- Important Note for Arduino IDE
- Why do we need this Dx_Slow_PWM library
- Changelog
- Prerequisites
- Installation
- HOWTO Fix
Multiple DefinitionsLinker Error - More useful Information
- Usage
- Examples
- Example ISR_8_PWMs_Array_Complex
- Debug Terminal Output Samples
- Debug
- Troubleshooting
- Issues
- TO DO
- DONE
- Contributions and Thanks
- Contributing
- License
- Copyright
With some Arduino IDE versions, such as v1.8.19, upload directly via USB to some boards, such as Curiosity_AVR128DA48 or Curiosity_AVR128DB48 can't be done without unknown-to-me fix. We'll get the following error when uploading
avrdude: Version 6.3-20201216
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2014 Joerg Wunsch
System wide configuration file is "/home/kh/.arduino15/packages/DxCore/hardware/megaavr/1.4.10/avrdude.conf"
User configuration file is "/home/kh/.avrduderc"
User configuration file does not exist or is not a regular file, skipping
Using Port : usb
Using Programmer : curiosity_updi
avrdude: usbdev_open(): Found nEDBG CMSIS-DAP, serno: MCHP3280041800002682
avrdude: usbdev_open(): WARNING: failed to set configuration 1: Device or resource busy
avrdude: Found CMSIS-DAP compliant device, using EDBG protocol
avrdude: usbdev_send(): wrote -5 out of 912 bytes, err = Input/output error
avrdude: jtag3_edbg_prepare(): failed to send command to serial port
avrdude done. Thank you.
the selected serial port
does not exist or your board is not connected
We can use drag-and-drop method to drag-and-drop the compiled hex file to CURIOSITY virtual drive.
If success, The LED blinks slowly for 2 sec. The LED will blinks rapidly for 2 sec if failure
For example, to run Change_Interval example, use Arduino IDE to compile, and get the Change_Interval.ino.hex file. For Ubuntu Linux, the file is stored in directory /tmp/arduino_build_xxxxxx
After drag-and-drop the Change_Interval.ino.hex into CURIOSITY virtual drive, the code will run immediately if successfully loaded (LED blinks slowly)
Why do we need this Dx_Slow_PWM library
This library enables you to use ISR-based PWM channels on Arduino AVRDx-based boards (AVR128Dx, AVR64Dx, AVR32Dx, etc.), using DxCore, to create and output PWM any GPIO pin. Because this library doesn't use the powerful purely hardware-controlled PWM with many limitations, the maximum PWM frequency is currently limited at 1000Hz, which is still suitable for many real-life applications. Now you can change the PWM settings on-the-fly
This library enables you to use Interrupt from Hardware Timers on AVRDx-based boards to create and output PWM to pins. It now supports 64 ISR-based synchronized PWM channels, while consuming only 1 Hardware Timer. PWM interval can be very long (uint64_t microsecs / millisecs). The most important feature is they're ISR-based PWM channels. Therefore, their executions are not blocked by bad-behaving functions or tasks. This important feature is absolutely necessary for mission-critical tasks. These hardware PWM channels, 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 PWM using millis() or micros(). That's necessary if you need to measure some data requiring better accuracy.
As Hardware Timers are rare, and very precious assets of any board, this library now enables you to use up to 64 ISR-based synchronized PWM channels, while consuming only 1 Hardware Timer. Timers' interval is very long (ulong millisecs).
Now with these new 64 ISR-based PWM-channels, the maximum interval is practically unlimited (limited only by unsigned long milliseconds) while the accuracy is nearly perfect compared to software PWM channels.
The most important feature is they're ISR-based PWM channels. Therefore, their executions are not blocked by bad-behaving functions / tasks. This important feature is absolutely necessary for mission-critical tasks.
The ISR_8_PWMs_Array_Complex example will demonstrate the nearly perfect accuracy, compared to software PWM, by printing the actual period / duty-cycle in microsecs of each of PWM-channels.
Being ISR-based PWM, their executions are not blocked by bad-behaving functions / tasks, such as connecting to WiFi, Internet or Blynk services. You can also have many (up to 64) PWM channels to use.
