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This library enables you to use Interrupt from Hardware Timers on an ESP32-C3-based board. These ESP32-C3 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 mandatory…

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ESP32_C3_TimerInterrupt Library

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Table of Contents

Important Change from v1.5.0

Please have a look at HOWTO Fix Multiple Definitions Linker Error

Why do we need this ESP32_C3_TimerInterrupt library

Features

This library enables you to use Interrupt from Hardware Timers on an ESP32_C3-based board.

The ESP32_C3 timer Interrupt control is different from that of ESP32, at least with the ESP32_C3 core v2.0.0-rc1. While the examples of current ESP32TimerInterrupt library can be compiled OK, they can't run yet. That's why this new ESP32_C3_TimerInterrupt library has been created.

As Hardware Timers are rare, and very precious assets of any board, this library now enables you to use up to 16 ISR-based Timers, while consuming only 1 Hardware Timer. Timers' interval is very long (ulong millisecs).

Now with these new 16 ISR-based timers, the maximum interval is practically unlimited (limited only by unsigned long milliseconds) while the accuracy is nearly perfect compared to software timers.

The most important feature is they're ISR-based timers. Therefore, their executions are not blocked by bad-behaving functions / tasks. This important feature is absolutely necessary for mission-critical tasks.

The ISR_Timer_Complex example will demonstrate the nearly perfect accuracy compared to software timers by printing the actual elapsed millisecs of each type of timers.

Being ISR-based timers, their executions are not blocked by bad-behaving functions / tasks, such as connecting to WiFi, Internet and Blynk services. You can also have many (up to 16) timers to use.

This non-being-blocked important feature is absolutely necessary for mission-critical tasks.

You'll see blynkTimer Software is blocked while system is connecting to WiFi / Internet / Blynk, as well as by blocking task in loop(), using delay() function as an example. The elapsed time then is very unaccurate

Why using ISR-based Hardware Timer Interrupt is better

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:

HOWTO Attach Interrupt

Currently supported Boards

  1. ESP32_C3-based boards, such as ESP32C3_DEV, LOLIN_C3_MINI, DFROBOT_BEETLE_ESP32_C3, ADAFRUIT_QTPY_ESP32C3, AirM2M_CORE_ESP32C3, XIAO_ESP32C3, etc.

Important Notes about ISR

  1. Inside the attached 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.

Prerequisites

  1. Arduino IDE 1.8.19+ for Arduino. GitHub release
  2. ESP32 Core 2.0.5+ for ESP32-S2-based boards. Latest release
  3. To use with certain example

Installation

Use Arduino Library Manager

The best and easiest way is to use Arduino Library Manager. Search for ESP32_C3_TimerInterrupt, then select / install the latest version. You can also use this link arduino-library-badge for more detailed instructions.

Manual Install

Another way to install is to:

  1. Navigate to ESP32_C3_TimerInterrupt page.
  2. Download the latest release ESP32_C3_TimerInterrupt-main.zip.
  3. Extract the zip file to ESP32_C3_TimerInterrupt-main directory
  4. Copy whole ESP32_C3_TimerInterrupt-main folder to Arduino libraries' directory such as ~/Arduino/libraries/.

VS Code & PlatformIO

  1. Install VS Code
  2. Install PlatformIO
  3. Install ESP32_C3_TimerInterrupt library by using Library Manager. Search for ESP32_C3_TimerInterrupt in Platform.io Author's Libraries
  4. Use included platformio.ini file from examples to ensure that all dependent libraries will installed automatically. Please visit documentation for the other options and examples at Project Configuration File

Note for Platform IO using ESP32 LittleFS

Necessary only for esp32 core v1.0.6-

From esp32 core v1.0.6+, LittleFS_esp32 v1.0.6 has been included and this step is not necessary anymore.

In Platform IO, to fix the error when using LittleFS_esp32 v1.0 for ESP32-based boards with ESP32 core v1.0.4- (ESP-IDF v3.2-), uncomment the following line

from

//#define CONFIG_LITTLEFS_FOR_IDF_3_2   /* For old IDF - like in release 1.0.4 */

to

#define CONFIG_LITTLEFS_FOR_IDF_3_2   /* For old IDF - like in release 1.0.4 */

It's advisable to use the latest LittleFS_esp32 v1.0.5+ to avoid the issue.

