- Important Note for Arduino IDE
- Why do we need this ATtiny_Slow_PWM library
- Changelog
- Prerequisites
- Installation
- HOWTO Fix
Multiple Definitions
Linker 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 AVR_CuriosityNano3217
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/megaTinyCore/hardware/megaavr/2.5.11/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: MCHP3333021800000998
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, or 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 ATtiny_Slow_PWM library
This library enables you to use ISR-based PWM channels on Arduino AVR ATtiny-based boards (ATtiny3217, etc.) using megaTinyCore, to create and output PWM any GPIO pin. Because this library doesn't use the powerful, high-speed, 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, such as LED lighting, Servo, etc. Now you can change the PWM settings on-the-fly
This library enables you to use Interrupt from Hardware Timers on AVR ATtiny-based boards to create and output PWM to any 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 uint64_t
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, such as connecting to WiFi, Internet or Blynk services. This important feature is absolutely necessary for mission-critical tasks. 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.
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.
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:
- tinyAVR boards using megaTinyCore
-
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 megaTinyCore core 2.6.4+
for Arduino ATtiny boards.. Follow megaTinyCore Installation.
- To use with certain example
SimpleTimer library
for 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 ATtiny_Slow_PWM, then select / install the latest version.
You can also use this link for more detailed instructions.
Another way to install is to:
- Navigate to ATtiny_Slow_PWM page.
- Download the latest release
ATtiny_Slow_PWM-main.zip
. - Extract the zip file to
ATtiny_Slow_PWM-main
directory - Copy whole
ATtiny_Slow_PWM-main
folder to Arduino libraries' directory such as~/Arduino/libraries/
.
- Install VS Code
- Install PlatformIO
- Install ATtiny_Slow_PWM library by using Library Manager. Search for ATtiny_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 "ATtiny_Slow_PWM.hpp" //https://github.com/khoih-prog/ATtiny_Slow_PWM
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 "ATtiny_Slow_PWM.h" //https://github.com/khoih-prog/ATtiny_Slow_PWM
Check 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)
- megaTinyCore README.md
- ATtiny3217 Curiosity Nano Hardware User Guide
- AVR128DA48-Curiosity-Nano-Hardware-User Guide
- AVR128DB48-Curiosity-Nano-Hardware-User Guide
TCB0-TCB1 are 16-bit timers
The ATtiny boards, such as ATtiny3217
, ATtiny1617
, will have only maximum 2 TCB timers, (TCB0-TCB1).
The ATtiny boards, such as ATtiny817
, will have only maximum 1 TCB timer, (TCB0).
The number of TCB timers will be automatically configured by the library.
The following is the partial list of number of TCBs for each ATtiny board/chip
ATtiny3217, ATtiny1617, ATtiny3216, ATtiny1616, ATtiny1614
ATtinyx12, ATtinyx14, ATtinyx16, ATtinyx17, such as ATtiny817, ATtiny417, ATtiny816, etc.
ATtinyx02, ATtinyx04, ATtinyx06, ATtinyx07, such as ATtiny1607, ATtiny807, ATtiny1606, etc.
