Read GPIO problem
#1
I use Pine64 A64-DB-Rev B board and Debian Jessie.

I need read some GPIO pins (69 and 233 on RPI connector) using sysfs. I use pullup resistors (10k) to 3.3v. Measure voltage on these pins. I get 3 v.
Set direction to 'in'.
But, reading /sys/class/gpio/gpioXX/value i always got 0 !

If switch direction to out, then back to in, reading get 1 ! 

Simple script to test:

Code:
#!/bin/sh

SYSFSDIR=/sys/class/gpio
DOOR_PIN=69
UPLVLPIN=233

setup(){
   if [ ! -d $SYSFSDIR/gpio$1 ] ; then
       echo $1 > $SYSFSDIR/export
   fi
   # If comment out these 2 lines - always read 0 !
   echo 'out' > $SYSFSDIR/gpio$1/direction
   echo 'in' > $SYSFSDIR/gpio$1/direction
}

gpio_read(){
   cat $SYSFSDIR/gpio$1/value
}

setup $DOOR_PIN
setup $UPLVLPIN

case "$1" in
   door)
       gpio_read $DOOR_PIN
       ;;
   uplevel)
       gpio_read $UPLVLPIN
       ;;
   *)
       usage
       ;;
esac

PS: Sorry for my bad english, my native language is Russian Wink
  Reply


Messages In This Thread
Read GPIO problem - by shworker - 02-21-2017, 04:00 AM
RE: Read GPIO problem - by Techsensei - 02-21-2017, 06:41 AM
RE: Read GPIO problem - by shworker - 02-21-2017, 08:58 AM
RE: Read GPIO problem - by MarkHaysHarris777 - 02-22-2017, 04:23 AM
RE: Read GPIO problem - by aromring - 08-05-2017, 09:59 PM
RE: Read GPIO problem - by MarkHaysHarris777 - 08-05-2017, 10:24 PM
RE: Read GPIO problem - by pfeerick - 08-06-2017, 01:33 AM
RE: Read GPIO problem - by MarkHaysHarris777 - 08-06-2017, 10:38 AM
RE: Read GPIO problem - by pfeerick - 08-07-2017, 12:11 AM
RE: Read GPIO problem - by MarkHaysHarris777 - 08-07-2017, 07:21 AM
RE: Read GPIO problem - by pfeerick - 08-07-2017, 07:21 PM
RE: Read GPIO problem - by MarkHaysHarris777 - 08-07-2017, 11:10 PM
RE: Read GPIO problem - by pfeerick - 08-08-2017, 06:20 PM
RE: Read GPIO problem - by MarkHaysHarris777 - 08-15-2017, 02:24 AM
RE: Read GPIO problem - by martinayotte - 08-17-2017, 01:21 PM

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