Thanks to Roshan to report the issue in Error esp_littlefs.c 'utime_p'

HOWTO Fix Multiple Definitions Linker Error

The current library implementation, using xyz-Impl.h instead of standard xyz.cpp, possibly creates certain Multiple Definitions Linker error in certain use cases.

You can include these .hpp or .h files

// Can be included as many times as necessary, without `Multiple Definitions` Linker Error
#include "ESP32_C3_TimerInterrupt.h"     //https://github.com/khoih-prog/ESP32_C3_TimerInterrupt

// Can be included as many times as necessary, without `Multiple Definitions` Linker Error
#include "ESP32_C3_ISR_Timer.hpp"         //https://github.com/khoih-prog/ESP32_C3_TimerInterrupt

in many files. But be sure to use the following .h file in just 1 .h, .cpp or .ino file, which must not be included in any other file, to avoid Multiple Definitions Linker Error

// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error
#include "ESP32_C3_ISR_Timer.h"           //https://github.com/khoih-prog/ESP32_C3_TimerInterrupt

Check the new multiFileProject example for a HOWTO demo.

HOWTO Use analogRead() with ESP32 running WiFi and/or BlueTooth (BT/BLE)

Please have a look at ESP_WiFiManager Issue 39: Not able to read analog port when using the autoconnect example to have more detailed description and solution of the issue.

1. ESP32 has 2 ADCs, named ADC1 and ADC2

2. ESP32 ADCs functions

  • ADC1 controls ADC function for pins GPIO32-GPIO39
  • ADC2 controls ADC function for pins GPIO0, 2, 4, 12-15, 25-27

3.. ESP32 WiFi uses ADC2 for WiFi functions

Look in file adc_common.c

In ADC2, there're two locks used for different cases:

  1. lock shared with app and Wi-Fi: ESP32: When Wi-Fi using the ADC2, we assume it will never stop, so app checks the lock and returns immediately if failed. ESP32S2: The controller's control over the ADC is determined by the arbiter. There is no need to control by lock.

  2. lock shared between tasks: when several tasks sharing the ADC2, we want to guarantee all the requests will be handled. Since conversions are short (about 31us), app returns the lock very soon, we use a spinlock to stand there waiting to do conversions one by one.

adc2_spinlock should be acquired first, then adc2_wifi_lock or rtc_spinlock.

  • In order to use ADC2 for other functions, we have to acquire complicated firmware locks and very difficult to do
  • So, it's not advisable to use ADC2 with WiFi/BlueTooth (BT/BLE).
  • Use ADC1, and pins GPIO32-GPIO39
  • If somehow it's a must to use those pins serviced by ADC2 (GPIO0, 2, 4, 12, 13, 14, 15, 25, 26 and 27), use the fix mentioned at the end of ESP_WiFiManager Issue 39: Not able to read analog port when using the autoconnect example to work with ESP32 WiFi/BlueTooth (BT/BLE).

More useful Information

The ESP32_C3 has two timer groups, each one with only one general purpose hardware timer. All the timers are based on 64 bits counters and 16 bit prescalers.

The timer counters can be configured to count up or down and support automatic reload and software reload.

They can also generate alarms when they reach a specific value, defined by the software. The value of the counter can be read by the software program.

Now with these new 16 ISR-based timers (while consuming only 1 hardware timer), the maximum interval is practically unlimited (limited only by unsigned long milliseconds). The accuracy is nearly perfect compared to software timers. The most important feature is they're ISR-based timers Therefore, their executions are not blocked by bad-behaving functions / tasks. This important feature is absolutely necessary for mission-critical tasks.

