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OMAP 3525 GPIO problems

Kazemir
Prodigy 80 points
Other Parts Discussed in Thread: OMAP3525

We are working on a relatively new OMAP3525 design, and have tested most things on the board.  We are having some troubles with a few of the GPIO's (while we already got the more complicated stuff working, it is the simple IO's that are causing us the most grief!).

Here is a list of our GPIO's, and the corresponding BGA ball.

Inputs only:

F27 - GPIO_78

G25 – GPIO_86

D28 – GPIO_66

N28 – GPIO_120

M27 – GPIO_121

N27 – GPIO_122

N26 – GPIO_123

N25 – GPIO_124

P28 – GPIO_125

N8 – GPIO_58

 

Outputs only:

AB27 – GPIO_83

AA28 – GPIO_84

AA27 – GPIO_85 **

H27 – GPIO_87

H26 – GPIO_88

AC28 – GPIO_93 **

D27 – GPIO_68

E27 – GPIO_69

P27 – GPIO_126

K8 – GPIO_64

 

IO’s:

AD28 – GPIO_80

AD27 – GPIO_81 **

 

We have tested, and all of these work, except for these three: GPIO_85, GPIO_93 and GPIO_81.  We have spent several days looking into this, and we feel we have eliminated most of the obvious reasons (short on board, line being driven by two sources, power rails, register settings etc).  We have also confirmed that we get the same results on two different boards (which helps to eliminate a solder glitch as a problem).

 

Is there anything special about these three pins?  Any extra register settings that we should be aware of?

Thanks for any ideas/feedback.

Steve

  • 0
    Intellectual 885 points

    In general, if/when GPIO-s are shared with module pins (example GPIO_83 and SDI), the power for the GPIO comes from the power pins for that specific module.

     

    To enable the GPIO pins listed below, they need to draw power from the power rail for the module that they belong to in the alternate mode. In this specific case I think that VDSS_SDI and VSS_SDI need to be applied to activate these GPIO-s.

  • 0 in reply to Epic Vancouver
    Prodigy 80 points

    Thanks for the tip...however, we have looked at this.  With the case of GPIO_83, the SDI power is applied, as is evidenced by GPIO_80, 83, 84 all work properly.  I believe these are powered by the same rail.  GPIO_81 and GPIO_85 do not work, and they too are powered by this rail.  So we have some that do work, and some that don't work off of the same rail.

  • 0 in reply to Kazemir
    Prodigy 80 points

    Got gpio85 and gpio93 working.  Turns out that the power rail for these MUST be applied on startup for these pins to operate properly.  These were being powered up by the VDD_PLL2 rail, which came up later than the VIO_1V8 rail.  I jumpered these two power pins (AE27 and AG21) to the main IO rail, and they now operate properly.  This is strange, as other pins, off the same rail worked both ways (gpio83 for example).

    Now we are left with one io not working, gpio81.  Whereas gpio80 works fine (same power rail).

  • 0 in reply to Kazemir
    TI__Intellectual 1110 points

    Steve,

    GPIO_81 is a slightly different animal than GPIO_83, as it is muxed with the SDI_LOCK signal before going into the GPIO3 module (see figure 24-4). It will behave more like GPIO_80.

    Please review table 24-5 for the settings of the config mode (mode 4) and the PER power (Peripheral power - see PRCM module) as mentioned in notes [2] and [3]. Also note the register settings in paragraph 4.8.5.2 Wakeup Dependencies of the TRM which may apply depending on the way you intend to use GPIO_81.

    Regards