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feat(lab03): setup epoll on 3 button

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This commit is contained in:
fastium
2026-04-24 14:08:39 +02:00
parent fbb9b5e993
commit c94273f8bf
2 changed files with 50 additions and 58 deletions
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104
src/03-led-controller/main.c
View File

@@ -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>
@@ -42,30 +18,36 @@
* power led - gpiol.10 --> gpio362
*/
#define GPIO_LED "/sys/class/gpio/gpio10"
#define LED "10"
#define GPIO_LED "/sys/class/gpio/gpio10"
#define LED "10"
#define GPIO_BTN1 "/sys/class/gpio/gpio0"
#define BTN1 "0"
#define BTN1 "0"
#define GPIO_BTN2 "/sys/class/gpio/gpio2"
#define BTN2 "2"
#define BTN2 "2"
#define GPIO_BTN3 "/sys/class/gpio/gpio3"
#define BTN3 "3"
#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);
if (btn1 < 0) {
perror("Failed to open button");
return 1;
// Open all button with the right flags
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) {
perror("Failed to add btn1 to epoll");
return 1;
for(int i=0; i<NBR_BTN; i++) {
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) {
// Read the new value. pread uses offset 0 so we don't need lseek()
pread(btn1, buf, sizeof(buf), 0);
for (int j = 0; j < NBR_BTN; j++) {
if (events[i].data.fd == btn[j]) {
// 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");
} else {
printf("Button 1 State: LOW (0)\n");
// Read the new value. pread uses offset 0 so we don't need lseek()
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 %d State: HIGH (1)\n", j+1);
} else {
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;
}

4
src/03-led-controller/setup.c
View File

@@ -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);