The ISR_Timer_Complex example will demonstrate the nearly perfect accuracy compared to software timers by printing the actual elapsed millisecs of each type of timers. Being ISR-based timers, their executions are not blocked by bad-behaving functions / tasks, such as connecting to WiFi, Internet and Blynk services. You can also have many (up to 16) timers to use. This non-being-blocked important feature is absolutely necessary for mission-critical tasks. You'll see blynkTimer Software is blocked while system is connecting to WiFi / Internet / Blynk, as well as by blocking task in loop(), using delay() function as an example. The elapsed time then is very unaccurate

How to use

Before using any Timer, you have to make sure the Timer has not been used by any other purpose.

Timer0, Timer1 are supported for ESP32_C3.

Using as follows:

// Can be included as many times as necessary, without `Multiple Definitions` Linker Error
#include "ESP32_C3_TimerInterrupt.h"

// Init ESP32_C3 timer 0 and 1
ESP32Timer ITimer0(0);
ESP32Timer ITimer1(1);

void setup()
{
  Serial.begin(115200);
  while (!Serial);
  
  delay(100);
  ...

  // 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.print(F("Starting  ITimer0 OK, millis() = ")); Serial.println(millis());
  }
  else
    Serial.println(F("Can't set ITimer0. Select another freq. or timer"));

  // Interval in microsecs
  if (ITimer1.attachInterruptInterval(TIMER1_INTERVAL_MS * 1000, TimerHandler1))
  {
    Serial.print(F("Starting  ITimer1 OK, millis() = ")); Serial.println(millis());
  }
  else
    Serial.println(F("Can't set ITimer1. Select another freq. or timer"));
}

Examples:

  1. Argument_None
  2. RPM_Measure
  3. SwitchDebounce
  4. TimerInterruptTest
  5. Change_Interval.
  6. ISR_16_Timers_Array
  7. ISR_16_Timers_Array_Complex
  8. multiFileProject. New

Example TimerInterruptTest

ESP32_C3_TimerInterrupt/examples/TimerInterruptTest/TimerInterruptTest.ino

Lines 40 to 179 in c593e91

// These define's must be placed at the beginning before #include "TimerInterrupt_Generic.h"
// _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4
// Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
#define TIMER_INTERRUPT_DEBUG 0
#define _TIMERINTERRUPT_LOGLEVEL_ 4
// Can be included as many times as necessary, without `Multiple Definitions` Linker Error
#include "ESP32_C3_TimerInterrupt.h"
// Don't use PIN_D1 in core v2.0.0 and v2.0.1. Check https://github.com/espressif/arduino-esp32/issues/5868
// Don't use PIN_D2 with ESP32_C3 (crash)
#define PIN_D19 19 // Pin D19 mapped to pin GPIO9 of ESP32
#define PIN_D3 3 // Pin D3 mapped to pin GPIO3/RX0 of ESP32
// With core v2.0.0+, you can't use Serial.print/println in ISR or crash.
// and you can't use float calculation inside ISR
// Only OK in core v1.0.6-
bool IRAM_ATTR TimerHandler0(void * timerNo)
{
static bool toggle0 = false;
//timer interrupt toggles pin PIN_D19
digitalWrite(PIN_D19, toggle0);
toggle0 = !toggle0;
return true;
}
bool IRAM_ATTR TimerHandler1(void * timerNo)
{
static bool toggle1 = false;
//timer interrupt toggles outputPin
digitalWrite(PIN_D3, toggle1);
toggle1 = !toggle1;
return true;
}
#define TIMER0_INTERVAL_MS 1000
#define TIMER0_DURATION_MS 5000
#define TIMER1_INTERVAL_MS 3000
#define TIMER1_DURATION_MS 15000
// Init ESP32 timer 0 and 1
ESP32Timer ITimer0(0);
ESP32Timer ITimer1(1);
void setup()
{
pinMode(PIN_D19, OUTPUT);
pinMode(PIN_D3, OUTPUT);
Serial.begin(115200);
while (!Serial && millis() < 5000);
delay(500);
Serial.print(F("\nStarting TimerInterruptTest on "));
Serial.println(ARDUINO_BOARD);
Serial.println(ESP32_C3_TIMER_INTERRUPT_VERSION);
Serial.print(F("CPU Frequency = "));
Serial.print(F_CPU / 1000000);
Serial.println(F(" MHz"));
// 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.print(F("Starting ITimer0 OK, millis() = "));
Serial.println(millis());
}
else
Serial.println(F("Can't set ITimer0. Select another freq. or timer"));
// Interval in microsecs
if (ITimer1.attachInterruptInterval(TIMER1_INTERVAL_MS * 1000, TimerHandler1))
{
Serial.print(F("Starting ITimer1 OK, millis() = "));
Serial.println(millis());
}
else
Serial.println(F("Can't set ITimer1. Select another freq. or timer"));
Serial.flush();
}
void loop()
{
static unsigned long lastTimer0 = 0;
static unsigned long lastTimer1 = 0;
static bool timer0Stopped = false;
static bool timer1Stopped = false;
if (millis() - lastTimer0 > TIMER0_DURATION_MS)
{
lastTimer0 = millis();
if (timer0Stopped)
{
Serial.print(F("Start ITimer0, millis() = "));
Serial.println(millis());
ITimer0.restartTimer();
}
else
{
Serial.print(F("Stop ITimer0, millis() = "));
Serial.println(millis());
ITimer0.stopTimer();
}
timer0Stopped = !timer0Stopped;
}
if (millis() - lastTimer1 > TIMER1_DURATION_MS)
{
lastTimer1 = millis();
if (timer1Stopped)
{
Serial.print(F("Start ITimer1, millis() = "));
Serial.println(millis());
ITimer1.restartTimer();
}
else
{
Serial.print(F("Stop ITimer1, millis() = "));
Serial.println(millis());
ITimer1.stopTimer();
}
timer1Stopped = !timer1Stopped;
}
}

