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DS90UB949-Q1: how to write EDID data to external EEPROM of DS90UB949?

Jinteng Tang
Prodigy 160 points
Part Number: DS90UB949-Q1
Other Parts Discussed in Thread: ALP

Tool/software:

I am debugging a board with DS90UB949 with ALP.

(1) With the following script, the EDID data can be written and read back correctly.

that is to say, read_edid is the same with exEDID what I write.

board.EDID_Write(0x0, exEDID, 256)

# Readback EDID read_edid = board.EDID_Read(0x0, 256)

print "EDID readback:"

print read_edid

(2) but after I power down and power up DS90UB949 board again.I read back the EDID data with the following script.

The EDID data is totaly different from what I write in step(1)

# Readback EDID read_edid = board.EDID_Read(0x0, 256)

print "EDID readback:"

print read_edid

My questions are

(1) with board.EDID_Write(0x0, exEDID, 256), where the EDID data is written? internal SRAM of DS90UB949?

(2) how to write EDID data to external EEPROM of DS90UB949?

Thanks

  • +1
    TI__Guru 65740 points

    Hi, 

    Your understanding is correct, using the EDID write will only go into the SRAM which will be wiped on next power cycle. 

    Jinteng Tang said:
    (2) how to write EDID data to external EEPROM of DS90UB949?

    External EEPROM is an external device from the 949, and will need flashed by other means according to the instructions/requirements of that particular IC.

    Regards, 

    Logan

  • 0 in reply to Logan Cummins
    Prodigy 160 points

    How to use EDID data in SRAM to update HDMI display property of PC side?

  • +1 in reply to Jinteng Tang
    TI__Guru 65740 points

    Hi Jinteng, 

    The EDID will be advertised automatically to the PC when HDMI is plugged into the HDMI sink via HDMI/EDID handshake. SRAM EDID will need to be overwritten prior to plugging in the HDMI cable.

    For further assistance, I attached a EDID usage guide for FPD-Link devices for reference. 

    8267.Using EDID in FPD-Link Devices (3).pdf

    Regards, 

    Logan

  • 0 in reply to Logan Cummins
    Prodigy 160 points

    hello Logan, 

    From the document you provide, when MODE_SEL0 strap low=0, to look for remote EDID, if none found, use internal EDID SRAM.

    I think the remote EDID is deserelizer side EDID, I only test with one DS90UB949 board and no deserializer board/chip, so I think remote EDID would not be found. the PC side/HDMI source will use internal EDID SRAM.

    From the PC side/HDMI source, I can get the EDID(1) and display property.

    With ALP script, I read back the EDID(2) from internal SRAM of DS90UB949.

    The EDID(2) is the same as internal pre-programmed EDID from DS90UB949, but totally different from EDID(1).

    My DS90UB949 board has an external local EEPROM.

    the test result shows PC Side/HDMI source uses DS90UB949 external local EEPROM data as EDID data.

    the test result is different from your document.

    I would like to know, when MODE_SEL0 strap low=0, what the PC side/HDMI source will  get EDID data from? DS90UB949 internal EDID SRAM or on-board external local EEPROM?