Xenomai:Blinking LEDs

This tutorial explains how to create a simple Xenomai application. This application will blink the APF9328DevFull user LED (connected to pin 31 of i.MXL portD; on the APF27 you would use pin 14 of portF).

Application code

$ mkdir xeno_led
$ vim xeno_led/blink.c

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <signal.h>
#include <sys/mman.h>

#include <native/task.h>
#include <native/timer.h>

#define TIMESLEEP 1000000000 /* 1 sec */
#define LED "/dev/gpio/PD31" /* APF9328 */
#define LED "/dev/gpio/PF14" /* APF27 */

RT_TASK blink_task;
int fd;

void blink(void *arg __attribute__((__unused__)))
{
    int iomask = 0x00;
  
    rt_task_set_periodic(NULL, TM_NOW, TIMESLEEP);
  
    while(1) {
        rt_task_wait_period(NULL);
        write(fd,&iomask,sizeof(iomask));
        iomask ^= 1;
    }
}

void catch_signal() {}

int main(void)
{  
    signal(SIGTERM, catch_signal);
    signal(SIGINT, catch_signal);
  
    /* Avoids memory swapping for this program */
    mlockall(MCL_CURRENT|MCL_FUTURE);

    /* led device opening */
    if ((fd = open(LED, O_WRONLY)) < 0) {
        printf("Open error on %s\n",LED);
        exit(0);
    }
    /* Task Creation */
    rt_task_create(&blink_task, "blinkLed", 0, 99, 0);  
    rt_task_start(&blink_task, &blink, NULL);
    getchar();
    rt_task_delete(&blink_task);
    close(fd);

    return 0;
}

This source looks very like a classical Linux application with threads and nanosleep() function.
The only differences are on the task creation using Xenomai API:

• Create a new task with stksize stack size, prio level of priority and mode type of creation:

 int rt_task_create(RT_TASK * task, const char * name, int stksize, int prio, int mode)

• Launch the new task with entry function and cookie parameters:

 int rt_task_start (RT_TASK *task, void(*entry)(void *cookie), void *cookie)

• set for the task periodic, idate time for the first release (time in nanoseconds)

 int rt_task_set_periodic (RT_TASK *task, RTIME idate, RTIME period)

• To block the task during the previously set period:

 int rt_task_wait_period (unsigned long *overruns_r)

Makefile

The second step is to create a Makefile with specific Xenomai includes.

$ vim xeno_led/Makefile

###### CONFIGURATION ######
DEST_DIR=/tftpboot/local/bin
ARMADEUS_BASE_DIR=../
include $(ARMADEUS_BASE_DIR)/Makefile.in

XENO=$(ARMADEUS_ROOTFS_DIR)/usr/xenomai

CC:=$(ARMADEUS_TOOLCHAIN_PATH)/arm-linux-gcc
LD:=$(ARMADEUS_TOOLCHAIN_PATH)/arm-linux-ld
CXX:=$(ARMADEUS_TOOLCHAIN_PATH)/arm-linux-g++
AS:=$(ARMADEUS_TOOLCHAIN_PATH)/arm-linux-as
NM:=$(ARMADEUS_TOOLCHAIN_PATH)/arm-linux-nm
AR:=$(ARMADEUS_TOOLCHAIN_PATH)/arm-linux-ar
SIZE:=$(ARMADEUS_TOOLCHAIN_PATH)/arm-linux-size
OBJCOPY:=$(ARMADEUS_TOOLCHAIN_PATH)/arm-linux-objcopy

EXEC=blink_led_xeno_userspace

SRC= $(wildcard *.c)
OBJ= $(SRC:.c=.o)
CFLAGS=-g -W -Wall -I$(XENO)/include -I$(XENO)/include/native  -I$(XENO)/include/rtdm -D_GNU_SOURCE -D_REENTRANT
LDFLAGS=-L$(XENO)/lib -Xlinker -rpath $(XENO)/lib -Xlinker $(XENO)/lib/libnative.a $(XENO)/lib/librtdm.a -lpthread -lnative -lrtdm

$(EXEC): $(OBJ)
	$(CC) -o $@ $^ $(LDFLAGS)

$(OBJ): $(SRC)
	$(CC) $(CFLAGS) -o $@ -c $<

all: $(EXEC)

clean:
	rm -rf $(OBJ)
	rm -rf $(EXEC)
	rm -f *.c~ *.h~ Makefile~

install: $(EXEC)
	@mkdir -p $(DEST_DIR)/$(EXEC)
	echo "$(EXEC):native:!./$(EXEC);popall:control_c" > $(DEST_DIR)/$(EXEC)/.runinfo
	cp -f $(EXEC) $(DEST_DIR)/$(EXEC)

mrproper: clean
	rm -rf $(DEST_DIR)/$(EXEC)

.PHONY: all install clean mrproper

• ARMADEUS_BASE_DIR: needs to be adapted to the correct path where the Armadeus SDK is installed, relatively to your example dir or as an absolute path.
• DEST_DIR: directory where the executables will be installed when doing make install. Here it assumes you used an NFS exported dir /tftpboot/local, mount as /usr/local on the board.

Compilation, installation and run

$ make -C xeno_led

• If you setup the NFS as indicated above, you can install the application on your board with:

$ make install -C xeno_led

• Otherwise you can install the executable to your board (through TFTP for example):

$ make install -C xeno_led/ DEST_DIR=/tftpboot

# mkdir -p /usr/local/bin/blink_led_xeno_userspace
# tftp -g -r blink_led_xeno_userspace/blink_led_xeno_userspace -l /usr/local/bin/blink_led_xeno_userspace/blink_led_xeno_userspace 192.168.1.2
# tftp -g -r blink_led_xeno_userspace/.runinfo -l /usr/local/bin/blink_led_xeno_userspace/.runinfo 192.168.1.2
# chmod a+x /usr/local/bin/blink_led_xeno_userspace/blink_led_xeno_userspace

Running

• GPIO driver should be loaded:

# loadgpio.sh

• And you should be able to blink the LED from command line following these instructions
• Then, you must change directory to /usr/local/bin and type :

# xeno-load blink_led_xeno_userspace

Links

• Xenomai installation instructions
• Using Armadeus Xenomai custom examples
• Xenomai API page