Debug Terminal Output Samples

1. ISR_16_Timers_Array_Complex on ESP32C3_DEV

The following is the sample terminal output when running example ISR_16_Timers_Array_Complex on ESP32C3_DEV to demonstrate of ISR Hardware Timer, especially when system is very busy or blocked. The 16 independent ISR timers are programmed to be activated repetitively after certain intervals, is activated exactly after that programmed interval !!!

Starting ISR_16_Timers_Array_Complex on ESP32C3_DEV
ESP32_C3_TimerInterrupt v1.8.0
CPU Frequency = 160 MHz
[TISR] ESP32_C3_TimerInterrupt: _timerNo = 1, TIM_CLOCK_FREQ = 1000000.00
[TISR] TIMER_BASE_CLK = 80000000, TIMER_DIVIDER = 80
[TISR] _timerIndex = 0, _timerGroup = 1
[TISR] Timer freq = 100.00, _count = 0-10000
[TISR] timer_set_alarm_value = 10000.00
Starting ITimer OK, millis() = 2100
SimpleTimer : 2, ms : 12116, Dms : 10004
Timer : 0, programmed : 5000, actual : 5008
Timer : 1, programmed : 10000, actual : 0
Timer : 2, programmed : 15000, actual : 0
Timer : 3, programmed : 20000, actual : 0
Timer : 4, programmed : 25000, actual : 0
Timer : 5, programmed : 30000, actual : 0
Timer : 6, programmed : 35000, actual : 0
Timer : 7, programmed : 40000, actual : 0
Timer : 8, programmed : 45000, actual : 0
Timer : 9, programmed : 50000, actual : 0
Timer : 10, programmed : 55000, actual : 0
Timer : 11, programmed : 60000, actual : 0
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 22196, Dms : 10080
Timer : 0, programmed : 5000, actual : 5000
Timer : 1, programmed : 10000, actual : 10000
Timer : 2, programmed : 15000, actual : 15008
Timer : 3, programmed : 20000, actual : 20008
Timer : 4, programmed : 25000, actual : 0
Timer : 5, programmed : 30000, actual : 0
Timer : 6, programmed : 35000, actual : 0
Timer : 7, programmed : 40000, actual : 0
Timer : 8, programmed : 45000, actual : 0
Timer : 9, programmed : 50000, actual : 0
Timer : 10, programmed : 55000, actual : 0
Timer : 11, programmed : 60000, actual : 0
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 32276, Dms : 10080
Timer : 0, programmed : 5000, actual : 5000
Timer : 1, programmed : 10000, actual : 10000
Timer : 2, programmed : 15000, actual : 15000
Timer : 3, programmed : 20000, actual : 20008
Timer : 4, programmed : 25000, actual : 25008
Timer : 5, programmed : 30000, actual : 30008
Timer : 6, programmed : 35000, actual : 0
Timer : 7, programmed : 40000, actual : 0
Timer : 8, programmed : 45000, actual : 0
Timer : 9, programmed : 50000, actual : 0
Timer : 10, programmed : 55000, actual : 0
Timer : 11, programmed : 60000, actual : 0
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 42356, Dms : 10080
Timer : 0, programmed : 5000, actual : 5000
Timer : 1, programmed : 10000, actual : 10000
Timer : 2, programmed : 15000, actual : 15000
Timer : 3, programmed : 20000, actual : 20000
Timer : 4, programmed : 25000, actual : 25008
Timer : 5, programmed : 30000, actual : 30008
Timer : 6, programmed : 35000, actual : 35008
