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DS90UB921-Q1: test pattern no display

Part Number: DS90UB921-Q1

Dear TI Team:

  I'm trying to use the internal test pattern generator to test the connection between DS90UB921 and DS90UB928(as follow).

  The Display only supports 44MHz, 1152x576@60fps.

I try to test pattern from ds90ub921, but it can't display.

1. My test code is follow. Is it any wrong? or can I test pattern from ds90ub928?

    i2cset -f -y 16 0x0c 0x66 0x03
    i2cset -f -y 16 0x0c 0x67 0x05
    i2cset -f -y 16 0x0c 0x66 0x07
    i2cset -f -y 16 0x0c 0x67 0x80
    i2cset -f -y 16 0x0c 0x66 0x08
    i2cset -f -y 16 0x0c 0x67 0x04
    i2cset -f -y 16 0x0c 0x66 0x09
    i2cset -f -y 16 0x0c 0x67 0x24
    i2cset -f -y 16 0x0c 0x66 0x04
    i2cset -f -y 16 0x0c 0x67 0x80
    i2cset -f -y 16 0x0c 0x66 0x05
    i2cset -f -y 16 0x0c 0x67 0x04
    i2cset -f -y 16 0x0c 0x66 0x06
    i2cset -f -y 16 0x0c 0x67 0x24
    i2cset -f -y 16 0x0c 0x66 0x0C
    i2cset -f -y 16 0x0c 0x67 0x20
    i2cset -f -y 16 0x0c 0x66 0x0D
    i2cset -f -y 16 0x0c 0x67 0x06
    i2cset -f -y 16 0x0c 0x66 0x0A
    i2cset -f -y 16 0x0c 0x67 0x08
    i2cset -f -y 16 0x0c 0x66 0x0B
    i2cset -f -y 16 0x0c 0x67 0x08
    i2cset -f -y 16 0x0c 0x66 0x0E
    i2cset -f -y 16 0x0c 0x67 0x03
    i2cset -f -y 16 0x0c 0x65 0x03
    i2cset -f -y 16 0x0c 0x64 0x11

2. Refer to Exploring the Int Test Pattern Generation Feature of FPD[1]Link III IVI Devices.pdf, Table 3-9. Pattern Generator Clock Divider N Configuration (PGCDC1),

   clock = 200Mhz / N

  How to set 44Mhz ?


  • Hi,

    I believe you are programming the test pattern correctly, however there may be an issue with the range your display supports. The closest the 200MHz clock can get to 44MHz is 40MHz using an N value of 5. Since the 200MHz clock itself can be anywhere from 140MHz to 260MHz, this 40MHz pclk can actually range from 28MHz to 52 MHz, with a nominal value of 40MHz. The display you are using may not be able to handle this wide range.

    If using the pattern generator with internal timing on this device, it is recommended to use an external, more accurate pixel clock. This is is allowed in register 0x65[3].



  • Dear Ben,

      Yes. using external timing(44MHz), and set restster 0x65[3], pattern display.

      Thanks very much!