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SN65DSI86: SN65dsi86 i2c dump showing Null values

cyriac toms
Prodigy 130 points
Part Number: SN65DSI86
Other Parts Discussed in Thread: DSI-TUNER

Tool/software:

SN65dsi86 is connected with an i2cbus number 3.   when i give i2cdump its showing xx values for every register. i am connecting this bridge with mipi dsi but the bridge connection is not happening is it the issue with the i2c which is giving null values or anyother issues in which the bridge is not getting attached with the sn65dsi86.

  • 0
    TI__Mastermind 37315 points

    Hi Cyriac,

    I saw in a previous E2E you were asking about I2C address info on the SN65DSI86. You are using a custom PCB with the SN65DSI86 correct?

    If you are not seeing a response from the device when reading from the I2C registers, the following needs to be checked

    • SN65DSI86 EN pin is asserted
    • I2C bus between the I2C controller and the SN65DSI86 matches VCCIO
    • I2C data rate at or below 400kbps
    • Correct I2C address is used

      There are registers in the SN65DSI86 with specified default values. It is expected for these to match

      Best,

      Jack

    • 0 in reply to Jack Scherlag
      Prodigy 130 points

      it was an issue with VCCIO pin. Also i have one doubt in connection with mipi dsi connection with sn65dsi can you help me in that the bridge connection

    • 0 in reply to cyriac toms
      TI__Mastermind 37315 points

      Hi Cyriac,

      Are you able to elaborate on the DSI connection issues you are having with the SN65DSI86? Are you not seeing output from the eDP interface when DSI is enabled?

      There is a color bar generator built into the SN65DSI86 that outputs only on the eDP interface. This can be useful for confirming that there is only an issues with the DSI interface and not the eDP interface. Have you tried the color bar generator?

      If you do not already have the DSI-Tuner tool for configuring the SN65DSI86, I recommend downloading it. See the link below.

      https://e2e.ti.com/support/interface-group/interface/f/interface-forum/825302/sn65dsi83-dsi-tuner-tool-needed

      Best,

      Jack

    • 0 in reply to Jack Scherlag
      Prodigy 130 points
      Jack Scherlag said:
      Are you able to elaborate on the DSI connection issues you are having with the SN65DSI86? Are you not seeing output from the eDP interface when DSI is enabled?

      Yess ,MIPI DSI and sn65dsi86 bridge connection is done. The output from the bridge need to be connected with differnt types of dsiplay panels by fetching the edid data from the panel so how to make it work. Any devictree configuration need to be done.

    • 0 in reply to cyriac toms
      TI__Mastermind 37315 points

      Hi Cyriac,

      EDID data from the display is transferred over the DP AUX channel. There are two ways to read from the EDID block in the display:

      1. Direct reads using EDID I2C address set in I2C_ADDR_CLAIM0

      2. Native DP aux reads and writes (Indirect method)

      The indirect method is outlined in section 8.4.5.3.2 in the datasheet. It is more complex since the user has to manually program the DP AUX registers for reading/writing.

      The direct method only requires that the I2C controller support clock stretching and the I2C_ADDR_CLAIM0 register be programmed. After writing 0x1 to SN65DSI86 register 0x60, the I2C controller can read from the EDID provided that is set at I2C address 0x50.

      Can you try

      • Setting SN65DSI86 register 0x60 = 0x1
      • Reading from I2C address 0x50 on the same bus as the SN65DSI86

      If the EDID I2C address is different than 0x50 the EDID will not be read.

      Best,

      Jack

    • 0 in reply to Jack Scherlag
      Prodigy 130 points

      I am using aTUSB546 in between does tusb is making the sn65dsi to transfer data over aux display. Do i have to add anything inside the devicetree node of sn65dsi to make the edid to wok.

    • 0 in reply to cyriac toms
      Prodigy 130 points

      the bridge connection is not happening if i connect  panel with without driver in compatible property in the devicetree. So when i add the panel with a driver the display properties are taken so that EDID data is not taken because of the timing property already in the driver.Is there any generic drivers to assign it so that EDID can be done.    I am using yocto linux for imx8mp

    • 0 in reply to cyriac toms
      TI__Mastermind 37315 points

      Hi Cyriac,

      My assistance is limited to the SN65DSI86 device. I cannot provide assistance with linux drivers or linux development. Are you not able to make a manual command to read display EDID?

      E2E FAQ: Link

      Jack