Timer : 7, programmed : 40000, actual : 40008
Timer : 8, programmed : 45000, actual : 0
Timer : 9, programmed : 50000, actual : 0
Timer : 10, programmed : 55000, actual : 0
Timer : 11, programmed : 60000, actual : 0
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 52436, Dms : 10080
Timer : 0, programmed : 5000, actual : 5000
Timer : 1, programmed : 10000, actual : 10000
Timer : 2, programmed : 15000, actual : 15000
Timer : 3, programmed : 20000, actual : 20000
Timer : 4, programmed : 25000, actual : 25000
Timer : 5, programmed : 30000, actual : 30008
Timer : 6, programmed : 35000, actual : 35008
Timer : 7, programmed : 40000, actual : 40008
Timer : 8, programmed : 45000, actual : 45008
Timer : 9, programmed : 50000, actual : 50008
Timer : 10, programmed : 55000, actual : 0
Timer : 11, programmed : 60000, actual : 0
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 62516, Dms : 10080
Timer : 0, programmed : 5000, actual : 5000
Timer : 1, programmed : 10000, actual : 10000
Timer : 2, programmed : 15000, actual : 15000
Timer : 3, programmed : 20000, actual : 20000
Timer : 4, programmed : 25000, actual : 25000
Timer : 5, programmed : 30000, actual : 30000
Timer : 6, programmed : 35000, actual : 35008
Timer : 7, programmed : 40000, actual : 40008
Timer : 8, programmed : 45000, actual : 45008
Timer : 9, programmed : 50000, actual : 50008
Timer : 10, programmed : 55000, actual : 55008
Timer : 11, programmed : 60000, actual : 60008
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 72596, Dms : 10080
Timer : 0, programmed : 5000, actual : 5000
Timer : 1, programmed : 10000, actual : 10000
Timer : 2, programmed : 15000, actual : 15000
Timer : 3, programmed : 20000, actual : 20000
Timer : 4, programmed : 25000, actual : 25000
Timer : 5, programmed : 30000, actual : 30000
Timer : 6, programmed : 35000, actual : 35000
Timer : 7, programmed : 40000, actual : 40008
Timer : 8, programmed : 45000, actual : 45008
Timer : 9, programmed : 50000, actual : 50008
Timer : 10, programmed : 55000, actual : 55008
Timer : 11, programmed : 60000, actual : 60008
Timer : 12, programmed : 65000, actual : 65008
Timer : 13, programmed : 70000, actual : 70008
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 82676, Dms : 10080
Timer : 0, programmed : 5000, actual : 5000
Timer : 1, programmed : 10000, actual : 10000
Timer : 2, programmed : 15000, actual : 15000
Timer : 3, programmed : 20000, actual : 20000
Timer : 4, programmed : 25000, actual : 25000
Timer : 5, programmed : 30000, actual : 30000
Timer : 6, programmed : 35000, actual : 35000
Timer : 7, programmed : 40000, actual : 40000
Timer : 8, programmed : 45000, actual : 45008
Timer : 9, programmed : 50000, actual : 50008
Timer : 10, programmed : 55000, actual : 55008
Timer : 11, programmed : 60000, actual : 60008
Timer : 12, programmed : 65000, actual : 65008
Timer : 13, programmed : 70000, actual : 70008
Timer : 14, programmed : 75000, actual : 75008
Timer : 15, programmed : 80000, actual : 80008

