How To Install Using Arduino Library Manager
This library enables you to use Interrupt from Hardware Timers on ESP32_C3-based boards.
The ESP32_C3 timer Interrupt control is different from that of ESP32, at least with the ESP32 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 different ISR-based timers, while actually 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 ESP32_C3_TimerInterrupt Library
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 asoftware 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 on-time or not at all, 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), must be lean and mean, and follow certain rules. More to read on:
HOWTO Attach 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 ISR 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.
Initial Release v1.4.0
1. Initial coding to support ESP32_C3
2. Sync with ESP32_S2_TimerInterrupt Library v1.4.0
Currently Supported Boards
- ESP32_C3-based boards, such as ESP32C3_DEV, etc
Examples:
1. Argument_None
2. Change_Interval
3. ISR_RPM_Measure
4. RPM_Measure
5. SwitchDebounce
6. TimerInterruptTest
7. ISR_16_Timers_Array
8. ISR_16_Timers_Array_Complex
Example 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
Code: Select all
Starting Change_Interval on ESP32C3_DEV
ESP32_C3_TimerInterrupt v1.4.0
CPU Frequency = 160 MHz
ITimer0: millis() = 287
Starting ITimer0 OK, millis() = 289
ITimer1: millis() = 291
Starting ITimer1 OK, millis() = 294
ITimer0: millis() = 2287
ITimer0: millis() = 4287
ITimer1: millis() = 5289
ITimer0: millis() = 6287
ITimer0: millis() = 8287
Time = 10001, Timer0Count = 5, Timer1Count = 2
ITimer0: millis() = 10287
ITimer1: millis() = 10289
ITimer0: millis() = 12287
ITimer0: millis() = 14287
ITimer1: millis() = 15289
ITimer0: millis() = 16287
ITimer0: millis() = 18287
Time = 20002, Timer0Count = 10, Timer1Count = 4
Changing Interval, Timer0 = 4000, Timer1 = 10000
ITimer0: millis() = 24002
ITimer0: millis() = 28002
ITimer1: millis() = 30002
Time = 30003, Timer0Count = 12, Timer1Count = 5
ITimer0: millis() = 32002
ITimer0: millis() = 36002
ITimer0: millis() = 40002
ITimer1: millis() = 40002
Time = 40004, Timer0Count = 15, Timer1Count = 6
Changing Interval, Timer0 = 2000, Timer1 = 5000
ITimer0: millis() = 42004
ITimer0: millis() = 44004
ITimer1: millis() = 45004
ITimer0: millis() = 46004
ITimer0: millis() = 48004
ITimer0: millis() = 50004
ITimer1: millis() = 50004
Time = 50005, Timer0Count = 20, Timer1Count = 8
ITimer0: millis() = 52004
ITimer0: millis() = 54004
ITimer1: millis() = 55004
ITimer0: millis() = 56004
ITimer0: millis() = 58004
ITimer0: millis() = 60004
ITimer1: millis() = 60004
Time = 60006, Timer0Count = 25, Timer1Count = 10
Changing Interval, Timer0 = 4000, Timer1 = 10000
ITimer0: millis() = 64006
ITimer0: millis() = 68006
ITimer1: millis() = 70006
Time = 70007, Timer0Count = 27, Timer1Count = 11
ITimer0: millis() = 72006
ITimer0: millis() = 76006
ITimer0: millis() = 80006
ITimer1: millis() = 80006
Time = 80008, Timer0Count = 30, Timer1Count = 12
Changing Interval, Timer0 = 2000, Timer1 = 5000
ITimer0: millis() = 82008
ITimer0: millis() = 84008
ITimer1: millis() = 85008
ITimer0: millis() = 86008
ITimer0: millis() = 88008
ITimer0: millis() = 90008
ITimer1: millis() = 90008
Time = 90009, Timer0Count = 35, Timer1Count = 14
ITimer0: millis() = 92008
ITimer0: millis() = 94008
ITimer1: millis() = 95008
ITimer0: millis() = 96008
ITimer0: millis() = 98008
ITimer0: millis() = 100008
ITimer1: millis() = 100008
Time = 100010, Timer0Count = 40, Timer1Count = 16
Changing Interval, Timer0 = 4000, Timer1 = 10000
ITimer0: millis() = 104010
ITimer0: millis() = 108010
ITimer1: millis() = 110010
Time = 110011, Timer0Count = 42, Timer1Count = 17
ITimer0: millis() = 112010
ITimer0: millis() = 116010
ITimer0: millis() = 120010
ITimer1: millis() = 120010
Time = 120012, Timer0Count = 45, Timer1Count = 18