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@llbit
Last active September 5, 2024 07:42
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Raspberry Pi GPIO pins via C
// Compile with $ gcc water.c -o water
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
// Pin modes:
#define INPUT (0)
#define OUTPUT (1)
#define LOW (0)
#define HIGH (1)
typedef struct {
int pin;
char* fn;
} pin_t;
static pin_t pinopen(int pin, int mode);
static void pinclose(pin_t pin);
static void pinwrite(pin_t pin, int value);
static int pinread(pin_t pin);
int main(int argc, char** argv)
{
int time = 0;
if (argc > 1) {
time = atoi(argv[1]);
}
if (time == 0) {
printf("Usage: water <SECONDS>\n");
printf("Runs the water pump for the specified number of seconds.\n");
printf("The pump control signal must be connected to GPIO17!\n");
return 1;
}
// Use GPIO17.
pin_t waterpin = pinopen(17, OUTPUT);
pinwrite(waterpin, HIGH);
sleep(time);
pinwrite(waterpin, LOW);
pinclose(waterpin);
return 0;
}
pin_t pinopen(int pin, int mode)
{
char* pinfn = malloc(1024);
char dirfn[1024];
FILE* dir = NULL;
FILE* fp = fopen("/sys/class/gpio/export", "w");
fprintf(fp, "%d", pin);
fclose(fp);
snprintf(dirfn, 1024, "/sys/class/gpio/gpio%d/direction", pin);
snprintf(pinfn, 1024, "/sys/class/gpio/gpio%d/value", pin);
while (dir == NULL) {
dir = fopen(dirfn, "w");
}
if (mode == INPUT) {
fprintf(dir, "in");
} else {
fprintf(dir, "out");
}
fclose(dir);
return (pin_t) { pin, pinfn };
}
void pinclose(pin_t pin)
{
FILE* fp = fopen("/sys/class/gpio/unexport", "w");
fprintf(fp, "%d", pin.pin);
fclose(fp);
free(pin.fn);
}
void pinwrite(pin_t pin, int value)
{
FILE* fp = fopen(pin.fn, "w");
if (value == LOW) {
fprintf(fp, "0");
} else {
fprintf(fp, "1");
}
fclose(fp);
}
int pinread(pin_t pin)
{
char buf[2];
FILE* fp = fopen(pin.fn, "r");
size_t read = fread(buf, 1, 2, fp);
fclose(fp);
if (read != 2) {
return -1;
} else {
return (buf[0] == '1') ? HIGH : LOW;
}
}
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