ESP32 - Multi Tasking with while in a task - arduino

Question

I try to build a chrono laser with two ESP32 and two LDR.
I have two ESP32:
One do a ACCESS Point with a LDR
Second connect to the AP, have the algorithm of the laser chrono and a second LDR
In the second one, i try also to have a WebServer so i can connect with my phone and restart the chrono.
I try to do multitasking but everytime my ESP32 restart :
18:10:42.625 -> E (5775) task_wdt: Task watchdog got triggered. The following tasks did not reset the watchdog in time:
18:10:42.672 -> E (5775) task_wdt: - IDLE0 (CPU 0)
18:10:42.672 -> E (5775) task_wdt: Tasks currently running:
18:10:42.672 -> E (5775) task_wdt: CPU 0: Task1
18:10:42.672 -> E (5775) task_wdt: CPU 1: Task2
18:10:42.672 -> E (5775) task_wdt: Aborting.
18:10:42.672 -> abort() was called at PC 0x400d9033 on core 0
You can find my code here:
https://create.arduino.cc/editor/marcoberle/c4762636-36c6-4551-92f2-935021a001c9/preview
My code :
// Load Wi-Fi library
#include <WiFi.h>
#include <HTTPClient.h>
//Declaration of PIN
const int departReceiver = 4; // the number of the pin
const int LED_BUILTIN = 2;
// Replace with your network credentials
const char* ssid = "ESP32-ARRIVE";
const char* password = "123456789";
// Set web server port number to 80
WiFiServer server(80);
WiFiClient client = server.available();
//Your IP address or domain name with URL path
const char* serverNameArrive = "http://192.168.4.1/arrive";
// Variable to store the HTTP request
String header;
// Auxiliar variables to store the current output state
String output26State = "off";
String output27State = "off";
// Assign output variables to GPIO pins
const int output26 = 26;
const int output27 = 27;
// Current time
unsigned long currentTime = millis();
// Previous time
unsigned long previousTime = 0;
// Define timeout time in milliseconds (example: 2000ms = 2s)
const long timeoutTime = 2000;
TaskHandle_t Task1;
TaskHandle_t Task2;
void setup() {
Serial.begin(115200);
pinMode(departReceiver, INPUT);
// Initialize the output variables as outputs
pinMode(output26, OUTPUT);
pinMode(output27, OUTPUT);
// Set outputs to LOW
digitalWrite(output26, LOW);
digitalWrite(output27, LOW);
// Connect to Wi-Fi network with SSID and password
Serial.print("Connecting to ");
Serial.println(ssid);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
// Print local IP address and start web server
Serial.println("");
Serial.println("WiFi connected.");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
server.begin();
client = server.available();
//create a task that will be executed in the Task1code() function, with priority 1 and executed on core 0
xTaskCreatePinnedToCore(
Task1code, /* Task function. */
"Task1", /* name of task. */
10000, /* Stack size of task */
NULL, /* parameter of the task */
6, /* priority of the task */
&Task1, /* Task handle to keep track of created task */
0); /* pin task to core 0 */
delay(500);
//create a task that will be executed in the Task2code() function, with priority 1 and executed on core 1
xTaskCreatePinnedToCore(
Task2code, /* Task function. */
"Task2", /* name of task. */
10000, /* Stack size of task */
NULL, /* parameter of the task */
7, /* priority of the task */
&Task2, /* Task handle to keep track of created task */
1); /* pin task to core 1 */
delay(500);
}
//CHRONO VAR
unsigned int departStatus = 0;
unsigned int arriveStatus = 0;
unsigned int start_time = 0;
unsigned int stop_time = 0;
unsigned int total_time = 0;
const unsigned int OFF = 0;
const unsigned int ON = 1;
String httpGETRequest(const char* serverName) {
HTTPClient http;
// Your IP address with path or Domain name with URL path
http.begin(serverName);
// Send HTTP POST request
int httpResponseCode = http.GET();
String payload = "--";
if (httpResponseCode > 0) {
payload = http.getString();
}
else {
}
// Free resources
http.end();
return payload;
}
String ChronoLog = "";
int reset = 0;
void Chrono () {
if (reset == 0) {
reset = 1;
ChronoLog = "<p>ALGO START</p>";
Serial.println("ALGO START");
while (departStatus == OFF) {
departStatus = digitalRead(departReceiver);
}
ChronoLog += "<p>Borne de début prête</p>";
Serial.println("Borne de début prête");
while (arriveStatus == OFF) {
arriveStatus = httpGETRequest(serverNameArrive).toInt();
}
ChronoLog += "<p>Borne de fin prête</p>";
ChronoLog += "<p>En attente du courreur</p>";
Serial.println("Borne de fin prête");
Serial.println("En attente du courreur");
while (departStatus == ON) {
departStatus = digitalRead(departReceiver);
}
ChronoLog += "<p>Courreur en place</p>";
Serial.println("Courreur en place");
digitalWrite(LED_BUILTIN, HIGH);
while (departStatus == OFF) {
departStatus = digitalRead(departReceiver);
}
ChronoLog += "<p>Chrono lancé</p>";
Serial.println("Chrono lancé");
start_time = millis();
