V1: switch.c

V1/switch.c

@@ -0,0 +1,100 @@
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#define BASEPATH "/sys/class/gpio/"
+#define GPIO_FOLDER "gpio%s/"
+
+#define PIN_BUTTON "17"
+#define PIN_LED "18"
+
+#define LED_ON 0
+#define LED_OFF 1
+
+#define BUTTON_PRESSED 0
+#define BUTTON_RELEASED 1
+
+void writeFile(char *filename, char *buffer, size_t count)
+{
+    int fd = open(filename, O_WRONLY);
+    write(fd, buffer, count);
+    close(fd);
+}
+
+void registerPin(char *pin)
+{
+    writeFile(BASEPATH "export", pin, strlen(pin));
+}
+
+void freePin(char *pin)
+{
+    writeFile(BASEPATH "unexport", pin, strlen(pin));
+}
+
+void registerInput(char *pin)
+{
+    registerPin(pin);
+    char path[50];
+    sprintf(path, BASEPATH GPIO_FOLDER "direction", pin);
+    writeFile(path, "in", 2);
+}
+
+void registerOutput(char *pin)
+{
+    registerPin(pin);
+    char path[50];
+    sprintf(path, BASEPATH GPIO_FOLDER "direction", pin);
+    writeFile(path, "out", 3);
+}
+
+int readInput(char *pin)
+{
+    char path[50];
+    int state;
+    sprintf(path, BASEPATH GPIO_FOLDER "value", pin);
+    FILE *fd = fopen(path, "r");
+    fscanf(fd, "%i", &state);
+    fclose(fd);
+    return state;
+}
+
+void writeOutput(char *pin, int state)
+{
+    char path[50];
+    sprintf(path, BASEPATH GPIO_FOLDER "value", pin);
+    FILE *fd = fopen(path, "w");
+    fprintf(fd, "%i", state);
+    fclose(fd);
+}
+
+int main()
+{
+    struct timespec sleeptime, sleepremain;
+    int oldstate = BUTTON_PRESSED;
+    int state;
+    int count = 0;
+    registerInput(PIN_BUTTON);
+    registerOutput(PIN_LED);
+    sleeptime.tv_sec = 0;
+    sleeptime.tv_nsec = 1000000;
+    nanosleep(&sleeptime, &sleepremain);
+    while (1)
+    {
+        state = readInput(PIN_BUTTON);
+        if (state == BUTTON_PRESSED && oldstate == BUTTON_RELEASED)
+        {
+            count++;
+            printf("Number of button pushes: %i\n", count);
+        }
+
+        if (state == BUTTON_PRESSED)
+            writeOutput(PIN_LED, LED_ON);
+        else
+            writeOutput(PIN_LED, LED_OFF);
+
+        oldstate = state;
+        nanosleep(&sleeptime, &sleepremain);
+    }
+}