This non-being-blocked important feature is absolutely necessary for mission-critical tasks.
You'll see software-based SimpleTimer 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
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 PWM channels, 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 PWM channels using millis() or micros(). That's necessary if you need to measure some data requiring better accuracy.
Functions using normal software PWM channels, 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:
- AVRDA-based boards (AVR128DA, AVR64DA, AVR32DA, etc.) using DxCore
- AVRDB-based boards (AVR128DB, AVR64DB, AVR32DB, etc.) using DxCore
- AVRDD-based boards (AVR64DB, AVR32DB, AVR16DB, etc.) using DxCore v1.5.1+
-
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.
-
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.
Arduino IDE 1.8.19+for Arduino.SpenceKonde DxCore core 1.5.1+for Arduino AVRDx boards.. Follow DxCore Installation.
- To use with certain example
SimpleTimer libraryfor ISR_8_PWMs_Array_Simple and ISR_8_PWMs_Array_Complex examples.
The best and easiest way is to use Arduino Library Manager. Search for Dx_Slow_PWM, then select / install the latest version.
You can also use this link
Another way to install is to:
- Navigate to Dx_Slow_PWM page.
- Download the latest release
Dx_Slow_PWM-main.zip. - Extract the zip file to
Dx_Slow_PWM-maindirectory - Copy whole
Dx_Slow_PWM-mainfolder to Arduino libraries' directory such as~/Arduino/libraries/.
- Install VS Code
- Install PlatformIO
- Install Dx_Slow_PWM library by using Library Manager. Search for Dx_Slow_PWM in Platform.io Author's Libraries
- 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
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 this .hpp file
// Can be included as many times as necessary, without `Multiple Definitions` Linker Error
#include "Dx_Slow_PWM.hpp" //https://github.com/khoih-prog/Dx_Slow_PWMin 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 "Dx_Slow_PWM.h" //https://github.com/khoih-prog/Dx_Slow_PWMCheck the new multiFileProject example for a HOWTO demo.
Have a look at the discussion in Different behaviour using the src_cpp or src_h lib #80
- Arduino 101: Timers and Interrupts
- Getting Started with Timer/Counter Type B (TCB)
- DXCore README.md
- AVR128DA48-Curiosity-Nano-Hardware-User Guide
- AVR128DB48-Curiosity-Nano-Hardware-User Guide
TCB0-TCB4 are 16-bit timers
The AVRDx boards with 14, 20, 28 or 32 pins, such as AVRDx28, will have only 3 TCB timers, (TCB0-TCB2)
The AVRDx with 48 pins, such as Curiosity Nano AVRDA48, Curiosity Nano AVRDB48, will have 4 TCB timers, (TCB0-TCB3)
The AVRDx with 64 pins, such as AVRDA64, AVRDB64, will have 5 TCB timers, (TCB0-TCB4)
The number of TCB timers will be automatically configured by the library.
Before using any Timer, you have to make sure the Timer has not been used by any other purpose.
// Select USING_FULL_CLOCK == true for 24/16MHz to Timer TCBx => shorter timer, but better accuracy
// Select USING_HALF_CLOCK == true for 12/ 8MHz to Timer TCBx => shorter timer, but better accuracy
// Select USING_250KHZ == true for 250KHz to Timer TCBx => longer timer, but worse accuracy
// Not select for default 250KHz to Timer TCBx => longer timer, but worse accuracy
#define USING_FULL_CLOCK true
#define USING_HALF_CLOCK false
#define USING_250KHZ false // Not supported now
#define USE_TIMER_0 false
#define USE_TIMER_1 true
#define USE_TIMER_2 false // Normally used by millis(). Don't use
#define USE_TIMER_3 false
#define USE_TIMER_4 false
#if USE_TIMER_0
#define CurrentTimer ITimer0
#elif USE_TIMER_1
#define CurrentTimer ITimer1
#elif USE_TIMER_2
#define CurrentTimer ITimer2
#elif USE_TIMER_3
#define CurrentTimer ITimer3
#elif USE_TIMER_4
#define CurrentTimer ITimer4
#else
#error You must select one Timer
#endif
// Init Dx_Slow_PWM, each can service 64 different ISR-based PWM channels
Dx_Slow_PWM ISR_PWM;void irqCallbackStartFunc()
{
}
void irqCallbackStopFunc()
{
}
void setup()
{
....