2. TimerInterruptTest on ESP32C3_DEV

The following is the sample terminal output when running example TimerInterruptTest to demonstrate how to start/stop Hardware Timers.

Starting TimerInterruptTest on ESP32C3_DEV
ESP32_C3_TimerInterrupt v1.8.0
CPU Frequency = 160 MHz
[TISR] ESP32_C3_TimerInterrupt: _timerNo = 0, TIM_CLOCK_FREQ = 1000000.00
[TISR] TIMER_BASE_CLK = 80000000, TIMER_DIVIDER = 80
[TISR] _timerIndex = 0, _timerGroup = 0
[TISR] Timer freq = 1.00, _count = 0-1000000
[TISR] timer_set_alarm_value = 1000000.00
Starting  ITimer0 OK, millis() = 212
[TISR] ESP32_C3_TimerInterrupt: _timerNo = 1, TIM_CLOCK_FREQ = 1000000.00
[TISR] TIMER_BASE_CLK = 80000000, TIMER_DIVIDER = 80
[TISR] _timerIndex = 0, _timerGroup = 1
[TISR] Timer freq = 0.33, _count = 0-3000000
[TISR] timer_set_alarm_value = 3000000.00
Starting  ITimer1 OK, millis() = 237
Stop ITimer0, millis() = 5001
Start ITimer0, millis() = 10002
Stop ITimer1, millis() = 15001
Stop ITimer0, millis() = 15003
Start ITimer0, millis() = 20004
Stop ITimer0, millis() = 25005
Start ITimer1, millis() = 30002
Start ITimer0, millis() = 30006

3. Change_Interval on ESP32C3_DEV

The following is the sample terminal output when running example Change_Interval to demonstrate how to change Timer Interval on-the-fly

Starting Change_Interval on ESP32C3_DEV
ESP32_C3_TimerInterrupt v1.8.0
CPU Frequency = 160 MHz
[TISR] ESP32_C3_TimerInterrupt: _timerNo = 0, TIM_CLOCK_FREQ = 1000000.00
[TISR] TIMER_BASE_CLK = 80000000, TIMER_DIVIDER = 80
[TISR] _timerIndex = 0, _timerGroup = 0
[TISR] Timer freq = 0.50, _count = 0-2000000
[TISR] timer_set_alarm_value = 2000000.00
Starting  ITimer0 OK, millis() = 212
[TISR] ESP32_C3_TimerInterrupt: _timerNo = 1, TIM_CLOCK_FREQ = 1000000.00
[TISR] TIMER_BASE_CLK = 80000000, TIMER_DIVIDER = 80
[TISR] _timerIndex = 0, _timerGroup = 1
[TISR] Timer freq = 0.20, _count = 0-5000000
[TISR] timer_set_alarm_value = 5000000.00
Starting  ITimer1 OK, millis() = 237
Time = 10001, Timer0Count = 5, Timer1Count = 2
Time = 20002, Timer0Count = 10, Timer1Count = 4
[TISR] ESP32_C3_TimerInterrupt: _timerNo = 0, TIM_CLOCK_FREQ = 1000000.00
[TISR] TIMER_BASE_CLK = 80000000, TIMER_DIVIDER = 80
[TISR] _timerIndex = 0, _timerGroup = 0
[TISR] Timer freq = 0.25, _count = 0-4000000
[TISR] timer_set_alarm_value = 4000000.00
[TISR] ESP32_C3_TimerInterrupt: _timerNo = 1, TIM_CLOCK_FREQ = 1000000.00
[TISR] TIMER_BASE_CLK = 80000000, TIMER_DIVIDER = 80
[TISR] _timerIndex = 0, _timerGroup = 1
[TISR] Timer freq = 0.10, _count = 0-10000000
[TISR] timer_set_alarm_value = 10000000.00
Changing Interval, Timer0 = 4000,  Timer1 = 10000
Time = 30003, Timer0Count = 12, Timer1Count = 4

