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DS90UB962-Q1: questions about Port 0 / 1/2/3 use

Part Number: DS90UB962-Q1

Hi team

customer use 962 connect 4 camera modules. they need detect whether the port camera is connect or not. if not, they will disable this port in reg 0x20.

but, now we have some problems

1. if disconnect Port 0, let it float, the SOC can receive the others three camera interrupt but the data of camera sent is wrong.

2. connect all Port 0 to 3, power on, every thing is ok. but if disconnect Port 0 during the work time, only Port 1 can work normally, but other two Port 2 and Port 3 will work wrong, can not get normal data.

3. based on step 2, if connect Port 0 at that time, every thing will recover and data normal.

so, we want to know why the Port 0 will affect the others Port working status? Can you share the internal work frame?

The 962 work in interleaving mode.

thank you

  • Hi Betty,

    The way that Line-Interleaved synchronized forwarding works is that line data is taken from the FIFO buffer at each Rx port buffer and then forwarded as a superframe, with the line data from each port interleaved (See Section " Line-Interleaved CSI-2 Forwarding" in the 962 datsheet). If Rx Port 0 is disconnected, then its FIFO buffer will not have data and this will cause the sync to be lost.

    For Line-Interleaved synchronized forwarding mode to work, all of the video data at each port needs to be synchronized. If you disconnect a camera from the 962's Rx port, then this will desynchronize the forwarded video data and cause issues. You can configure your system to perform Line-Interleave with 3 cameras instead of the original 4 cameras, but you need to make sure they are synchronized. To get Line-Interleaved synchronized forwarding to work again, you would need to write to register 0x20 to disable Port 0. Also, make sure to select synchronous with line interleaving in register 0x21.

    Or you could simply use Round-Robin forwarding mode and not have to worry about these sync issues after disconnecting a camera at a port.


    Justin Phan

  • Hi Justin,

    now,  with inter -leaved mode, we only use Port 1/2/3, they are synchronous, disable Port 0 at 0x20, read 0x22=0x01, show they three camera is synchronous.

    read 0x73-76 of PORT1/2/3, these three camera resolution is normal, 1280*800. but the SOC receive data show the PORT1 wrong. once connect Port0, everything is ok.

    any other suggestions

    thank you

  • Hi Justin

    checked with SOC side, they will use VCID to distinguish different sensor, so customer use different VCID in inter-leaved mode. if they use the same VCID for example VC 0, the SOC think only port 0 have data.

    so, I have some questions

    1. for inter-leaved mode, can they use different VCID? or must be the same ? any problems with different VCID

    2. if only PORT1/2/3 used, what's the frame start? FS0 or FS1? what's the content of FS? does this have VCID information?

    3. if only PORT1/2/3 used, does the data of CSI-2 transmit have PORT 0 data or only PORT 1/2/ should be FS1-S1LI-S2L1-S3L1-S1L2.. right?

    thank you

  • Hi Betty,

    1. For Line-Interleaved mode, all input video streams must have the same VC-ID. You can try to change the VC-ID used, but make sure Ports 1/2/3 all have the same VC-ID (register 0x70 or 0x71).
    2. The example scenario given in Section Line-Interleaved CSI-2 Forwarding of the datasheet is for when all 4 ports are used for Line-Interleaved forwarding. In the example, FS0 refers to the Frame Start packet from Port 0. The FS and FE from the other ports are discarded, in order to forward a line-interleaved superframe. But it is possible to use Line-Interleaved forwarding with only 3 ports instead. If Rx Ports 1/2/3 are used, then the frame start would be FS1. FS and FE are short packets. And its structure is shown in Figure 7-8. CSI-2 Short Packet Structure in the datasheet. VC-ID information is in the long packet. See Table 7-12. CSI-2 Long Packet Structure Description in the datasheet.
    3. If you disable Port 0 and only use Port 1/2/3, then you are correct in that the video frame should be: 
      1. FS1 – S1L1 – S2L1 – S3L1 – S1L2 – ... – FE1

    If reconnecting Port 0 fixes the problem, then your application might still be configured to use Port 0 (FS0 and FE0) instead of FS1 and FE1. 

    Could you provide the portion of code that was used to configure Line-Interleaving mode? It should be similar to the code example shown in Section Code Example for Line-Interleaved CSI-2 Forwarding in the datasheet.


    Justin Phan