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Using GPIO 120-129 on OMAP3530

Rick Ball
Prodigy 185 points

Other Parts Discussed in Thread: TPS65920

I'm trying to use GPIO122 as a reset line for an external FPGA - I found the wiki article about the special considerations for GPIO 120-129, but I can't figure out how to get the companion power chip (in my case, the TPS65920) to set the MMC rail (MMC1_VDDS) to the required voltage (right now, it measures about 300mV).  I believe that the I2C interface between the OMAP and the power chip is handled exclusively by the OMAP, with no external software required?  So maybe there's a bit in an OMAP register somewhere (or maybe an external pull option?) to get the MMC voltage rail turned on?

  • 0
    TI__Genius 15100 points

    Hi,

    If you are asking how to set the VMMC on TPS65920 then here are the registers you will have to modify on TPS65920 using the correct I2C command.

    Please look at the following registers in the reference manual:

    VMMC1_DEV_GRP, the dev_group value should be non zero based on what your system is confirgured for. 

    VMMC1_DEDICATED[VSEL] - This bit should be set for the proper value you require.

    I dont have your schematics so I dont know which VMMC pin on TPS65920 is connected to OMAP. Based on the baove information you should be able to turn ON the VMMC LDO.

    Hope this helps.

  • 0 in reply to Gandhar Dighe
    Expert 1385 points

    If there was a resolution to this I'm interested in hearing it.

    I've tried setting VMMC1_DEV_GRP and VMMC1_DEDICATED in twl4030_usb_ldo_init.  I'm a bit puzzled by the meaning of "device group" P1/P2/P3 though.

    I'm also not sure how that relates to the  regulator_init_data struct.

     

    For reference: I'm using gpio 120-123 only.  I have set PBIASLITEVMODE0 and WRDNZ0, and I can read the gpio input values as 0/1 correctly.  However, when measuring the voltage level corresponding to the "1" signal it's at ~0.9V (expected: 1.8V).  There is no pull-up or pull-down set for the gpio inputs.  The "1" is pulled to 1.8V through a 10kohm resistor.

    (Before I set PBIASLITEVMODE0 and WRDNZ0, the voltage levels were the same, but were always interpreted as 0 since it used 3.0 V logic.)

     

    Thanks,

    Orjan