Appendix G USB-MODEVM Protocol
G.1
USB-MODEVM Protocol
Appendix G
www.ti.com
The USB-MODEVM is defined to be a Vendor-Specific class, and is identified on the PC system as an
NI-VISA device. Because the TAS1020 has several routines in its ROM which are designed for use with
HID-class devices, HID-like structures are used, even though the USB-MODEVM is not an HID-class
device. Data is passed from the PC to the TAS1020 using the control endpoint.
Data is sent in an HIDSETREPORT (see
Table G-1
):
Table G-1. USB Control Endpoint
HIDSETREPORT Request
Part
Value
Description
bmRequestType
0x21
00100001
bRequest
0x09
SET_REPORT
wValue
0x00
don't care
wIndex
0x03
HID interface is index 3
wLength
calculated by host
Data
Data packet as described below
The data packet consists of the following bytes, shown in
Table G-2
:
Table G-2. Data Packet Configuration
Byte Number
Type
Description
0
Interface
Specifies serial interface and operation. The two values are logically ORed.
Operation:
READ
0x00
WRITE
0x10
Interface:
GPIO
0x08
SPI_16
0x04
I2C_FAST
0x02
I2C_STD
0x01
SPI_8
0x00
1
I
2
C Slave Address
Slave address of I
2
C device or MSB of 16-bit reg addr for SPI
2
Length
Length of data to write/read (number of bytes)
3
Register address
Address of register for I
2
C or 8-bit SPI; LSB of 16-bit address for SPI
4..64
Data
Up to 60 data bytes could be written at a time. EP0 maximum length is 64. The return
packet is limited to 42 bytes, so advise only sending 32 bytes at any one time.
Example usage:
Write two bytes (AA, 55) to device starting at register 5 of an I
2
C device with address A0:
[0]
0x11
[1]
0xA0
[2]
0x02
[3]
0x05
[4]
0xAA
[5]
0x55
46
USB-MODEVM Protocol
SLAU261 – November 2008
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