DS90UB941AS-Q1: 941-948 lock status is normal, but accessing the 948 register failed

Hello Honle,

Can you provide some additional information about your setup here?

- What kind of cable is being used between the 941AS/948?

- What hardware is being used? TI EVM HW or a custom PCB? Can you share a picture? 

- Is there a DSI source active at the input of the 941AS?

- Can you share a full register dump from the 941AS for review?

Best Regards,

Casey 

- What kind of cable is being used between the 941AS/948?
Reply: STQ  --LVDS

- What hardware is being used? TI EVM HW or a custom PCB? Can you share a picture?
Reply:a custom PCB，pucture

- Is there a DSI source active at the input of the 941AS?
Reply: yes

- Can you share a full register dump from the 941AS for review?
Reply: Sorry, as this is a client machine, I do not have dump data。

Honle,

In order to debug this further I think we will need to be able to access the 941AS registers to look at the diagnostic info. For example I am trying to understand if there are back channel errors occurring which is leading to a loss of remote communication. 

Also are you able to share the schematics for both sides?

Best Regards,

Casey 

We are unable to provide register information at the moment. Please ask under what circumstances there may be a reverse channel error.

Honle,

The most common reasons for reverse channel error would be:

- Incorrect schematic configuration, especially related to the DOUT/RIN high speed path (review schematics)

- Incorrect register settings on either the SER or DES sides (review register dumps)

Best Regards,

Casey 

Perhaps my expression was not complete enough, this is not a necessary issue. The vehicle occasionally experiences black screen issues, so based on current logs, only this situation has been analyzed.

Honle,

What support exactly are you requesting here?

Best Regards,

Casey 

What situations of 941/948 can cause such occasional problems?

occasional  problems:

Using 941 on the host side and 948 on the screen side, there was a failure to access the 948 side, but the lock was detected to be normal.

The 941 side register is configured as 0x03=0xda; 0x17=0x9e;

Recently, the status was normal, but in the middle there were 0xc4=0x18, 0x5a=0x19;

Honle,

For the communication issue where LOCK is high but communication is broken, that sounds like a back channel issue (941AS is getting back channel errors on the received back channel). For the status regs you just showed, it seems like you are also losing forward channel lock - possibly intermittent. 

For both, I would suggest to check:

- Incorrect schematic configuration, especially related to the DOUT/RIN high speed path (review schematics)

- Incorrect register settings on either the SER or DES sides (review register dumps)

Best Regards,

Casey