DS90UB948-Q1: distribution problem of I2C and GPIO signal of back channel under 2-lane input mode

Hi Sherry,

Are you currently experiencing issues with GPIO/I2C communications through the backchannel?

Information is sent bidirectionally utilizing both the forward and back channels, which operate at different rates.  The backchannel rate is configured by the deserializer.

In normal mode, the GPIOs are mapped to their respective ports (DOUT0, DOUT1, etc..).  On the serializer, please use the TX_PORT_SEL registers to control port access.

For the 947 refer to table 1,2 and 3 for GPIO configuration, in the datasheet, found here: https://www.ti.com/lit/gpn/ds90ub947-q1

Sincerely,
Bryan Kahler

Hi Bryan,

Sorry for the late reply! Yes, my customer encountered black screen issue two weeks ago. 948's GPIO controls the brightness of the screen, and the screen touch function is realized by I2C. When the black fault occurs, the touch function still works. Finally, it shows that the connector is the root cause. Before finding the root cause, my customer asks me a question as below,

They use dual link mode(lane 1& lane 2), does I2C transmit in which lane, lane 1 or lane 2? does GPIO transmit in which lane, lane 1 or lane 2?

In my understanding,

1. About I2C,  if set bit1(PORT1_SEL)=1, then I2C will transmit in lane 2. If set bit0(PORT0_SEL)=1, then I2C will transmit in lane 1.

2. About GPIO/DGPIO, lane 1 only can transmit the GPIO signal, and lane 2 only can transmit the DGPIO signal.

Is my understanding correct about the above two points?

Thanks & Best Regards,

Sherry

Hi Bryan,

Clear. Thanks for your help!

Conform one more time, in dual link mode (one des connected), i2c traffic can't be sent over tx1, right?

Thanks & Best REgards,

Sherry

Hi Bryan,

Clear! Thank you very much!

Best Regards,

Sherry