DS90UB954-Q1: Pattern generator

Hello, thank you for your quick response. I have seen that software but I needed to run it on linux. I'm going to see if I can find a way to use it anyway.

It is a good option, I will take it into account, thank you very much!

I take this opportunity to consult about the problem that I have which is the cut of the transmission of video images. Could it be due to channel saturation or errors in the configuration of the SERIALIZER-DESERIALIZER? 

Hello Adrian,

Can you give more details on your system configuration? How many sensors going into the hub? What are the video rates and video formats for those videos? How many CSI-2 lanes are being used? What is the configured CSI-2 data rate?

Best Regards,
Casey 

Here I leave a diagram of the connection.

A camera is connected to each serializer, and then also a single one of these, connected to port 0 in the deserializer. The physical connection is made using a 5 meter coaxial cable with a 50 ohm impedance that I understand is the correct thing to do.

The video rate is 60 fps, YUY2 format,1824 x 940 pixeles, and 2 CSI-2 lanes are being used at 1.6 Mbps on the 954 side, and 2 Mbps on the 953 side.

Hello Adrian,

Can I just clarify on one point above? 

Adrian Palumbo said:

2 Mbps on the 953 side.

What do you mean by this? What is the per-lane CSI-2 rate on the 953 side and how many CSI-2 lanes are used? 

Best Regards,

Casey 

Hello Casey, I clarify the last part of the message for a better understanding. Sorry if I explained wrong
or forgot any information.

The video rate is 60 fps, YUY2 format,1824 x 940 pixels. The 954 uses 2 CSI-2 lanes with a rate of 1.6 Gbps per-line,
and the 953 uses 4 CSI-2 lanes with a rate of 50 Mbps per-line because it operates in synchronous mode.

Hello Adrian,

The 953 has a minimum per-lane CSI-2 rate of 80Mbps per the datasheet operating conditions. So 50Mbps lane rate may be part of the issue here. Can you please fix your 953 side configuration to ensure that the input CSI-2 lane rate is >=80Mbps/lane?

I'm not sure your statement about the 953 CSI-2 rate makes sense because the video format 1824x940@60, YUV2 should take more bandwidth than 50Mbps/lane on the 953 CSI-2 input side 

Best Regards,

Casey 

Yes, your analysis is correct. Check and data on entry to 953 comes at 800 Mbps / lane. Sorry for the mistake and thank you.

Hello Adrian,

Can you do a quick check when this issue occurs can you read back 0x4D and 0x4E registers in the 954? Also make sure to read them back after powering up the system and starting the image data to clear any transient errors. I'm trying to understand if your issue is losing LOCK or buffer error, etc. 

Best Regards,

Casey 

Hello, I followed the steps you told me, and the results of reading the registers after cutting the image are:

• Register 0x4D: 0x33 
• Register 0x4E: 0xFD

Hey Adrian,

Just to be extra clear - you read the registers first to clear the transient errors, and then read them again to give the above?

Best Regards,

Casey 

Hello, I did that as you told me. I tell you the steps that I followed:

Start a video stream and then read the registers to clean them. Once they were clean, they gave me the following values: ​​

• Register 0x4D: 0x03 and register 0x4E: 0x0C

Wait for the error to occur, transmission cutoff, and I got the following values:

• Register 0x4D: 0x33 and register 0x4E: 0xED

I clarify that for different tests the register 0x4E returns the value of 0xFD.

Hello Adrian,

Ok so what the registers indicate clearly is that you are losing LOCK between the SER and DES at some point during transmission which is causing data errors or lost data. Can you please share some pictures of your setup so we can understand what the interconnects look like? It may also be useful to run the Margin Analysis program in ALP to help get a better picture of the link margin in your system or switch to a different cable to see if the issue improves: 

https://www.ti.com/lit/pdf/snla301 

https://www.ti.com/lit/pdf/snlu243

Best Regards,

Casey 

Hello Casey, I am sending you the photos that you asked me before.

The first photo shows the connection from the serealizer to a COAXIAL cable of 3 meter (RG58 A-U) ,and finally it goes to the deserealizer as seen in the second photo.

I'm going to take your recommendation to change the cable, and I wanted to ask you which of these two that I have available would serve me (attached datasheets of each one).

• https://catalog.belden.com/techdata/EN/8219_techdata.pdf
• https://media.digikey.com/pdf/Data%20Sheets/Molex%20PDFs/50CX-42.pdf

What type of cable do you recommend using, if these two do not work for me or to have other options, if I want to have a length of 15 m? And if I want a longer length?

Thank you!

Hi Casey,

Thank you very much for your time and the advice you gave me. These days I will be doing tests and I will tell you the results.

Hello Adrian,

Ok please let us know if you need any additional help 

Best Regards,

Casey 

Hello Casey, I wanted to say that you helped me a lot because I can have the camera on, sometimes, for about an hour.

This was previously impossible because after a few seconds the connection dropped.

However, there are times that when it starts up I lose the connection and then in the second attempt it works fine, or other cases that it remains good for about 10 or 15 minutes and then the connection is lost.

I can think that maybe now it is not a LINK problem and it comes from the other side.

Thank you.

Hello Adrian,

What sort of support are you looking for exactly? If there is a technical problem you would like help with, can you provide specifics of the what you are seeing, what symptoms are occurring, and how you reproduce the issue? When you say connection is lost, do you mean that LOCK is permanently low?

Best Regards,

Casey 

Hi Casey,

I read the registers you told me last time and I get the following values:

• Register 0x4D: 0x17 and register 0x4E: 0xED

I can see that in register 0x4D the LOCK is high because it is indicated by bit 0, but there is a change in it because it is indicated by bit 4. But my question is if there is no way to make it less sensitive and not to cut the connection, that is, to tolerate that error and continue to transmit video.

I do not care if I lose a frame or decrease the quality, my main focus is that the connection is not cut and continues to transmit video tolerating errors. Can I do this by changing any settings in the internal registers?

Thank you!

Hello Adrian,

The most robust way to fix your issue is to resolve the SI component of your system since it sounds like the errors are coming as a result of temporary loss of LOCK. There's really no way to prevent LOCK from dropping if the SI is out of spec since the deserializer needs to be able to recover the link clock and encoding to be able to receive data and construct CSI-2 packets. By default the part will forward packets with errors if there are error coming as a result of link quality, but by the time you are getting loss of LOCK events, that means the SI is at a point where the video is un-recoverable - not just one or two pixel errors

Best Regards,

Casey 

Hi Casey,

Thank you very much for your prompt response, but I don't understand what you mean when you say "solve the SI component of your system". What is the SI component?

The rest of the message about the loss of the LOCK I understand perfectly.