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Original question:

[FAQ] SN65DSI84: How to configure the SN65DSI84 and SN65DSI85 for single channel DSI to dual channel LVDS

SN65DSI84: register configuration with DSI-Tuner

Glenn Herrou
Prodigy 10 points
Part Number: SN65DSI84
Other Parts Discussed in Thread: DSI-TUNER

Hello TI Experts,

I have seen the FAQ on how to configure the SN65DSI84 with  DSI-Tuner. I have tried to configure the SN65DSI84 with single 4-lane DSI / Dual LVDS  for our 1280x1024p@60fps display but i have some remaining questions.

As far as I understand, our DSI clock frequency is fixed as the datasheet of the SOM connected to the SN65 DSI input specifies a frequency of 1.5 Gbps per lane. I am not sure what value to put in DSI-Tuner as DSI Ch A CLK. All my attempts seemed to result in incompatible values in the output tab.

Could you tell me how exactly I can compute the correct DSI CLK frequency from the 1.5 Gbps per lane value ?

The relevant documentation for our LVDS and DSI characteristics are as follows.

Our screen timings :

DSI interface from our SOM:

Thank you in advance for your answer,

Best Regards

Glenn

  • +1
    TI__Genius 13280 points

    Glenn,

    Could you tell me how exactly I can compute the correct DSI CLK frequency from the 1.5 Gbps per lane value?

    The correct DSI CLK frequency calculation does not include 1.5 Gbps directly in the calculation. Additionally, the four DSI data lanes per channel operating up to 1 Gbps per lane not 1.5.

    See below to calculate. From the datasheet you gave LVDSCLK = 54MHz.

    Step 8:

    Fill out the CLK inputs. The LVDS CLK frequency should be given in the timing table in the display datasheet (refer to step 3). For this display it is 70.6 MHz.

    You can use either the DSI CLK input or an external reference clock to source the LVDS CLK. This example uses the DSI CLK to source the LVDS CLK.

    To determine the DSI CLK frequency, use the following equation:

    Thanks,

    Zach

  • 0 in reply to Zach Dryer
    Prodigy 10 points

    Zach, thank you for your response.

    I think I misunderstood how we chose the DSI Clock. From what I understood, it was fixed to the value provided by the SOM datasheet.

    So, according to the calculation you provided, DSI CLK is 324MHz in my case. I should then find how to configure the DSI clk to this value on the SOM side. Do I understand this right ?

    Thanks,

    Glenn

  • +1 in reply to Glenn Herrou
    TI__Genius 13280 points

    Glenn,

    It sounds like you have the correct understanding. If you run into anymore issues feel free to start up another thread.

    If you have no other questions, please click the  "this resolved my issue" button.

    Thanks,

    Zach

  • 0 in reply to Zach Dryer
    Prodigy 10 points

    Thank you Zach, I'll try this out.

    Best regards,

    Glenn

  • 0 in reply to Glenn Herrou
    TI__Genius 13280 points

    Your welcome.

    Thanks,

    Zach