while (arriveStatus == ON) {
arriveStatus = httpGETRequest(serverNameArrive).toInt();
}
stop_time = millis();
total_time = stop_time - start_time;
ChronoLog += "<p>Courru en </p>";
float timeSe = total_time * 0.001;
//ChronoLog += "<p><b>" + String(timeSe) + "</b></p>" ;
Serial.println("Courru en");
Serial.println(timeSe);
}
}
void ResetChrono () {
reset = 0;
departStatus = 0;
arriveStatus = 0;
start_time = 0;
stop_time = 0;
total_time = 0;
}
void Webserver() {
// Listen for incoming clients
client = server.available();
if (client) { // If a new client connects,
currentTime = millis();
previousTime = currentTime;
Serial.println("New Client."); // print a message out in the serial port
String currentLine = ""; // make a String to hold incoming data from the client
while (client.connected() && currentTime - previousTime <= timeoutTime) { // loop while the client's connected
currentTime = millis();
if (client.available()) { // if there's bytes to read from the client,
char c = client.read(); // read a byte, then
Serial.write(c); // print it out the serial monitor
header += c;
if (c == '\n') { // if the byte is a newline character
// if the current line is blank, you got two newline characters in a row.
// that's the end of the client HTTP request, so send a response:
if (currentLine.length() == 0) {
// HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
// and a content-type so the client knows what's coming, then a blank line:
client.println("HTTP/1.1 200 OK");
client.println("Content-type:text/html");
client.println("Connection: close");
client.println();
//RESET CHRONO
if (header.indexOf("GET /RESET") >= 0) {
ResetChrono();
}
// turns the GPIOs on and off
if (header.indexOf("GET /26/on") >= 0) {
Serial.println("GPIO 26 on");
output26State = "on";
digitalWrite(output26, HIGH);
} else if (header.indexOf("GET /26/off") >= 0) {
Serial.println("GPIO 26 off");
output26State = "off";
digitalWrite(output26, LOW);
} else if (header.indexOf("GET /27/on") >= 0) {
Serial.println("GPIO 27 on");
output27State = "on";
digitalWrite(output27, HIGH);
} else if (header.indexOf("GET /27/off") >= 0) {
Serial.println("GPIO 27 off");
output27State = "off";
digitalWrite(output27, LOW);
}
// Display the HTML web page
client.println("<!DOCTYPE html><html>");
client.println("<head><meta name=\"viewport\" content=\"width=device-width, initial-scale=1\">");
//Chrono(client);
client.println("<link rel=\"icon\" href=\"data:,\">");
// CSS to style the on/off buttons
// Feel free to change the background-color and font-size attributes to fit your preferences
client.println("<style>html { font-family: Helvetica; display: inline-block; margin: 0px auto; text-align: center;}");
client.println(".button { background-color: #4CAF50; border: none; color: white; padding: 16px 40px;");
client.println("text-decoration: none; font-size: 30px; margin: 2px; cursor: pointer;}");
client.println(".button2 {background-color: #555555;}</style></head>");
// Web Page Heading
client.println("<body><h1>CHRONO</h1>");
client.println(ChronoLog);
client.println("<p><button class=\"button\">RESET</button></p>");
// Display current state, and ON/OFF buttons for GPIO 26
client.println("<p>GPIO 26 - State " + output26State + "</p>");
// If the output26State is off, it displays the ON button
if (output26State == "off") {
client.println("<p><button class=\"button\">ON</button></p>");
} else {
client.println("<p><button class=\"button button2\">OFF</button></p>");
}
// Display current state, and ON/OFF buttons for GPIO 27
client.println("<p>GPIO 27 - State " + output27State + "</p>");
// If the output27State is off, it displays the ON button
if (output27State == "off") {
client.println("<p><button class=\"button\">ON</button></p>");
} else {
client.println("<p><button class=\"button button2\">OFF</button></p>");
}
client.println("</body></html>");
// The HTTP response ends with another blank line
client.println();
// Break out of the while loop
break;
} else { // if you got a newline, then clear currentLine
currentLine = "";
}
} else if (c != '\r') { // if you got anything else but a carriage return character,
currentLine += c; // add it to the end of the currentLine
}
}
}
// Clear the header variable
header = "";
// Close the connection
client.stop();
Serial.println("Client disconnected.");
Serial.println("");
}
}
//Task1code: blinks an LED every 1000 ms
void Task1code( void * pvParameters ){
Serial.print("Task1 running on core ");
Serial.println(xPortGetCoreID());
for(;;){
Chrono();
}
}
//Task2code: blinks an LED every 700 ms
void Task2code( void * Parameters ){
Serial.print("Task2 running on core ");
Serial.println(xPortGetCoreID());
for(;;){
Webserver();
}
}
void loop() {
}
Do you have any suggestion to optimize my code or a solution to not have the problem anymore ?

