GPIO Driver
From ArmadeusWiki
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Warning: This article describe the method to use gpio with armadeus version < 4.0. To use gpio on armadeus version 4.0 or more see GPIOlib |
On this page, you will find all the informations needed to use the Armadeus GPIO driver.
Contents
Installation
Compilation
Since Armadeus-3.0 release, gpio driver is compiled and installed by default in rootfs. See Talk:GPIO_Driver to know how.
You have 2 modules:
- gpio: this is the main driver. It should be loaded first and will allow you to easily control GPIO pins from user space,
- ppdev: this is an extension driver to add PPDEV emulation to gpio.ko. This way you will be able to emulate a standard parallel port on one GPIO port (to connect a textual LCD, for example).
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Note: The parallel port driver (ppdev) will only work on APF9328 based systems for now ! |
Loading driver
# /usr/bin/loadgpio.sh
or look inside this script if you want to manually enter the module parameters:
# modprobe gpio portB_init=0,0,0x00FFFF00,0,0,0,0,0,0x0FF00000,0,0,0,0,0,0,0x0FF00000
gpio module parameters are values for PORTA, PORTB, PORTC, PORTD configuration registers in following order:
DDIR, OCR1, OCR2, ICONFA1, ICONFA2, ICONFB1, ICONFB2, DR, GIUS, SSR, ICR1, ICR2, IMR, GPR, SWR, PUEN,
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Warning: If you don't know what these registers means, load the module without parameters !! |
Driver usage
As_devices
GPIO can be use with library AsDevices.
Directly with shell commands (through /proc & /dev filesystem)
GPIO driver is usable through its /proc interface:
- use /proc/drivers/gpio/portXmode to configure a pin as a gpio (with echo) and where X is your port name: A, B, C or D (E,F for apf27)
- use /proc/drivers/gpio/portXdir to read (with cat) or set (with echo) pin direction (where X is your port name)
- then use /proc/drivers/gpio/portX to read (with cat) or write (with echo) pin status
- /proc/drivers/gpio/portXirq: to configure GPIO as an interrupt (blocking read); 0-> no interrupt, 1-> rising edge, 2-> falling edge, 3-> both edges
- /proc/drivers/gpio/portXpullup: (de)activate i.MX internal pull-up for that GPIO
Examples
- Configure IO-Pin 31 of port A (LCD_OE_ACD on the APF27) as GPIO (not reversible):
# echo -n 10000000000000000000000000000000 > /proc/driver/gpio/portAmode
- See which IO-Pins of PortD are configured as inputs, and which one are outputs ('1' = output, '0' = input):
# cat /proc/driver/gpio/portDdir 01101100111100000110110011110000 pins order: [31...0] #
- Configure the IO-Pins 30, 28, 23, 22 and 21 of PortB as outputs ('1'), all others as inputs ('0'):
# echo -n 01010000111000000000000000000000 > /proc/driver/gpio/portBdir
- Read the status/values of the IOs of PortB:
# cat /proc/driver/gpio/portB 00000000000011111111000000000000 #
- Set bits 30, 28 and 23 of PortB to '1', all other outputs to '0': <-- DEPRECATED, use /dev/gpio/ instead !
# echo -n 01010000100000000000000000000000 > /proc/driver/gpio/portB
- Blinks the LED on APF9328DevFull (pin 31 of portD):
# cat /proc/driver/gpio/portDmode | sed "s/[0-1]\([0-1]\{31\}\)$/1\1/" > /proc/driver/gpio/portDmode
# cat /proc/driver/gpio/portDdir | sed "s/[0-1]\([0-1]\{31\}\)$/1\1/" > /proc/driver/gpio/portDdir
# echo -ne "\x00" > /dev/gpio/PD31
# echo -ne "\x01" > /dev/gpio/PD31
- Blinks the LED on APF27Dev (pin 14 of portF):
# cat /proc/driver/gpio/portFmode | sed "s/[0-1]\([0-1]\{14\}\)$/1\1/" > /proc/driver/gpio/portFmode
# cat /proc/driver/gpio/portFdir | sed "s/[0-1]\([0-1]\{14\}\)$/1\1/" > /proc/driver/gpio/portFdir
# echo -ne "\x01" > /dev/gpio/PF14
# echo -ne "\x00" > /dev/gpio/PF14
- Sets only bit 5 of portADir to 1:
# cat /proc/driver/gpio/portAdir | sed "s/[0-1]\([0-1]\{'''5'''\}\)$/'''1'''\1/" > /proc/driver/gpio/portAdir
- Sets only bit 5 of portADir to 0:
# cat /proc/driver/gpio/portAdir | sed "s/[0-1]\([0-1]\{'''5'''\}\)$/'''0'''\1/" > /proc/driver/gpio/portAdir
- You can put it in a shell function:
setbit()
{
PORT=$1
NB=$2
VAL=$3
cat $PORT | sed "s/[0-1]\([0-1]\{$NB\}\)$/$VAL\1/" > $PORT
}
# setbit /proc/driver/gpio/portAdir 5 0
- Blocking read on the PortD pin 0:
# cat /dev/gpio/PD0 | less
- A test script is available in target/test/ : test_gpio.sh
Directly from a C program with IOCTLs
There is another way to drive GPIO module: with IOCTLs on the right device node (full port).
ioctl() function is using flags to say what must be done:
- GPIORDDIRECTION for reading direction settings of the corresponding port
- GPIOWRDIRECTION for writing direction settings
- GPIORDDATA for reading data on the corresponding port
- GPIOWRDATA for writing data
- Etc...
There is a small C example in target/demos/gpio/ that will give you more explanation: blink_led.c
Directly with C program: /proc filesystem
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Note: For performance please use IOCTL instead (see above) |
After inserting the GPIO module, /proc entries are created in the
filesystem, and so it's possible to directly use some Linux standard functions
inside a C program, such as:
- fopen
- fwrite
- fread
- fclose
A little piece of code is the best way to understand quickly:
int i;
unsigned char dummy;
FILE *GPIO,*GPIODIR, *GPIOMODE;
char buffer[32];
char * bufferMode="00000000011111111000000000000000";
char * bufferDir= "00000000011111111000000000000000";
char * buffer1= "00000000000000011000000000000000";
char * buffer2= "00000000000001100000000000000000";
char * buffer3= "00000000000110000000000000000000";
char * buffer4= "00000000011000000000000000000000";
GPIOMODE = fopen("/proc/driver/gpio/portDmode","w");
setvbuf(GPIOMODE,buffer,_IONBF,32);
fwrite(bufferMode, sizeof(char), strlen(bufferMode), GPIOMODE);
fclose(GPIOMODE);
GPIODIR = fopen("/proc/driver/gpio/portDdir","w");
setvbuf(GPIODIR,buffer,_IONBF,32);
fwrite(bufferDir, sizeof(char), strlen(bufferDir), GPIODIR);
fclose(GPIODIR);
GPIO = fopen("/proc/driver/gpio/portD","w");
setvbuf(GPIO,buffer,_IONBF,32);
while(1) {
fwrite(buffer1, sizeof(char), strlen(buffer1), GPIO);
sleep(1);
fwrite(buffer2, sizeof(char), strlen(buffer2), GPIO);
sleep(1);
fwrite(buffer3, sizeof(char), strlen(buffer3), GPIO);
sleep(1);
fwrite(buffer4, sizeof(char), strlen(buffer4), GPIO);
sleep(1);
}
fclose(GPIO);
return (0);
