pwm: C: Add PWM example

Signed-off-by: Andre Riesco <andre.riesco@toradex.com>

pwm/C/pwmC/Makefile

@@ -1,5 +1,5 @@
 # tool macros
-CC := g++
+CC := gcc
 CCFLAGS := -Iincludes/
 DBGFLAGS := -g
 LDFLAGS :=

pwm/C/pwmC/docker-compose.yml

@@ -7,9 +7,13 @@ services:
     image: ${LOCAL_REGISTRY}:5002/pwmc-debug:${TAG}
     ports:
       - 2230:2230
+    volumes:
+      - /sys/class/pwm/pwmchip0:/sys/class/pwm/pwmchip0
 
   pwmc:
     build:
       context: .
       dockerfile: Dockerfile
     image: ${DOCKER_LOGIN}/pwmc:${TAG}
+    volumes:
+      - /sys/class/pwm/pwmchip0:/sys/class/pwm/pwmchip0

pwm/C/pwmC/src/main.c

@@ -0,0 +1,59 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "pwm_utils.h"
+
+#define PERIOD 1000000000
+#define DUTY_CYCLE 500000000
+#define POLARITY "normal"
+
+int main(int argc, char **argv)
+{
+    if ( pwm_exists("/sys/class/pwm/pwmchip0/pwm0/") < 0 ) {
+        if( pwm_write_val("/sys/class/pwm/pwmchip0/export", 0) < 0)
+        {
+            printf("failed to export \n");
+            exit(EXIT_FAILURE);
+        }
+    }    
+
+    if( pwm_write_val("/sys/class/pwm/pwmchip0/pwm0/period", PERIOD) < 0)
+    {
+        printf("failed to set period\n");
+        exit(EXIT_FAILURE);    
+    }
+
+    if( pwm_write_val("/sys/class/pwm/pwmchip0/pwm0/duty_cycle", DUTY_CYCLE) < 0)
+    {
+        printf("failed to set duty cycle\n");
+        exit(EXIT_FAILURE);    
+    }    
+
+    if( pwm_write_str("/sys/class/pwm/pwmchip0/pwm0/polarity", POLARITY) < 0)
+    {
+        printf("failed to set polarity\n");            
+        exit(EXIT_FAILURE);    
+    }
+
+    if( pwm_write_val("/sys/class/pwm/pwmchip0/pwm0/enable", 1) < 0)
+    {
+        printf("failed to enable pwm\n");
+        exit(EXIT_FAILURE);
+    }    
+
+    char d_cycle[10]={0};    
+    if( pwm_read("/sys/class/pwm/pwmchip0/pwm0/duty_cycle", d_cycle, 9) < 0)
+        printf("unable to read duty cycle\n");
+    else
+        printf("duty cycle is %s\n",d_cycle);
+
+    char polarity[10]={0};
+    if( pwm_read("/sys/class/pwm/pwmchip0/pwm0/polarity", polarity, 6) < 0)
+        printf("failed to read polarity\n");
+    else
+        printf("polarity is %s\n",polarity);
+
+    return 0;
+}

pwm/C/pwmC/src/pwm_utils.c

@@ -0,0 +1,101 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h> 
+#include <dirent.h>
+
+#include "pwm_utils.h"
+
+#define MAX_BUF 50
+
+int pwm_write_val(char *file, uint32_t val)
+{
+    int fd;
+    char buf[MAX_BUF]; 
+
+    fd = open(file, O_WRONLY);
+    if(fd < 0)
+    {
+        printf("Error Number % d\n", errno);  
+        perror("pwm");                  
+        return -1;
+    }        
+    if( snprintf(buf, MAX_BUF, "%u", val) < 0)
+        goto failed; 
+
+    if( write(fd, buf, strlen(buf)) < 0)
+    {
+        printf("Error Number % d\n", errno);  
+        perror("pwm");                  
+        goto failed;
+    }
+
+    close(fd);    
+    return 0;
+
+failed:
+    close(fd);
+    return -1;
+}
+
+int pwm_write_str(char *file, char *val)
+{
+    int fd;
+
+    fd = open(file, O_WRONLY);
+    if(fd < 0)
+    {
+        printf("Error Number % d\n", errno);  
+        perror("pwm");
+        return -1;
+    }        
+    if( write(fd, val, strlen(val)) < 0)
+    {
+        printf("Error Number % d\n", errno);  
+        perror("pwm");                  
+        close(fd);
+        return -1;
+    }
+
+    close(fd); 
+    return 0;
+}
+
+int pwm_read(char *file, char *val, uint8_t size)
+{
+    int fd;
+
+    fd = open(file, O_RDONLY);
+    if(fd < 0)
+    {
+        printf("Error Number % d\n", errno);  
+        perror("pwm");                          
+        return -1;
+    }
+    if( read(fd, val, size) < 0)
+    {
+        printf("Error Number % d\n", errno);  
+        perror("pwm");                          
+        close(fd);
+        return -1;    
+    }
+
+    close(fd);     
+    return 0;
+}
+
+int pwm_exists(char *file) {
+
+    DIR* fd = opendir(file);
+    int exists;
+    if(fd)
+    {     
+        exists = 0;                      
+    } else {
+        exists = -1;
+    }
+    closedir(fd);  
+    return exists;
+}

pwm/C/pwmC/src/pwm_utils.h

@@ -0,0 +1,9 @@
+#ifndef __PWM_UTILS_H__
+#define __PWM_UTILS_H__
+
+int pwm_write_val(char *file, uint32_t val);
+int pwm_write_str(char *file, char *val);
+int pwm_read(char *file, char *val, uint8_t size);
+int pwm_exists(char *file);
+
+#endif