SN65DSI86: Question about sn65dsi86

Hi Jimmy,

1. When the system is working as expected, is there correct display output?

2. Please check whether the datasheet initialization sequence is followed, including enabling the output, link training procedure, and DSI settings.

3. With test pattern mode, is there the display output correct as expected?

4. Are there any errors shown on 0xF0 -0xF8 registers when this issue occurs?

To program the device, you can use the calculator tool shared here: [FAQ] SN65DSI8x Programming Tools 
Please refer to the "READ ME" sheet in the file, and use the register settings to program the device. You can enable test pattern to output an internally generated pattern.

Best regards,
Ikram

Hello Ikram：

1. When the system is working as expected, is there correct display output?
---The phenomenon of flashing bright lines is a probabilistic occurrence and not always present; Most of the time, there is no abnormal phenomenon displayed;
2. Please check whether the datasheet initialization sequence is followed, including enabling the output, link training procedure, and DSI settings.
---Yes, it has already been checked.
3. With test pattern mode, is there the display output correct as expected?
---No, there's the same problem. Under the same porch value setting as required by the screen parameters, the pattern display will also have a probability of flashing color bars
4. Are there any errors shown on 0xF0 -0xF8 registers when this issue occurs?

---Simulating IIC, it is currently not convenient to detect these registers.

In addition, the customer has encountered this issue with a similar adapter chip solution. The solution is to ensure the synchronization integrity of the first frame image after power on. May I ask if the sn65dsi86 has a similar mechanism? Or is this issue related to synchronization.
Or how to investigate? Is there any interference causing the situation where there are several rows of pixels flashing at the bottom of the screen.

Hi Jimmy,

The 0xF0 - 0xF8 registers are for checking various errors. To narrow down the issue and find the root cause, it's one of the items we would need to check.  In the design there should be a way to read and write from the DSI86 registers to initialize it and run it as well. Could you please read these over I2C? And what do you mean by simulating I2C? 

There is no known issue of flashing or horizontal lines like this. So this would be cause by an error either in the timing programming or incoming video from the DSI source. 

Yes, this could be related to a synchronization issue if the DSI or reference clock rates do not match the programmed clock rates. Please check the programmed timings on the DSI86 and whether it matches the DSI source timings.


To summarize the next steps:

1. Please get a register dump of all the DSI86 available registers, so we can check how the device is programmed and also any reported errors (0xF0 - 0xF8, including synchronization and DP errors)

2. If the flashing and interference line occurs even with test pattern, then this could be due to a timing mismatch or clocking issue. Meaning the issue is still occurring without DSI incoming video and there is issue between DP output video and display. This may also be an issue with the display receiver or TCON.

Please check the display timings from it's datasheet, including active and blanking values. Share these if possible. Check the sync pulse widths and sync pulse polarity. What clock rate is used and is it using DSI or external reference clock?


3. Please check the initialization sequence in the datasheet. There are requirements for enabling the device, enabling video, and settings the DSI states. For example, the video registers need to be programmed to the exact timings of the incoming DSI video, and within the tolerance of the display, and the sequence has VSTREAM_ENABLE set at the end of initialization. The steps are listed in the "8.4.2 Power-Up Sequence" section.

Best regards,
Ikram