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 20/16MHz to Timer TCBx => shorter timer, but better accuracy
// Select USING_HALF_CLOCK == true for 10/ 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
// Try to use RTC, TCA0 or TCD0 for millis()
#define USE_TIMER_0 true // Check if used by millis(), Servo or tone()
#define USE_TIMER_1 false // Check if used by millis(), Servo or tone()
#if USE_TIMER_0
#define CurrentTimer ITimer0
#elif USE_TIMER_1
#define CurrentTimer ITimer1
#else
#error You must select one Timer
#endif
// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error
#include "ATtiny_Slow_PWM.h"
// Init AT_TINY_SLOW_PWM, each can service max 64 different ISR-based PWM channels
AT_TINY_SLOW_PWM_ISR 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 AVR_ATtiny3217 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 AVR_ATtiny3217
ATtiny_Slow_PWM v1.0.0
CPU Frequency = 20 MHz
Max number PWM channels = 16
TCB Clock Frequency = Full clock (20/16MHz, etc) for highest accuracy
Starting ITimer OK, micros() = 15569
[PWM] Frequency = 1.00
[PWM] Frequency = 2.00
[PWM] Frequency = 3.00
[PWM] Frequency = 4.00
[PWM] Frequency = 5.00
[PWM] Frequency = 6.00
[PWM] Frequency = 7.00
[PWM] Frequency = 8.00
SimpleTimer (us): 2000, us : 7889400, Dus : 7868891
PWM Channel : 0, prog Period (ms): 1000.00, actual : 1000065, prog DutyCycle : 5, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual : 500018, prog DutyCycle : 10, actual : 9.99
PWM Channel : 2, prog Period (ms): 333.33, actual : 333369, prog DutyCycle : 20, actual : 19.99
PWM Channel : 3, prog Period (ms): 250.00, actual : 249361, prog DutyCycle : 30, actual : 30.06
PWM Channel : 4, prog Period (ms): 200.00, actual : 199999, prog DutyCycle : 40, actual : 39.97
PWM Channel : 5, prog Period (ms): 166.67, actual : 166717, prog DutyCycle : 45, actual : 44.95
PWM Channel : 6, prog Period (ms): 142.86, actual : 142904, prog DutyCycle : 50, actual : 49.94
PWM Channel : 7, prog Period (ms): 125.00, actual : 125031, prog DutyCycle : 55, actual : 54.95
SimpleTimer (us): 2000, us : 15209668, Dus : 7320268
PWM Channel : 0, prog Period (ms): 1000.00, actual : 1000067, prog DutyCycle : 5, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual : 500047, prog DutyCycle : 10, actual : 9.99
PWM Channel : 2, prog Period (ms): 333.33, actual : 333331, prog DutyCycle : 20, actual : 19.99
PWM Channel : 3, prog Period (ms): 250.00, actual : 175834, prog DutyCycle : 30, actual : 42.64
PWM Channel : 4, prog Period (ms): 200.00, actual : 200075, prog DutyCycle : 40, actual : 39.96
PWM Channel : 5, prog Period (ms): 166.67, actual : 166723, prog DutyCycle : 45, actual : 44.97
PWM Channel : 6, prog Period (ms): 142.86, actual : 142909, prog DutyCycle : 50, actual : 49.96
PWM Channel : 7, prog Period (ms): 125.00, actual : 125073, prog DutyCycle : 55, actual : 54.96
SimpleTimer (us): 2000, us : 22983887, Dus : 7774219
PWM Channel : 0, prog Period (ms): 1000.00, actual : 1000031, prog DutyCycle : 5, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual : 500018, prog DutyCycle : 10, actual : 9.99
PWM Channel : 2, prog Period (ms): 333.33, actual : 333332, prog DutyCycle : 20, actual : 19.99
PWM Channel : 3, prog Period (ms): 250.00, actual : 250023, prog DutyCycle : 30, actual : 29.99
PWM Channel : 4, prog Period (ms): 200.00, actual : 200032, prog DutyCycle : 40, actual : 39.97
PWM Channel : 5, prog Period (ms): 166.67, actual : 166716, prog DutyCycle : 45, actual : 44.95
PWM Channel : 6, prog Period (ms): 142.86, actual : 142865, prog DutyCycle : 50, actual : 49.98
PWM Channel : 7, prog Period (ms): 125.00, actual : 125062, prog DutyCycle : 55, actual : 54.98
...
The following is the sample terminal output when running example ISR_8_PWMs_Array on AVR_ATtiny3217 to demonstrate how to use multiple PWM channels with simple callback functions.
Starting ISR_8_PWMs_Array on AVR_ATtiny3217
ATtiny_Slow_PWM v1.0.0
CPU Frequency = 20 MHz
Max number PWM channels = 16
TCB Clock Frequency = Full clock (20/16MHz, etc) for highest accuracy
Starting ITimer OK, micros() = 14778
[PWM] Frequency = 1.00
[PWM] Frequency = 2.00
[PWM] Frequency = 3.00
[PWM] Frequency = 4.00
[PWM] Frequency = 5.00
[PWM] Frequency = 6.00
[PWM] Frequency = 7.00
[PWM] Frequency = 8.00
The following is the sample terminal output when running example ISR_8_PWMs_Array_Simple on AVR_ATtiny3217 to demonstrate how to use multiple PWM channels.