// You can use this with PWM_Freq in Hz
ISR_PWM.setPWM(PWM_Pin, PWM_Freq, PWM_DutyCycle, irqCallbackStartFunc, irqCallbackStopFunc);
....
} - ISR_8_PWMs_Array
- ISR_8_PWMs_Array_Complex
- ISR_8_PWMs_Array_Simple
- ISR_Changing_PWM
- ISR_Modify_PWM
- multiFileProject New
Example ISR_8_PWMs_Array_Complex
The following is the sample terminal output when running example ISR_8_PWMs_Array_Complex Curiosity Nano AVR128DB48 to demonstrate how to use multiple PWM channels with complex callback functions, the accuracy of ISR Hardware PWM-channels, especially when system is very busy. The ISR PWM-channels is running exactly according to corresponding programmed periods and duty-cycles
Starting ISR_8_PWMs_Array_Complex on AVR128DB
Dx_Slow_PWM v1.1.0
CPU Frequency = 24 MHz
TCB Clock Frequency = Full clock (24/16MHz, etc) for highest accuracy
Starting ITimer1 OK, micros() = 13691
SimpleTimer (us): 2000, us : 10073297, Dus : 10058568
PWM Channel : 0, prog Period (ms): 1000.00, actual : 1000015, prog DutyCycle : 5, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual : 500025, prog DutyCycle : 10, actual : 10.00
PWM Channel : 2, prog Period (ms): 333.33, actual : 333348, prog DutyCycle : 20, actual : 19.98
PWM Channel : 3, prog Period (ms): 250.00, actual : 250042, prog DutyCycle : 30, actual : 29.98
PWM Channel : 4, prog Period (ms): 200.00, actual : 200046, prog DutyCycle : 40, actual : 39.98
PWM Channel : 5, prog Period (ms): 166.67, actual : 166671, prog DutyCycle : 45, actual : 44.98
PWM Channel : 6, prog Period (ms): 142.86, actual : 142908, prog DutyCycle : 50, actual : 49.98
PWM Channel : 7, prog Period (ms): 125.00, actual : 125018, prog DutyCycle : 55, actual : 54.94
SimpleTimer (us): 2000, us : 20140201, Dus : 10066904
PWM Channel : 0, prog Period (ms): 1000.00, actual : 1000014, prog DutyCycle : 5, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual : 500022, prog DutyCycle : 10, actual : 10.00
PWM Channel : 2, prog Period (ms): 333.33, actual : 333347, prog DutyCycle : 20, actual : 19.99
PWM Channel : 3, prog Period (ms): 250.00, actual : 250040, prog DutyCycle : 30, actual : 29.98
PWM Channel : 4, prog Period (ms): 200.00, actual : 200047, prog DutyCycle : 40, actual : 39.98
PWM Channel : 5, prog Period (ms): 166.67, actual : 166671, prog DutyCycle : 45, actual : 44.98
PWM Channel : 6, prog Period (ms): 142.86, actual : 142908, prog DutyCycle : 50, actual : 49.98
PWM Channel : 7, prog Period (ms): 125.00, actual : 125027, prog DutyCycle : 55, actual : 54.94
SimpleTimer (us): 2000, us : 30207240, Dus : 10067039
PWM Channel : 0, prog Period (ms): 1000.00, actual : 1000014, prog DutyCycle : 5, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual : 500024, prog DutyCycle : 10, actual : 10.00
PWM Channel : 2, prog Period (ms): 333.33, actual : 333347, prog DutyCycle : 20, actual : 19.99
PWM Channel : 3, prog Period (ms): 250.00, actual : 250041, prog DutyCycle : 30, actual : 29.98
PWM Channel : 4, prog Period (ms): 200.00, actual : 200045, prog DutyCycle : 40, actual : 39.98
PWM Channel : 5, prog Period (ms): 166.67, actual : 166680, prog DutyCycle : 45, actual : 44.98
PWM Channel : 6, prog Period (ms): 142.86, actual : 142918, prog DutyCycle : 50, actual : 49.98
PWM Channel : 7, prog Period (ms): 125.00, actual : 125028, prog DutyCycle : 55, actual : 54.93
...The following is the sample terminal output when running example ISR_8_PWMs_Array on AVR128DB to demonstrate how to use multiple PWM channels with simple callback functions.
