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TMS320F2808 I/O High impedance

Maxime Tardif
Prodigy 20 points

Other Parts Discussed in Thread: TMS320F2808

Hello,

I need to configure a I/O in High impendance, but I can not find how!

GPAMUX, GPADIR, GPAQSEL1, GPAQSEL2, GPACTRL.

I have look this register, but no solution.

It's this possible to do.

If we take a look at the General Data sheet of the TMS320F2808, at page 23, All the GPIO seem to be available to be set High impedance. 

GPIO0 General purpose input/output 0 (I/O/Z) (4)
EPWM1A 47 K8 Enhanced PWM1 Output A and HRPWM channel (O) - -
- -
GPIO1 General purpose input/output 1 (I/O/Z)(4)
EPWM1B 44 K7 Enhanced PWM1 Output B (O) SPISIMOD SPI-D slave in, master out (I/O) (not available on 2801, 2802)
- -
GPIO2 General purpose input/output 2 (I/O/Z)(4)
EPWM2A 45 J7 Enhanced PWM2 Output A and HRPWM channel (O) - -
- -
GPIO3 General purpose input/output 3 (I/O/Z)(4)
EPWM2B 48 J8 Enhanced PWM2 Output B (O) SPISOMID SPI-D slave out, master in (I/O) (not available on 2801

etc..

Solution ??

Thank for any clue.

Maxime Tardif

 

  • 0
    Expert 2355 points

    First of all see Section 4 of the Sys Ctrl and Ints Guide:

    http://focus.ti.com/lit/ug/spru712g/spru712g.pdf

    This covers GPIO on the F2808.

    I believe, in order for a pin to be guaranteed Hi-Z the following needs to be done (someone correct me if I am wrong):

    1) Change GPAMUX bits to ensure the GPIO is a GPIO not a peripheral.

    2) Change GPADIR bits to set the GPIO as an input.

    3) Set GPAPUD bits to ensure that the internal pull up is disabled.

    By default, on reset, steps 1 and 2 should be done for you (i.e. pins are default input on reset).  All you should really need to do is ensure the pull-up is disabled.

    Tim