Is there a way to calculate -time interval- using Esp32 timers? - timer

Question

I want to calculate time interval with timers. I'm using arduino ide. Also i can not decide which library to useful.
I just tried something following code.
I'm using this library
#include <ESP32Time.h>
int a;
int b;
int ldrValue;
#define LDR 0
/* create a hardware timer */
hw_timer_t * timer = NULL;
int timeThatPast;
/* motor pin */
int motor = 14;
/* motor state */
volatile byte state = LOW;
void IRAM_ATTR onTimer(){
state = !state;
digitalWrite(motor, state);
}
void setup() {
Serial.begin(115200);
pinMode(motor, OUTPUT);
/* Use 1st timer of 4 */
/* 1 tick take 1/(80MHZ/80) = 1us so we set divider 80 and count up */
timer = timerBegin(0, 80, false);
/* Attach onTimer function to our timer */
timerAttachInterrupt(timer, &onTimer, true);
//********************ALARM*******************
/* Set alarm to call onTimer function every second 1 tick is 1us
=> 1 second is 1000000us */
/* Repeat the alarm (third parameter) */
timerAlarmWrite(timer, 7000000, false);
//********************************************
/* Start an alarm */
timerAlarmEnable(timer);
Serial.println("start timer");
}
void loop() {
int ldrValue = analogRead(LDR);
ldrValue = map(ldrValue, 0, 4095, 0, 10000);
if(ldrValue > 8500){
a = timerRead(timer);
digitalWrite(motor,HIGH);
while(1){
int ldrValue = analogRead(LDR);
ldrValue = map(ldrValue, 0, 4095, 0, 10000);
if(ldrValue < 8500){
b = timerRead(timer);
digitalWrite(motor,LOW);
Serial.print("Entering Loop");
Serial.println(a);
Serial.println("**********");
Serial.println("**********");
Serial.print("Exiting loop");
Serial.println(b);
int difference = b - a;
Serial.println("Difference");
Serial.println(difference);
break;
}
}
}
}

Answer 1

Use millis or micros if you need more precise timing.
Here is an example sketch:
long lastDoTime = 0;
void setup(){
Serial.begin(115200);
delay(1000);
Serial.println("Hello! We will do something at every ms");
}
void doThisAtEvery(int ms){
if( millis() - lastDoTime >= ms ){
// Must save the lastDoTime
lastDoTime = millis();
// Do some stuff at every ms
}
}
void loop(){
// It will do the thing in every 100 ms.
doThisAtEvery(100);
}
If you want to toggle a pin let's say every 100 microsec
long lastToggleTime = 0;
int motorPin = 14;
boolean lastPinState = LOW;
void setup(){
Serial.begin(115200);
}
void togglePinEvery(int micros){
if( micros() - lastToggleTime >= micros ){
lastToggleTime = micros();
digitalWrite(motorPin,!lastPinState);
lastPinState = !lastPinState;
}
}
void loop(){
togglePinEvery(100);
}
EDIT Since you wanted timers only.
Here is a detailed explanation about timers: https://techtutorialsx.com/2017/10/07/esp32-arduino-timer-interrupts/
Code example:
volatile int interruptCounter;
int totalInterruptCounter;
hw_timer_t * timer = NULL;
portMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED;
void IRAM_ATTR onTimer() {
portENTER_CRITICAL_ISR(&timerMux);
interruptCounter++;
portEXIT_CRITICAL_ISR(&timerMux);
}
void setup() {
Serial.begin(115200);
timer = timerBegin(0, 80, true);
timerAttachInterrupt(timer, &onTimer, true);
timerAlarmWrite(timer, 1000000, true);
timerAlarmEnable(timer);
}
void loop() {
if (interruptCounter > 0) {
portENTER_CRITICAL(&timerMux);
interruptCounter--;
portEXIT_CRITICAL(&timerMux);
totalInterruptCounter++;
Serial.print("An interrupt as occurred. Total number: ");
Serial.println(totalInterruptCounter);
}
}