- Important Change from v1.2.0
- Why do we need this ESP8266_PWM library
- Changelog
- Prerequisites
- Installation
- HOWTO Fix
Multiple Definitions
Linker Error - More useful Information
- Examples
- Example ISR_16_PWMs_Array_Complex
- Debug Terminal Output Samples
- Debug
- Troubleshooting
- Issues
- TO DO
- DONE
- Contributions and Thanks
- Contributing
- License
- Copyright
Please have a look at HOWTO Fix Multiple Definitions
Linker Error
As more complex calculation and check inside ISR are introduced from v1.2.0, there is possibly some crash depending on use-case.
You can modify to use larger HW_TIMER_INTERVAL_US
, (from current 20uS), according to your board and use-case if crash happens.
// Current 20uS
#define HW_TIMER_INTERVAL_US 20L
Why do we need this ESP8266_PWM library
This library enables you to use Interrupt from Hardware Timers on an ESP8266-based board to create and output PWM to pins. The maximum PWM frequency is currently limited at 500Hz. Now you can also modify PWM settings on-the-fly.
This library enables you to use Interrupt from Hardware Timers on an ESP8266-based board to create and output PWM to pins. It now supports 16 ISR-based synchronized PWM channels, while consuming only 1 Hardware Timer. PWM interval can be very long (uint32_t 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 timers 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 16 ISR-based synchronized PWM channels, 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 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_16_PWMs_Array_Complex example will demonstrate the nearly perfect accuracy compared to software timers by printing the actual elapsed millisecs of each type of PWM channels.
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.
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 PWM-channels 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:
- ESP8266 boards, such as ESP8266_NODEMCU_ESP12E, etc.
-
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.
-
ESP8266 Core 3.0.2+
for ESP8266-based boards. -
SimpleTimer library
to use with some examples.
The best and easiest way is to use Arduino Library Manager
. Search for ESP8266_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 ESP8266_PWM page.
- Download the latest release
ESP8266_PWM-main.zip
. - Extract the zip file to
ESP8266_PWM-main
directory - Copy whole
ESP8266_PWM-main
folder to Arduino libraries' directory such as~/Arduino/libraries/
.
- Install VS Code
- Install PlatformIO
- Install ESP8266_PWM library by using Library Manager. Search for ESP8266_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 "ESP8266_PWM.hpp" //https://github.com/khoih-prog/ESP8266_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 "ESP8266_PWM.h" //https://github.com/khoih-prog/ESP8266_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
The ESP8266 timers are badly designed, using only 23-bit counter along with maximum 256 prescaler. They're only better than UNO / Mega. The ESP8266 has two hardware timers, but timer0 has been used for WiFi and it's not advisable to use. Only timer1 is available. The timer1's 23-bit counter terribly can count only up to 8,388,607. So the timer1 maximum interval is very short. Using 256 prescaler, maximum timer1 interval is only 26.843542 seconds !!!
The timer1 counters can be configured to support automatic reload.
Now with these new 16 ISR-based timers
, 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
- ISR_16_PWMs_Array
- ISR_16_PWMs_Array_Complex
- ISR_16_PWMs_Array_Simple
- ISR_Changing_PWM
- ISR_Modify_PWM
- multiFileProject New
Example ISR_16_PWMs_Array_Complex
The following is the sample terminal output when running example ISR_16_PWMs_Array_Complex to demonstrate 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
Starting ISR_16_PWMs_Array_Complex on ESP8266_NODEMCU_ESP12E
ESP8266_PWM v1.2.4
CPU Frequency = 160 MHz
[PWM] ESP8266TimerInterrupt: Timer Clock fre = 80000000
[PWM] Timer fre = 50000.00 , _count = 1600
Starting ITimer OK, micros() = 2073808
Channel : 0 Period : 1000000 OnTime : 50000 Start_Time : 2077435
Channel : 1 Period : 500000 OnTime : 50000 Start_Time : 2083470
Channel : 2 Period : 333333 OnTime : 66666 Start_Time : 2089512
Channel : 3 Period : 250000 OnTime : 75000 Start_Time : 2095588
Channel : 4 Period : 200000 OnTime : 80000 Start_Time : 2101657
Channel : 5 Period : 166666 OnTime : 74999 Start_Time : 2107738
Channel : 6 Period : 142857 OnTime : 71428 Start_Time : 2113805
Channel : 7 Period : 125000 OnTime : 68750 Start_Time : 2119875
SimpleTimer (ms): 2000, ms : 12126030, Dms : 10048756
PWM Channel : 0, programmed Period (us): 1000000.00, actual : 1000005, programmed DutyCycle : 5.00, actual : 5.00
PWM Channel : 1, programmed Period (us): 500000.00, actual : 500013, programmed DutyCycle : 10.00, actual : 10.00
