SLAU855A June   2021  – March 2022 TLV320AIC3101 , TLV320AIC3104 , TLV320AIC3104-Q1 , TLV320AIC3105 , TLV320AIC3106 , TLV320AIC3106-Q1 , TLV320AIC3107 , TLV320AIC3109-Q1 , TLV320AIC34

 

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3.4 USB-MODEVM Protocol

The USB-MODEVM is defined as 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 that 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 are passed from the PC to the TAS1020 using the control endpoint.

As Table 3-3 describes, data are sent in an HIDSETREPORT.

Table 3-3 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

Table 3-4 lists the bytes that comprise the data packet.

Table 3-4 Data Packet Configuration
Byte Number Type Description
0 Interface Specifies the serial interface and operation. The two values are logically OR'd.
Operation:
READ 0x00
WRITE 0x10
Interface:
GPIO 0x08
SPI_16 0x04
I2C_FAST 0x02
I2C_STD 0x01
SPI_8 0x00
1 I2C slave address Slave address of the I2C device or the MSB of the 16-bit register address for SPI
2 Length Length of data to write/read (number of bytes)
3 Register address Address of the register for I2C or 8-bit SPI; LSB of the 16-bit address for SPI
4...64 Data Up to 60 data bytes can 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 usages:

Write two bytes (AA, 55) to the device starting at register 5 of an I2C device with address A0:

[0] 0x11

[1] 0xA0

[2] 0x02

[3] 0x05

[4] 0xAA

[5] 0x55

Do the same with a fast mode I2C device:

[0] 0x12

[1] 0xA0

[2] 0x02

[3] 0x05

[4] 0xAA

[5] 0x55

Now do the same with an SPI device that uses an 8-bit register address:

[0] 0x10

[1] 0xA0

[2] 0x02

[3] 0x05

[4] 0xAA

[5] 0x55

Do the same process for a 16-bit register address, as found on parts like the TSC2101. Assume the register address (command word) is 0x10E0:

[0] 0x14

[1] 0x10

Note:

The I2C address now serves as the MSB of the register address.

[2] 0x02

[3] 0xE0

[4] 0xAA

[5] 0x55

In each case, the TAS1020 returns, in an HID interrupt packet, the following:

[0] interface byte | status
status:
REQ_ERROR 0x80
INTF_ERROR 0x40
REQ_DONE 0x20
[1] For I2C interfaces, the I2C address is as sent
For SPI interfaces, the read back data from the SPI line for transmission of the corresponding byte is as sent
[2] Length is as sent
[3] For I2C interfaces, the register address is as sent
For SPI interfaces, the read back data from the SPI line for transmission of the corresponding byte is as sent
[4..60] The echo of the data packet is sent

If the command is sent with no problem, the returning byte [0] must be the same as the sent one logically or'd with 0x20. In the first example usage, the returning packet is:

[0] 0x31

[1] 0xA0

[2] 0x02

[3] 0x05

[4] 0xAA

[5] 0x55

If for some reason the interface fails (for example, the I2C device does not acknowledge), the returning byte comes 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 that is not described above, the return packet is:

[0] 0x93 → the user sent 0x13, which is not valid, so 0x93 is returned

[1] 0xA0

[2] 0x02

[3] 0x05

[4] 0xAA

[5] 0x55

The examples above used writes. Reading is similar:
Read two bytes from the device starting at register 5 of an I2C device with address A0:

[0] 0x01

[1] 0xA0

[2] 0x02

[3] 0x05

The return packet is:

[0] 0x21

[1] 0xA0

[2] 0x02

[3] 0x05

[4] 0xAA

[5] 0x55

This result is assuming that the values written above starting at register 5 were actually written to the device.