Answer 1

You're getting watchdog timer resets. That means your code has been running for too long without resetting a timer that's used to recover from crashes and infinite loops. This timer is handled automatically by the underlying code in the Arduino Core.
Your Chrono and Webserver tasks simply won't work the way you've written them. They never yield the processor. The ESP32 does not do multitasking the way Linux or Windows does. Multitasking on the ESP32 is non-preemptive. A task runs until it says "okay, I've done enough, someone else can run now". These two tasks never do that, so the watchdog timer goes off. Even if the watchdog timer didn't go off, this wouldn't work because nothing else would get the chance to run.
At the least you need to yield the processor in each of the tasks:
for(;;){
Chrono();
}
should be:
for(;;){
Chrono();
delay(1);
}
and
for(;;){
Webserver();
}
should be
for(;;){
Webserver();
delay(1);
}
Your code also has a lot of places where you do things like this:
while (departStatus == OFF) {
departStatus = digitalRead(departReceiver);
}
If departStatus stays OFF for too long, this will trigger the watchdog timer.
Any time you have a loop like this you need to make sure that the underlying system has a change to run once in a while.
Rewrite every single while loop that you have that's like that to call delay(1); - that will give the Arduino Core a chance to reset the watchdog timer.
Like so:
while (departStatus == OFF) {
departStatus = digitalRead(departReceiver);
delay(1);
}

Answer 2

I try a method i found on the web, and it's works.
Add libraries :
#include "soc/timer_group_struct.h"
#include "soc/timer_group_reg.h"
Create a method:
void feedthedog () {
TIMERG0.wdt_wprotect = TIMG_WDT_WKEY_VALUE;
TIMERG0.wdt_feed = 1;
TIMERG0.wdt_wprotect = 0;
}
Add execution of the method in every while
while (departStatus == OFF) {
feedthedog();
departStatus = digitalRead(departReceiver);
}
I can wait, refresh page on the webserver, i don't get error :
19:38:40.321 -> Task1 running on core 0
19:38:40.321 -> ALGO START
19:39:20.937 -> Borne de début prête
19:39:39.093 -> Borne de fin prête
19:39:39.093 -> En attente du courreur
19:39:39.140 -> Courreur en place
19:39:51.840 -> Chrono lancé
19:39:58.804 -> Courru en
19:39:58.804 -> 6.99
19:39:58.804 -> Tâche fini
I put my update code here:
https://create.arduino.cc/editor/marcoberle/cb88dff8-d56c-422d-9f2e-4011ea2b80f4/preview