Starting ISR_8_PWMs_Array_Simple on AVR_ATtiny3217
ATtiny_Slow_PWM v1.0.0
CPU Frequency = 20 MHz
Max number PWM channels = 16
TCB Clock Frequency = Full clock (20/16MHz, etc) for highest accuracy
Starting ITimer OK, micros() = 15609
[PWM] Frequency = 1.00
[PWM] Frequency = 2.00
[PWM] Frequency = 3.00
[PWM] Frequency = 4.00
[PWM] Frequency = 5.00
[PWM] Frequency = 6.00
[PWM] Frequency = 7.00
[PWM] Frequency = 8.00
The following is the sample terminal output when running example ISR_Modify_PWM on AVR_ATtiny3217 to demonstrate how to modify PWM settings on-the-fly without deleting the PWM channel
Starting ISR_Modify_PWM on AVR_ATtiny3217
ATtiny_Slow_PWM v1.0.0
CPU Frequency = 20 MHz
Max number PWM channels = 16
TCB Clock Frequency = Full clock (20/16MHz, etc) for highest accuracy
Starting ITimer OK, micros() = 14755
Using PWM Freq = 2.00, PWM DutyCycle = 10.00
Modify Freq => 1.00, DC => 5.55
Modify Freq => 2.00, DC => 10.00
Modify Freq => 1.00, DC => 5.55
Modify Freq => 2.00, DC => 10.00
Modify Freq => 1.00, DC => 5.55
Modify Freq => 2.00, DC => 10.00
Modify Freq => 1.00, DC => 5.55
Modify Freq => 2.00, DC => 10.00
Modify Freq => 1.00, DC => 5.55
Modify Freq => 2.00, DC => 10.00
Modify Freq => 1.00, DC => 5.55
Modify Freq => 2.00, DC => 10.00
Modify Freq => 1.00, DC => 5.55
Modify Freq => 2.00, DC => 10.00
Modify Freq => 1.00, DC => 5.55
Modify Freq => 2.00, DC => 10.00
Modify Freq => 1.00, DC => 5.55
Modify Freq => 2.00, DC => 10.00
The following is the sample terminal output when running example ISR_Changing_PWM on AVR_ATtiny3217 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 AVR_ATtiny3217
ATtiny_Slow_PWM v1.0.0
CPU Frequency = 20 MHz
Max number PWM channels = 16
TCB Clock Frequency = Full clock (20/16MHz, etc) for highest accuracy
Starting ITimer OK, micros() = 14769
PWM Freq = 1.00, DC = 50.00
PWM Freq = 2.00, DC = 90.00
PWM Freq = 1.00, DC = 50.00
PWM Freq = 2.00, DC = 90.00
PWM Freq = 1.00, DC = 50.00
PWM Freq = 2.00, DC = 90.00
PWM Freq = 1.00, DC = 50.00
PWM Freq = 2.00, DC = 90.00
PWM Freq = 1.00, DC = 50.00
PWM Freq = 2.00, DC = 90.00
PWM Freq = 1.00, DC = 50.00
PWM Freq = 2.00, DC = 90.00
PWM Freq = 1.00, DC = 50.00
PWM Freq = 2.00, DC = 90.00
PWM Freq = 1.00, DC = 50.00
PWM Freq = 2.00, DC = 90.00
PWM Freq = 1.00, DC = 50.00
PWM Freq = 2.00, DC = 90.00
PWM Freq = 1.00, DC = 50.00
PWM Freq = 2.00, DC = 90.00
PWM Freq = 1.00, DC = 50.00
PWM Freq = 2.00, DC = 90.00
Debug 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_ 0
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.
Submit issues to: ATtiny_Slow_PWM issues
- Search for bug and improvement
- Add support to AVR ATtiny-based boards (ATtiny3217, etc.) using megaTinyCore
- Basic hardware multi-channel PWM for AVR ATtiny-based boards (ATtiny3217, etc.) using megaTinyCore
- Add Table of Contents
- Add functions to modify PWM settings on-the-fly
- Fix
multiple-definitions
linker error - Optimize library code by using
reference-passing
instead ofvalue-passing
- Improve accuracy by using
float
, instead ofuint32_t
fordutycycle
- DutyCycle to be optionally updated at the end current PWM period instead of immediately.
- Display informational warning only when
_PWM_LOGLEVEL_
> 3 - Make
MAX_NUMBER_CHANNELS
configurable to max 64 PWM channels - Remove debug codes possibly causing hang
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 megaTinyCore
- Thanks to LaurentR59 to request
- the enhancement Support for DX CORE CPU and MightyCORE CPU possible? #8 leading to this new library
![]() ⭐️⭐️ 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