From dc895bcc1d1ab0264cf81bd19acf8297b1b31094 Mon Sep 17 00:00:00 2001
From: Daniel Meiburg <key@dmeiburg.de>
Date: Fri, 3 May 2024 12:05:08 +0200
Subject: [PATCH] Working example of interation with led, button and ds18b20

---
 io.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)
 create mode 100644 io.c

diff --git a/io.c b/io.c
new file mode 100644
index 0000000..d7d6a07
--- /dev/null
+++ b/io.c
@@ -0,0 +1,129 @@
+// This document implements some function to interact with an 
+// Raspberry Pi 4 and some external components.
+// Used components: DS18B20, and LED and a push button.
+
+// libgpiod is used for the communication with the GPIOs
+#include <gpiod.h>
+#include <stdio.h>
+#include <unistd.h>  // For sleep()
+#include <fcntl.h>
+
+
+#define GPIO_CHIP    "gpiochip0"
+#define LED_GPIO_PIN     18
+#define BUTTON_GPIO_PIN  22
+#define LED_BLINK_TIME   1  // Blink delay in seconds
+#define SENSOR_PATH   "/sys/bus/w1/devices/28-000000306565/temperature"  // DS18B20 sensor address
+
+// function to set the LED state by passing the pin and state
+void set_led(int pin, int state) {
+    struct gpiod_chip *chip;
+    struct gpiod_line *line;
+
+    chip = gpiod_chip_open_by_name(GPIO_CHIP);
+    if (!chip) {
+        perror("Failed to open GPIO chip");
+        return;
+    }
+
+    line = gpiod_chip_get_line(chip, pin);
+    if (!line) {
+        perror("Failed to get GPIO line");
+        gpiod_chip_close(chip);
+        return;
+    }
+
+    if (gpiod_line_request_output(line, "gpio-led", 0) < 0) {
+        perror("Failed to request line as output");
+        gpiod_chip_close(chip);
+        return;
+    }
+
+    // Set the LED state
+    gpiod_line_set_value(line, state);
+
+    // Release the GPIO line and chip
+    gpiod_line_release(line);
+    gpiod_chip_close(chip);
+}
+
+// function to blink the LED by passing the pin, number of blinks and the delay
+void blink_led(int pin, int time, int delay) {
+    for (int i = 0; i < time; i++) {
+        set_led(pin, 1);
+        sleep(delay);
+        set_led(pin, 0);
+        sleep(delay);
+    }
+}
+
+float read_temperature() {
+	int fd;
+	float temperature;
+    char buf[16];  // Large enough to hold the temperature string
+
+    fd = open(SENSOR_PATH, O_RDONLY);
+    if (fd == -1) {
+        perror("Failed to open temperature file");
+        return -1;  // Return an error indicator
+    }
+
+    ssize_t numRead = read(fd, buf, sizeof(buf) - 1);
+    if (numRead == -1) {
+        perror("Failed to read temperature file");
+        close(fd);
+        return -1;  // Return an error indicator
+    }
+
+    buf[numRead] = '\0';  // Null-terminate the string
+    temperature = atof(buf) / 1000;  // Convert the string to an integer
+    close(fd);
+
+    return temperature;
+}
+
+// funciton to read button status
+int read_button(int pin) {
+    struct gpiod_chip *chip;
+    struct gpiod_line *line;
+    int value;
+
+    chip = gpiod_chip_open_by_name(GPIO_CHIP);
+    if (!chip) {
+        perror("Failed to open GPIO chip");
+        return -1;
+    }
+
+    line = gpiod_chip_get_line(chip, pin);
+    if (!line) {
+        perror("Failed to get GPIO line");
+        gpiod_chip_close(chip);
+        return -1;
+    }
+
+    if (gpiod_line_request_input(line, "gpio-button") < 0) {
+        perror("Failed to request line as input");
+        gpiod_chip_close(chip);
+        return -1;
+    }
+
+    value = gpiod_line_get_value(line);
+
+    // Release the GPIO line and chip
+    gpiod_line_release(line);
+    gpiod_chip_close(chip);
+
+    return value;
+}
+
+int main(void) {
+//    printf("Temperature: %.2f\n", read_temperature(SENSOR_ADDRESS));
+//    blink_led(LED_GPIO_PIN, 5, LED_BLINK_TIME);
+//	printf("Temperature: %.2f\n", read_temperature());
+    //	check button status and sleep for a second
+    while(1){
+        printf("Button status: %d\n", read_button(BUTTON_GPIO_PIN));
+        sleep(1);
+    }
+    return 0;
+}