add nix derivation for compiling with CMAKE

pin_control/src/pin_control.c

@@ -0,0 +1,104 @@
+#include <stdio.h>
+#include <gpiod.h>
+
+// https://docs.kernel.org/driver-api/gpio/using-gpio.html
+
+#define GPIO_CHIP "gpiochip0"
+
+struct gpiod_chip *chip;
+
+int init_gpio() {
+    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_chip_open_by_name.html
+    chip = gpiod_chip_open_by_name(GPIO_CHIP);
+    if (!chip) {
+        printf("Error opening GPIO chip");
+        return -1;
+    }
+    return 0;
+}
+
+void cleanup_gpio() {
+    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_chip_close.html
+    gpiod_chip_close(chip);
+}
+
+int set_pin_state(int pin, int state) {
+    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_chip_get_line.html
+    struct gpiod_line *line = gpiod_chip_get_line(chip, pin);   // this may need an offset
+    if (!line) {
+        printf("Error getting GPIO line");
+        return -1;
+    }
+
+    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_line_request_output.html
+    if (gpiod_line_request_output(line, "house-leds", state) < 0) {
+        printf("Error setting GPIO line direction");
+        gpiod_line_release(line);
+        return -1;
+    }
+
+    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_line_set_value.html
+    if (gpiod_line_set_value(line, state) < 0) {
+        printf("Error setting GPIO line value");
+        gpiod_line_release(line);
+        return -1;
+    }
+
+    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_line_release.html
+    gpiod_line_release(line);
+    return 0;
+}
+
+int turn_on_pin(int pin) {
+    return set_pin_state(pin, 1);
+}
+
+int turn_off_pin(int pin) {
+    return set_pin_state(pin, 0);
+}
+
+int turn_on_all_pins() {
+    for (int pin = 0; pin <= 5; pin++) {
+        if (turn_on_pin(pin) < 0)
+            return -1;
+    }
+    return 0;
+}
+
+int turn_off_all_pins() {
+    for (int pin = 0; pin <= 5; pin++) {
+        if (turn_off_pin(pin) < 0)
+            return -1;
+    }
+    return 0;
+}
+
+int button_presssed(int event, unsigned int pin, const struct timespec * timestamp, void *data) {
+    (void) event;
+    (void) timestamp;
+    * (int *) data = (int) pin;
+    return GPIOD_CTXLESS_EVENT_POLL_RET_STOP;
+}
+
+int wait_for_button_press(unsigned int pins[]) {
+    // https://www.lane-fu.com/linuxmirror/libgpiod/doc/html/group______high__level____.html#ga3ac28eb59bbd31b8b2298f76047d377d
+    
+    int pressed_pin = -1;
+
+    struct timespec ts = {
+        .tv_sec = 3600,
+        .tv_nsec = 0,
+    };
+
+    return gpiod_ctxless_event_monitor_multiple(GPIO_CHIP,
+                                        GPIOD_CTXLESS_EVENT_FALLING_EDGE,
+                                        pins,
+                                        5,
+                                        true,
+                                        "house-leds",
+                                        &ts,     // big timout
+                                        NULL,
+                                        button_presssed,
+                                        &pressed_pin
+                                        );
+}