4. Argument_None on ESP32C3_DEV

The following is the sample terminal output when running example Argument_None

Starting Argument_None on ESP32C3_DEV
ESP32_C3_TimerInterrupt v1.8.0
CPU Frequency = 160 MHz
[TISR] ESP32_C3_TimerInterrupt: _timerNo = 0, TIM_CLOCK_FREQ = 1000000.00
[TISR] TIMER_BASE_CLK = 80000000, TIMER_DIVIDER = 80
[TISR] _timerIndex = 0, _timerGroup = 0
[TISR] Timer freq = 1.00, _count = 0-1000000
[TISR] timer_set_alarm_value = 1000000.00
Starting  ITimer0 OK, millis() = 212
[TISR] ESP32_C3_TimerInterrupt: _timerNo = 1, TIM_CLOCK_FREQ = 1000000.00
[TISR] TIMER_BASE_CLK = 80000000, TIMER_DIVIDER = 80
[TISR] _timerIndex = 0, _timerGroup = 1
[TISR] Timer freq = 0.20, _count = 0-5000000
[TISR] timer_set_alarm_value = 5000000.00
Starting  ITimer1 OK, millis() = 237

Debug

Debug is enabled by default on Serial.

You can also change the debugging level (TIMERINTERRUPT_LOGLEVEL) from 0 to 4

// These define's must be placed at the beginning before #include "ESP32_C3_TimerInterrupt.h"
// _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4
// Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
#define TIMER_INTERRUPT_DEBUG         0
#define _TIMERINTERRUPT_LOGLEVEL_     0

Troubleshooting

If you get compilation errors, more often than not, you may need to install a newer version of the core for Arduino boards.

Sometimes, the library will only work if you update the board core to the latest version because I am using newly added functions.

Issues

Submit issues to: ESP32_C3_TimerInterrupt issues

TO DO

  1. Search for bug and improvement.

DONE

  1. Basic hardware timers for ESP32_C3.
  2. More hardware-initiated software-enabled timers
  3. Longer time interval
  4. Similar features for remaining Arduino boards such as SAMD21, SAMD51, SAM-DUE, nRF52, ESP8266, STM32, etc.
  5. Fix compiler errors due to conflict to some libraries.
  6. Add complex examples.
  7. Fix multiple-definitions linker error. Drop src_cpp and src_h directories
  8. Avoid deprecated functions.
  9. Optimize library code by using reference-passing instead of value-passing
  10. Suppress errors and warnings for new ESP32 core v2.0.4+
  11. Add support to
  • ESP32_C3 : LOLIN_C3_MINI, DFROBOT_BEETLE_ESP32_C3, ADAFRUIT_QTPY_ESP32C3, AirM2M_CORE_ESP32C3, XIAO_ESP32C3
  1. Use allman astyle and add utils

Contributions and Thanks

Many thanks for everyone for bug reporting, new feature suggesting, testing and contributing to the development of this library.

Contributing

If you want to contribute to this project:

  • Report bugs and errors
  • Ask for enhancements
  • Create issues and pull requests
  • Tell other people about this library

License

  • The library is licensed under MIT

Copyright

Copyright (C) 2021- Khoi Hoang

About

This library enables you to use Interrupt from Hardware Timers on an ESP32-C3-based board. These ESP32-C3 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 mandatory…

Topics

measure timer esp32 accuracy espressif isr non-blocking timers interrupt precise mission-critical esp32-arduino esp32-library arduino-libraries hardware-timers timerinterrupt timerinterrupt-library esp32-c3 misssion-critical-tasks

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Releases 5

v1.8.0 to fix doubled time for ESP32_C3 and to use `allman astyle` Latest
Nov 16, 2022
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