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GPIOs as INPUTS on AM3874

Anonymous Developer
Expert 1275 points
Other Parts Discussed in Thread: AM3874

Hi,

Are there any problem setting some pins as inputs in am3874? To be more exact, we are having problems getting

inputs from the next pins.

PINCNTL63 - GP1[8]

PINCNTL64 - GP1[9]

PINCNTL65 - GP1[10]

PINCNTL173 - GP0[27]

PINCNTL228 - GP3[20]

From /sys/kernel/debug/omap_mux I can see the current value for these pins:

0xE0080 - Pull up enabled, mode 0x80

0xE0080 - Pull up enabled, mode 0x80

0xE0080 - Pull up enabled, mode 0x80

0x60080 - Pull up enabled, mode 0x80

0x60080 - Pull up enabled, mode 0x80

Where are seeing always an '1' with a pushbutton connected to GND, and with the scope we are seeing around 2.2V on the GP1[8], GP1[9] and GP1[10].

Regards,

Jorge

  • 0
    Expert 1275 points

    Hi,

    I've found half the solution in this link:

    http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/153934.aspx

    and in the new datasheet (sprugz7d.pdf) 3.1.2.2 Special Muxing of GPIO1[7:10] Signals section.

    Now I'm able to read the microswitches attached to GP1[7-10], but I have a curious behavior. When I changed GP1[7] changes the GP1[8] value too that I read. I can change GP1[8] without affecting GP1[7] value read. The other pair GP1[9] and GP1[10] do the same.

    Any hint is welcome!

    Regards,

    Jorge




  • 0 in reply to Anonymous Developer
    Expert 1275 points

    Jorge Fernandez said:

    Hi,

    I've found half the solution in this link:

    http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/153934.aspx

    and in the new datasheet (sprugz7d.pdf) 3.1.2.2 Special Muxing of GPIO1[7:10] Signals section.

    Now I'm able to read the microswitches attached to GP1[7-10], but I have a curious behavior. When I changed GP1[7] changes the GP1[8] value too that I read. I can change GP1[8] without affecting GP1[7] value read. The other pair GP1[9] and GP1[10] do the same.

    Any hint is welcome!

    Regards,

    Jorge




    External pull-up resistors to every GP1[7] to GP1[10] solves the problem! Internal pull-up doesn't work the same way other GPIOs

    Thanks!