Starting ISR_8_PWMs_Array on AVR128DB
Dx_Slow_PWM v1.1.0
CPU Frequency = 24 MHz
TCB Clock Frequency = Full clock (24/16MHz, etc) for highest accuracy
Starting ITimer1 OK, micros() = 12894The following is the sample terminal output when running example ISR_8_PWMs_Array_Simple on AVR128DB to demonstrate how to use multiple PWM channels.
Starting ISR_8_PWMs_Array_Simple on AVR128DB
Dx_Slow_PWM v1.1.0
CPU Frequency = 24 MHz
TCB Clock Frequency = Full clock (24/16MHz, etc) for highest accuracy
Starting ITimer1 OK, micros() = 14169The following is the sample terminal output when running example ISR_Modify_PWM on AVR128DB to demonstrate how to modify PWM settings on-the-fly without deleting the PWM channel
Starting ISR_Modify_PWM on AVR128DB
Dx_Slow_PWM v1.1.0
CPU Frequency = 24 MHz
TCB Clock Frequency = Full clock (24/16MHz, etc) for highest accuracy
Starting ITimer1 OK, micros() = 12823
Using PWM Freq = 2.00, PWM DutyCycle = 10.00The following is the sample terminal output when running example ISR_Changing_PWM on AVR128DB to demonstrate how to modify PWM settings on-the-fly by deleting the PWM channel and reinit the PWM channel
Starting ISR_Changing_PWM on AVR128DB
Dx_Slow_PWM v1.1.0
CPU Frequency = 24 MHz
TCB Clock Frequency = Full clock (24/16MHz, etc) for highest accuracy
Starting ITimer1 OK, micros() = 12998
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Using PWM Freq = 2.00, PWM DutyCycle = 90.00Debug is enabled by default on Serial.
You can also change the debugging level _PWM_LOGLEVEL_ from 0 to 4
// Don't define _PWM_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
#define _PWM_LOGLEVEL_ 0If 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.
Submit issues to: Dx_Slow_PWM issues
- Search for bug and improvement
- Basic hardware multi-channel PWM for AVRDx-based boards (AVR128Dx, AVR64Dx, AVR32Dx, etc.) using DxCore
- Add Table of Contents
- Add functions to modify PWM settings on-the-fly
- Fix
multiple-definitionslinker error - Optimize library code by using
reference-passinginstead ofvalue-passing - Improve accuracy by using
float, instead ofuint32_tfordutycycle - DutyCycle to be optionally updated at the end current PWM period instead of immediately.
- Display informational warning only when
_PWM_LOGLEVEL_> 3 9 MakeMAX_NUMBER_CHANNELSconfigurable to max 64 PWM channels - Remove debug codes possibly causing hang
- Improve debug to use
Serialxport automatically according to boards. - Add support to AVRDD (AVR64DD, AVR32DD, AVR16DD, etc.)
- Modify to use either breaking DxCore v1.5.1+ or v1.4.10-
Many thanks for everyone for bug reporting, new feature suggesting, testing and contributing to the development of this library. Especially to these people who have directly or indirectly contributed to this Dx_TimerInterrupt library
- Thanks to good work of Spence Konde (aka Dr. Azzy) for the DxCore and megaTinyCore
- Thanks to LaurentR59 to request
- the enhancement Support for DX CORE CPU and MightyCORE CPU possible? #8 leading to this new library
- the enhancement PWM to drive over 16 channels #1 leading to new v1.0.1
 ⭐️⭐️ Spence Konde |
 LaurentR59 |
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
- The library is licensed under MIT
Copyright (c) 2022- Khoi Hoang
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