feat(lab03): setup epoll on 3 button

src/03-led-controller/main.c

@@ -1,27 +1,3 @@
-/**
- * Copyright 2018 University of Applied Sciences Western Switzerland / Fribourg
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- * Project: HEIA-FR / HES-SO MSE - MA-CSEL1 Laboratory
- *
- * Abstract: System programming -  file system
- *
- * Purpose: NanoPi silly status led control system
- *
- * Autĥor:  Daniel Gachet
- * Date:    07.11.2018
- */
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
@@ -52,20 +28,26 @@
 #define GPIO_BTN3      "/sys/class/gpio/gpio3"
 #define BTN3           "3"
 
+#define NBR_BTN 3
 
-
+// constant
+const char* GPIO_BTN[NBR_BTN] = {GPIO_BTN1, GPIO_BTN2, GPIO_BTN3};
+const char* BTN[NBR_BTN] =  {BTN1, BTN2, BTN3};
 
 int main(void)
 {
-    printf("Starting Button 1 Test...\n");
 
-    int btn1 = open_btn(GPIO_BTN1, BTN1);
+    // Open all button with the right flags
-    if (btn1 < 0) {
+    int btn[NBR_BTN] = {0};
+    for(int i=0; i<NBR_BTN; i++) {
+        btn[i] = open_btn(GPIO_BTN[i], BTN[i]);
+        if (btn[i] < 0) {
             perror("Failed to open button");
             return 1;
         }
+    }
 
-    // 1. Create epoll instance
+    // Create epoll instance to control all button files
     int epfd = epoll_create1(0);
     if (epfd < 0) {
         perror("Failed to create epoll");
@@ -73,25 +55,29 @@ int main(void)
     }
 
     // 2. Add button to epoll
-    struct epoll_event ev;
+    struct epoll_event ev[NBR_BTN];
     // CRITICAL: Sysfs GPIOs use EPOLLPRI (priority data) and EPOLLERR, not EPOLLIN!
-    ev.events = EPOLLPRI | EPOLLERR | EPOLLET;
-    ev.data.fd = btn1;
 
-    if (epoll_ctl(epfd, EPOLL_CTL_ADD, btn1, &ev) < 0) {
+    for(int i=0; i<NBR_BTN; i++) {
-        perror("Failed to add btn1 to epoll");
+        ev[i].events = EPOLLPRI | EPOLLERR | EPOLLET;
+        ev[i].data.fd = btn[i];
+        if (epoll_ctl(epfd, EPOLL_CTL_ADD, btn[i], &ev[i]) < 0) {
+            perror("Failed to add button to epoll");
             return 1;
         }
+    }
 
-    // 3. Dummy read to clear initial state before waiting
+    // Dummy read to clear initial state before waiting
     char buf[2];
-    pread(btn1, buf, sizeof(buf), 0);
+    for(int i=0; i<NBR_BTN; i++) {
+        pread(btn[i], buf, sizeof(buf), 0);
+    }
 
-    printf("Waiting for button presses (CPU should be at 0%%)...\n");
+    printf("Waiting for button presses...\n");
 
-    // 4. Event loop
+    // Event main loop
     while (1) {
-        struct epoll_event events[1]; // We only care about 1 event for now
+        struct epoll_event events[NBR_BTN]; // We only care about 1 event for now
 
         // Timeout is -1: Block infinitely until an event occurs!
         int n = epoll_wait(epfd, events, 1, -1);
@@ -102,21 +88,27 @@ int main(void)
         }
 
         for (int i = 0; i < n; i++) {
-            if (events[i].data.fd == btn1) {
+            for (int j = 0; j < NBR_BTN; j++) {
+                if (events[i].data.fd == btn[j]) {
+
                     // Read the new value. pread uses offset 0 so we don't need lseek()
-                pread(btn1, buf, sizeof(buf), 0);
+                    pread(btn[j], buf, sizeof(buf), 0);
 
                     // Print the result. '1' or '0' depends on your hardware pull-up/down resistors
                     if (buf[0] == '1') {
-                    printf("Button 1 State: HIGH (1)\n");
+                        printf("Button %d State: HIGH (1)\n", j+1);
                     } else {
-                    printf("Button 1 State: LOW (0)\n");
+                        printf("Button %d State: LOW (0)\n", j+1);
                     }
                 }
+
+            }
         }
     }
 
-    close(btn1);
+    for (int i=0; i<NBR_BTN; i++) {
+        close(btn[i]);
+    }
     close(epfd);
     return 0;
 }

src/03-led-controller/setup.c

@@ -11,7 +11,7 @@
 #define GPIO_EXPORT   "/sys/class/gpio/export"
 #define GPIO_UNEXPORT "/sys/class/gpio/unexport"
 
-static int open_led(char* gpio_path, char* pin) {
+static int open_led(const char* gpio_path, const char* pin) {
 
     // unexport pin out of sysfs (reinitialization)
     int f = open(GPIO_UNEXPORT, O_WRONLY);
@@ -41,7 +41,7 @@ static int open_led(char* gpio_path, char* pin) {
     return f;
 }
 
-static int open_btn(char* gpio_path, char* pin) {
+static int open_btn(const char* gpio_path, const char* pin) {
     int f = open(GPIO_UNEXPORT, O_WRONLY);
     write(f, pin, strlen(pin));
     close(f);