NRF52_TimerInterrupt Library

khoih-prog · November 3, 2020, 5:07am

How To Install Using Arduino Library Manager

This library enables you to use Interrupt from Hardware Timers on an nRF52-based board. It 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 NRF52_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, 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:

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.
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.

Releases v1.0.0

Permit up to 16 super-long-time, super-accurate ISR-based timers to avoid being blocked
Using cpp code besides Impl.h code to use if Multiple-Definition linker error.

Supported Boards

AdaFruit Feather nRF52832, nRF52840 Express, BlueFruit Sense, Itsy-Bitsy nRF52840 Express, Metro nRF52840 Express, NINA_B302_ublox, NINA_B112_ublox etc..

Examples:

khoih-prog · November 3, 2020, 5:08am

Debug Termimal Output Samples

The following is the sample terminal output when running example ISR_Timer_Complex_Ethernet on Adafruit NRF52840_FEATHER EXPRESS using W5500 Ethernet to demonstrate the accuracy of ISR Hardware Timer, especially when system is very busy. The ISR timer is programmed for 2s, is activated exactly after 2.000s !!!

While software timer, programmed for 2s, is activated after 4.867s !!!. Then in loop(), it's also activated every 3s.

Starting ISR_Timer_Complex_Ethernet on NRF52840_FEATHER
Version : 1.0.0
NRF52TimerInterrupt: F_CPU (MHz) = 64, Timer = NRF_TIMER2
NRF52TimerInterrupt: _fre = 1000000.00, _count = 50000
Starting  ITimer OK, millis() = 1419
[1419] Getting IP...
[1419] MAC: FE-BE-97-DA-C3-EA
_pinCS = 0
W5100 init, using SS_PIN_DEFAULT = 10, new ss_pin = 10, W5100Class::ss_pin = 10
W5100::init: W5500, SSIZE =4096
[3104] IP:192.168.2.129
[3104] 
    ___  __          __
   / _ )/ /_ _____  / /__
  / _  / / // / _ \/  '_/
 /____/_/\_, /_//_/_/\_\
        /___/ v0.6.1 on ARDUINO_NRF52_ADAFRUIT

[3106] BlynkArduinoClient.connect: Connecting to account.duckdns.org:8080
[3218] Ready (ping: 8ms).
IP = 192.168.2.129
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 4867
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
2s: Delta ms = 2000
5s: Delta ms = 5000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
5s: Delta ms = 5000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
5s: Delta ms = 5000
2s: Delta ms = 2000
11s: Delta ms = 11000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
5s: Delta ms = 5000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
5s: Delta ms = 5000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
11s: Delta ms = 11000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
5s: Delta ms = 5000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
2s: Delta ms = 2000
5s: Delta ms = 5000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
21s: Delta ms = 21000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
11s: Delta ms = 11000
5s: Delta ms = 5000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
5s: Delta ms = 5000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000
2s: Delta ms = 2000
5s: Delta ms = 5000
11s: Delta ms = 11000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3000

The following is the sample terminal output when running exampleTimerInterruptTest on Adafruit NRF52840_ITSYBITSY to demonstrate the accuracy and how to start/stop Hardware Timers.

Starting TimerInterruptTest on NRF52840_ITSYBITSY
Version : 1.0.0
NRF52TimerInterrupt: F_CPU (MHz) = 64, Timer = NRF_TIMER1
NRF52TimerInterrupt: _fre = 1000000.00, _count = 1000000
Starting  ITimer1 OK, millis() = 834
NRF52TimerInterrupt: F_CPU (MHz) = 64, Timer = NRF_TIMER2
NRF52TimerInterrupt: _fre = 1000000.00, _count = 3000000
Starting  ITimer1 OK, millis() = 835
ITimer0: millis() = 1834, delta = 1000
ITimer0: millis() = 2834, delta = 1000
ITimer0: millis() = 3834, delta = 1000
ITimer1: millis() = 3835, delta = 3000
ITimer0: millis() = 4834, delta = 1000
Stop ITimer0, millis() = 5001
ITimer1: millis() = 6835, delta = 3000
ITimer1: millis() = 9835, delta = 3000
Start ITimer0, millis() = 10002
ITimer0: millis() = 11002, delta = 1000
ITimer0: millis() = 12002, delta = 1000
ITimer1: millis() = 12835, delta = 3000
ITimer0: millis() = 13002, delta = 1000
ITimer0: millis() = 14002, delta = 1000
Stop ITimer1, millis() = 15001
ITimer0: millis() = 15002, delta = 1000
Stop ITimer0, millis() = 15003
Start ITimer0, millis() = 20004
ITimer0: millis() = 21004, delta = 1000
ITimer0: millis() = 22004, delta = 1000
ITimer0: millis() = 23004, delta = 1000
ITimer0: millis() = 24004, delta = 1000
ITimer0: millis() = 25004, delta = 1000
Stop ITimer0, millis() = 25005
Start ITimer1, millis() = 30002
Start ITimer0, millis() = 30006
ITimer0: millis() = 31006, delta = 1000
ITimer0: millis() = 32006, delta = 1000
ITimer1: millis() = 33002, delta = 3000
ITimer0: millis() = 33006, delta = 1000
ITimer0: millis() = 34006, delta = 1000
ITimer0: millis() = 35006, delta = 1000
Stop ITimer0, millis() = 35007
ITimer1: millis() = 36002, delta = 3000
ITimer1: millis() = 39002, delta = 3000
Start ITimer0, millis() = 40008
ITimer0: millis() = 41008, delta = 1000
ITimer1: millis() = 42002, delta = 3000
ITimer0: millis() = 42008, delta = 1000
ITimer0: millis() = 43008, delta = 1000
ITimer0: millis() = 44008, delta = 1000
ITimer1: millis() = 45002, delta = 3000
Stop ITimer1, millis() = 45003
ITimer0: millis() = 45008, delta = 1000
Stop ITimer0, millis() = 45009
Start ITimer0, millis() = 50010
ITimer0: millis() = 51010, delta = 1000
ITimer0: millis() = 52010, delta = 1000
ITimer0: millis() = 53010, delta = 1000
ITimer0: millis() = 54010, delta = 1000
ITimer0: millis() = 55010, delta = 1000

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NRF52_TimerInterrupt Library

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