GPIO 


http://www.armbedded.eu/node/258

echo 93 > /sys/class/gpio/export

You decide whether a pin is an input or an output by writing in/out to /sys/class/gpio/gpio[ID]/direction.

A GPIO's value can be read or set by accessing the file /sys/class/gpio/gpio[ID]/value.


 PB29:

echo 93 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio93/direction
echo 0 > /sys/class/gpio/gpio93/value



pinout p19


*((unsigned long *) (map_base + (PIOB_SODR & MAP_MASK))) = PIO_B27;



http://armbedded.org/node/309
Hi,

in Linux there is some kind of generic GPIO handling.

First you need to know the Linux internal GPIO number of the pin to use. Here some example to do that with PA26 (Buzzer). In arch/arm/mach-at91/include/mach/gpio.h you can find the pin definitions for the at91. Here PA26 is defined as

#define AT91_PIN_PA26 (PIN_BASE + 0x00 + 26)

PIN_BASE is 32 (some grep trough the sources will help).

so the Linux internal pin number of PA26 is 32+26=58.

Login into your board and cd to /sys/class/gpio. Then do a "echo 58 > export" here. This will export the PA26 gpio line from kernel space to user land. Then cd into the new directory gpio58. Here you will find the gpio pin control items. Do an "echo out > direction" to configure the pin as output. Now it can be altered by "echo 1 > value" and "echo 0 > value" (some click noise is made then by the buzzer).
========================================================
buzzer PA26
echo 58 > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio58/direction
echo 0 > /sys/class/gpio/gpio58/value
echo 1 > /sys/class/gpio/gpio58/value
========================================================





http://armbedded.org/node/420

Tried power saving
http://www.armbedded.eu/node/372

echo "" > /sys/class/rtc/rtc0/wakealarm
echo "+20" > /sys/class/rtc/rtc0/wakealarm
echo mem > /sys/power/state

1) works with NanosG20 and LogitechC510 webcam. Power use 0 W from mains.

2) Does not work with Huavei E1750 surf stick. Power consumed during power down = 1 W.

3) Does not work with RTL8187 stick. Power consumed with power down = 1.3W.

May be there is still some software method?
or I could try in hardware to switch off USB 5 V power with GPIO and external transistor.



You can toggle pin PA27 to switch off the 5V supply for USB (low is on, high is off). You can use this method to do it: http://armbedded.eu/node/258

Thanks a lot for supprt! Very smart feature! Will print out and study Nanos schematics.

This controls USB power:
echo 59 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio59/direction
echo 0 > /sys/class/gpio/gpio59/value  # +5V on
echo 1 > /sys/class/gpio/gpio59/value # +5V off

The value is not preserved after restart, but it is not a problem to set it every time.


-----------------------------------------------------------
connecting PIR motion detector to pin 14 of X11

X11
pin10 GND
pin12 +5V
pin14 PB14


64+14=78

echo 78 > /sys/class/gpio/export
echo "in" > /sys/class/gpio/gpio78/direction
cat  /sys/class/gpio/gpio78/value

input works