ESP32 TimerInterrupt Library
Posted: Sat Feb 22, 2020 9:16 pm
https://github.com/khoih-prog/ESP32TimerInterrupt
You can install directly from Arduino Library Manager
https://www.ardu-badge.com/ESP32TimerInterrupt
This library enables you to use Interrupt from Hardware Timers on an ESP32-based board. It now supports 16 ISR-based timers, while consuming only 1 hardware Timer. Timers' interval is very long (ulong millisecs). The most important feature is they're ISR-based timers. Therefore, their executions are not blocked by bad-behaving functions or tasks. This important feature is absolutely necessary for mission-critical tasks.
Why do we need this Hardware Timer Interrupt?
Imagine you have a system with a mission-critical function, measuring water level and control the sump pump or doing something much more important. You normally use a `software timer` to poll, or even place the function in loop(). But what if another function is blocking the loop() or setup().
So your function might not be executed, and the result would be disastrous.
You'd prefer to have your function called, no matter what happening with other functions (busy loop, bug, etc.).
The correct choice is to use a `Hardware Timer with Interrupt` to call your function.
These hardware timers, using interrupt, still work even if other functions are blocking. Moreover, they are much more precise (certainly depending on clock frequency accuracy) than other software timers using millis() or micros(). That's necessary if you need to measure some data requiring better accuracy.
Functions using normal software timers, relying on loop() and calling millis(), won't work if the loop() or setup() is blocked by certain operation. For example, certain function is blocking while it's connecting to WiFi or some services.
The catch is your function is now part of an ISR (Interrupt Service Routine), and must be lean / mean, and follow certain rules. More to read on:
Attach Interrupt(https://www.arduino.cc/reference/en/la ... interrupt/)
Important Notes:
1. Inside the ISR function, delay() won’t work and the value returned by millis() will not increment. Serial data received while in the function may be lost. You should declare as volatile any variables that you modify within the attached function.
2. Typically global variables are used to pass data between an ISR and the main program. To make sure variables shared between an ISR and the main program are updated correctly, declare them as volatile.
Sample Code
Before using any Hardware Timer, you have to make sure the Timer has not been used by any other purpose.
Timer0, Timer1, Timer2 and Timer3 are supported for ESP32.
You can install directly from Arduino Library Manager
https://www.ardu-badge.com/ESP32TimerInterrupt
This library enables you to use Interrupt from Hardware Timers on an ESP32-based board. It now supports 16 ISR-based timers, while consuming only 1 hardware Timer. Timers' interval is very long (ulong millisecs). The most important feature is they're ISR-based timers. Therefore, their executions are not blocked by bad-behaving functions or tasks. This important feature is absolutely necessary for mission-critical tasks.
Why do we need this Hardware Timer Interrupt?
Imagine you have a system with a mission-critical function, measuring water level and control the sump pump or doing something much more important. You normally use a `software timer` to poll, or even place the function in loop(). But what if another function is blocking the loop() or setup().
So your function might not be executed, and the result would be disastrous.
You'd prefer to have your function called, no matter what happening with other functions (busy loop, bug, etc.).
The correct choice is to use a `Hardware Timer with Interrupt` to call your function.
These hardware timers, using interrupt, still work even if other functions are blocking. Moreover, they are much more precise (certainly depending on clock frequency accuracy) than other software timers using millis() or micros(). That's necessary if you need to measure some data requiring better accuracy.
Functions using normal software timers, relying on loop() and calling millis(), won't work if the loop() or setup() is blocked by certain operation. For example, certain function is blocking while it's connecting to WiFi or some services.
The catch is your function is now part of an ISR (Interrupt Service Routine), and must be lean / mean, and follow certain rules. More to read on:
Attach Interrupt(https://www.arduino.cc/reference/en/la ... interrupt/)
Important Notes:
1. Inside the ISR function, delay() won’t work and the value returned by millis() will not increment. Serial data received while in the function may be lost. You should declare as volatile any variables that you modify within the attached function.
2. Typically global variables are used to pass data between an ISR and the main program. To make sure variables shared between an ISR and the main program are updated correctly, declare them as volatile.
Sample Code
Before using any Hardware Timer, you have to make sure the Timer has not been used by any other purpose.
Timer0, Timer1, Timer2 and Timer3 are supported for ESP32.
Code: Select all
//These define's must be placed at the beginning before #include "TimerInterrupt.h"
#define TIMER_INTERRUPT_DEBUG 1
#include "ESP32TimerInterrupt.h"
#ifndef LED_BUILTIN
#define LED_BUILTIN 2 // Pin D2 mapped to pin GPIO2/ADC12 of ESP32, control on-board LED
#endif
#define PIN_D23 23 // Pin D23 mapped to pin GPIO23/VSPI_MOSI of ESP32
void IRAM_ATTR TimerHandler0(void)
{
static bool toggle0 = false;
static bool started = false;
if (!started)
{
started = true;
pinMode(LED_BUILTIN, OUTPUT);
}
#if (TIMER_INTERRUPT_DEBUG > 0)
Serial.println("ITimer0: millis() = " + String(millis()));
#endif
//timer interrupt toggles pin LED_BUILTIN
digitalWrite(LED_BUILTIN, toggle0);
toggle0 = !toggle0;
}
void IRAM_ATTR TimerHandler1(void)
{
static bool toggle1 = false;
static bool started = false;
if (!started)
{
started = true;
pinMode(PIN_D23, OUTPUT);
}
#if (TIMER_INTERRUPT_DEBUG > 0)
Serial.println("ITimer1: millis() = " + String(millis()));
#endif
//timer interrupt toggles outputPin
digitalWrite(PIN_D23, toggle1);
toggle1 = !toggle1;
}
#define TIMER0_INTERVAL_MS 1000
#define TIMER1_INTERVAL_MS 5000
// Instantiate ESP32 timer0 and 1
ESP32Timer ITimer0(0);
ESP32Timer ITimer1(1);
void setup()
{
Serial.begin(115200);
Serial.println("\nStarting");
// Using ESP32 => 80 / 160 / 240MHz CPU clock ,
// For 64-bit timer counter
// For 16-bit timer prescaler up to 1024
// Interval in microsecs
if (ITimer0.attachInterruptInterval(TIMER0_INTERVAL_MS * 1000, TimerHandler0))
Serial.println("Starting ITimer0 OK, millis() = " + String(millis()));
else
Serial.println("Can't set ITimer0. Select another freq. or timer");
// Interval in microsecs
if (ITimer1.attachInterruptInterval(TIMER1_INTERVAL_MS * 1000, TimerHandler1))
Serial.println("Starting ITimer1 OK, millis() = " + String(millis()));
else
Serial.println("Can't set ITimer1. Select another freq. or timer");
}
void loop()
{
}