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DS90UB921-Q1: USE I2S CLK as GPIO in 921

Amelie Zheng
Genius 10865 points
Part Number: DS90UB921-Q1

Hi Team

Just want to simplify the question.

When using 921/948, could customer use I2S_CLK to transfer PWM from 921 to 948? If yes, how to configure?

Thanks!

*******original *************

At present, in ti949->ti948, pwm signals can be transparently transmitted through gpio3, but because we have three screens, we use ti949, ti947, and ti921 respectively, but the gpio port of ti921 is occupied, only the I2S_CLK pin can be used, considering the hardware design For uniformity and future mass production, only the I2S_CLK pin can be used to transparently transmit the pwm signal, but there are some problems currently, so please give me some advice:
Set ti949 register: 0x12->0x0b 0x1a->0x09
Set ti948 register: 0x21->0x09
I now set my PWM to 1k and 1M, and it can’t be transmitted transparently, and the I2S_CLK of ti948 has a 3.072M clock.
Could you please give any advice about this?

  • 0
    TI__Mastermind 25955 points

    Hi Amelie,

    A block diagram would be very helpful here.

    Trying to understand the topology of your system.  You mentioned 3 displays, and 3 different serializers.  Are all 3 deserializers 948?

    on 921, the i2s_clk pin may be optionally used with GPO_REG8.

    on 947, the i2s_clk pin may be optionally used with GPIO_REG8.

    on 949, the i2s_clk pin may be optionally used with GPIO_REG8, as shown in table 3 (page 22 of the datasheet).

    GPIO_REG8 is a register only GPIO.  It can be set high or low by a local write to register 0x11, or read locally at 0x1D.  Please make sure GPIO_REG8 is not set as it will override the I2S_CLK.

    The bit clock (I2S_CLK) supports frequencies between 1MHz and the lesser of CLK/2 up to 13 MHz.

    What is the setting of bridge_cfg 0x54?

    Please try setting 0x1a -> 0x08 since forward channel mode is being used.

    Sincerely,
    Bryan Kahler

  • 0 in reply to Bryan Kahler
    TI__Genius 10865 points

    Hi Bryan,

    Thanks for your reply. Customer will use three different solution in their different design. However, they would like to use the same pin I2S-CLK to transfer PWM signal in all these three solution.

    The question is when using 921/948, could customer use I2S_CLK to transfer PWM from 921 to 948?

    In my understand, I2S_CLK only could change the frequency, could it could the duty cycle? If it can't change the duty cycle, it is not suitable for transferring the PWM signal.

    If I2S_CLK could change the frequency and duty cycle, how to configure it?

  • 0 in reply to Amelie Zheng
    TI__Mastermind 25955 points

    Hi Amelie,

    Please use GPIO[0:3] for a PWM.

    Sincerely,
    Bryan Kahler