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OMAP3530 - 3V MMC outputs as GPIO

Philippe MAIRE
Intellectual 500 points
Other Parts Discussed in Thread: DM3730

Hi,

In my design I am using a 4 bit SD interface in 3V, with MMC1_DAT[7..4] as GPIO.

Can I put vdds_mmc1a at 3.3V to have 3.3V GPIOs ?

Thanks

Philippe

  • 0
    Intellectual 500 points

    Well, a bit of a monologue here... I've found the answer :-)

    TRM chapter 7.4.5.1 PBIAS Cells

    "With the appropriate configuration of the PBIAS cell, gpio120 through gpio129
    I/Os(MuxMode = 0x4) can operate in 3-V mode."

     

  • 0 in reply to Philippe MAIRE
    Prodigy 75 points

    Hi Phillippe,

    I am also working on doing this on the DM3730.  

    Following is the e-mail I dropped to my FAE.  If you have some extra info on specifically what needs to be configured and when, I would be highly appreciative.

     

    -----snip--------

    I am running into a problem using the TI DM3730 part.  We are trying to use GPIO ports 127 & 129 for normal 1.8V GPIO, but these ports are “extended-drain” I/O pins which require extra configuration of “PBIAS” circuitry, which selects between 1.8V and 3.0V output based on input voltage on the SIM_VDDS supply rail.  At this point I’ve done all the configuration the data sheet recommends, and I am still not able to use these pins as GPIO.  I am noting that the data sheet is not very clear on the use case I’m describing.

     

    My general configuration practice (testing with pin 129):

    (CONTROL_PBIAS_LITE[PBIASLITEPWRDNZ1] is 0 to start)

    ·         Set SIM_VDDS supply to 1.8V  (The signals are buried, so verifying this electrically this would be tough, but a step that may be necessary)

    ·         Set pin mux to output (no pullup/pulldown)

    ·         Set GPIO output enable for pin 129

    ·         Set GPIO output high for pin 129 (will light an LED when the pin is high)

    ·         Set CONTROL_PBIAS_LITE[PBIASLITEVMODE1] to 0

    ·         Set CONTROL_PBIAS_LITE[PBIASLITEPWRDNZ1] to 1

    ·         Set CONTROL_WKUP_CTRL[GPIO_IO_PWRDNZ] to 1  (not sure if this necessary but I have tested with and without this step)

     

    So far none of this has worked.  I have attempted to set the pin in “pull-up” state through the MUX register and notice that it lights the LED in this state but is not controllable by the normal GPIO registers. 

     

    Summary:  My goal is to have the pins 127 & 129 behave like any other GPIO (‘0’ causes a low state on the output, ‘1’ causes a high state (1.8V) on the output).  My problem is that they don’t behave that way and the MCU requires extra configuration to get them to.

     

  • 0 in reply to David Stude
    Prodigy 75 points

    Update:

    Just found a spot to measure my SIM_VDDS and it looks like that's not set correctly.  Looks like I need to address that first.  :)