USB-MODEVM Protocol
58
SLAU738 – September 2017
Copyright © 2017, Texas Instruments Incorporated
USB-MODEVM Protocol
If the command is sent with no problem, the returning byte [0] should be the same as the sent one
logically ORed with 0x20 - in the first example, the returning packet should be:
[0] 0x31
[1] 0xA0
[2] 0x02
[3] 0x05
[4] 0xAA
[5] 0x55
If for some reason the interface fails (for example, the I
2
C device does not acknowledge), it would come
back as:
[0] 0x51
--> interface | INTF_ERROR
[1] 0xA0
[2] 0x02
[3] 0x05
[4] 0xAA
[5] 0x55
If the request is malformed, that is, the interface byte (byte [0]) takes on a value which is not previously
described, the return packet would be:
[0] 0x93
--> the user sent 0x13, which is not valid, so 0x93 returned
[1] 0xA0
[2] 0x02
[3] 0x05
[4] 0xAA
[5] 0x55
The previous examples used writes. Reading is similar:
Read two bytes from device starting at register 5 of an I
2
C device with address A0:
[0] 0x01
[1] 0xA0
[2] 0x02
[3] 0x05
