps 5 (command bytes) and 6 (data bytes).
5. Host sends three OpCode bytes: OpCode Byte 1 and OpCode Byte 2.
6. Host sends data appropriate to command.
7. After completion of this command, DLP NIRscan Nano responds with a packet that includes a byte
with the command requested by the host. This occurs only if bit 6 was set in the Flags byte.
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DLPU030B – June 2015 – Revised July 2015
DLP NIRscan Nano USB Communications
Copyright © 2015, Texas Instruments Incorporated