PWM Channel : 2, programmed Period (us): 333333.34, actual : 333348, programmed DutyCycle : 20.00, actual : 20.00
PWM Channel : 3, programmed Period (us): 250000.00, actual : 250016, programmed DutyCycle : 30.00, actual : 29.99
PWM Channel : 4, programmed Period (us): 200000.00, actual : 200004, programmed DutyCycle : 40.00, actual : 39.99
PWM Channel : 5, programmed Period (us): 166666.67, actual : 166684, programmed DutyCycle : 45.00, actual : 44.99
PWM Channel : 6, programmed Period (us): 142857.14, actual : 142869, programmed DutyCycle : 50.00, actual : 49.99
PWM Channel : 7, programmed Period (us): 125000.00, actual : 125018, programmed DutyCycle : 55.00, actual : 54.99
SimpleTimer (ms): 2000, ms : 22199583, Dms : 10073553
PWM Channel : 0, programmed Period (us): 1000000.00, actual : 1000005, programmed DutyCycle : 5.00, actual : 5.00
PWM Channel : 1, programmed Period (us): 500000.00, actual : 500012, programmed DutyCycle : 10.00, actual : 10.00
PWM Channel : 2, programmed Period (us): 333333.34, actual : 333348, programmed DutyCycle : 20.00, actual : 20.00
PWM Channel : 3, programmed Period (us): 250000.00, actual : 250016, programmed DutyCycle : 30.00, actual : 29.99
PWM Channel : 4, programmed Period (us): 200000.00, actual : 200005, programmed DutyCycle : 40.00, actual : 39.99
PWM Channel : 5, programmed Period (us): 166666.67, actual : 166684, programmed DutyCycle : 45.00, actual : 44.99
PWM Channel : 6, programmed Period (us): 142857.14, actual : 142870, programmed DutyCycle : 50.00, actual : 49.99
PWM Channel : 7, programmed Period (us): 125000.00, actual : 125019, programmed DutyCycle : 55.00, actual : 54.99
SimpleTimer (ms): 2000, ms : 32273095, Dms : 10073512
PWM Channel : 0, programmed Period (us): 1000000.00, actual : 1000004, programmed DutyCycle : 5.00, actual : 5.00
PWM Channel : 1, programmed Period (us): 500000.00, actual : 500012, programmed DutyCycle : 10.00, actual : 10.00
PWM Channel : 2, programmed Period (us): 333333.34, actual : 333348, programmed DutyCycle : 20.00, actual : 20.00
PWM Channel : 3, programmed Period (us): 250000.00, actual : 250016, programmed DutyCycle : 30.00, actual : 29.99
PWM Channel : 4, programmed Period (us): 200000.00, actual : 200005, programmed DutyCycle : 40.00, actual : 39.99
PWM Channel : 5, programmed Period (us): 166666.67, actual : 166685, programmed DutyCycle : 45.00, actual : 44.99
PWM Channel : 6, programmed Period (us): 142857.14, actual : 142870, programmed DutyCycle : 50.00, actual : 49.99
PWM Channel : 7, programmed Period (us): 125000.00, actual : 125019, programmed DutyCycle : 55.00, actual : 54.99
The following is the sample terminal output when running example ISR_16_PWMs_Array to demonstrate how to use multiple Hardware PWM channels.
Starting ISR_16_PWMs_Array on ESP8266_NODEMCU_ESP12E
ESP8266_PWM v1.2.4
CPU Frequency = 160 MHz
[PWM] ESP8266TimerInterrupt: Timer Clock fre = 80000000
[PWM] Timer fre = 50000.00 , _count = 1600
Starting ITimer OK, micros() = 2072589
Channel : 0 Period : 1000000 OnTime : 50000 Start_Time : 2076168
Channel : 1 Period : 500000 OnTime : 50000 Start_Time : 2082485
Channel : 2 Period : 333333 OnTime : 66666 Start_Time : 2088818
Channel : 3 Period : 250000 OnTime : 75000 Start_Time : 2095149
Channel : 4 Period : 200000 OnTime : 80000 Start_Time : 2101479
Channel : 5 Period : 166667 OnTime : 75000 Start_Time : 2107820
Channel : 6 Period : 142857 OnTime : 71428 Start_Time : 2114152
Channel : 7 Period : 125000 OnTime : 68750 Start_Time : 2120482
The following is the sample terminal output when running example ISR_16_PWMs_Array_Simple to demonstrate how to use multiple Hardware PWM channels.
Starting ISR_16_PWMs_Array_Simple on ESP8266_NODEMCU_ESP12E
ESP8266_PWM v1.2.4
CPU Frequency = 160 MHz
[PWM] ESP8266TimerInterrupt: Timer Clock fre = 80000000
[PWM] Timer fre = 50000.00 , _count = 1600
Starting ITimer OK, micros() = 2073472
Channel : 0 Period : 1000000 OnTime : 50000 Start_Time : 2077055
Channel : 1 Period : 500000 OnTime : 50000 Start_Time : 2083379
Channel : 2 Period : 333333 OnTime : 66666 Start_Time : 2089704
Channel : 3 Period : 250000 OnTime : 75000 Start_Time : 2096036
Channel : 4 Period : 200000 OnTime : 80000 Start_Time : 2102366
Channel : 5 Period : 166667 OnTime : 75000 Start_Time : 2108707
Channel : 6 Period : 142857 OnTime : 71428 Start_Time : 2115038
Channel : 7 Period : 125000 OnTime : 68750 Start_Time : 2121369
The following is the sample terminal output when running example ISR_Modify_PWM to demonstrate how to modify PWM settings on-the-fly without deleting the PWM channel
Starting ISR_Modify_PWM on ESP8266_NODEMCU_ESP12E
ESP8266_PWM v1.2.4
CPU Frequency = 160 MHz
[PWM] ESP8266TimerInterrupt: Timer Clock fre = 80000000
[PWM] Timer fre = 50000.00 , _count = 1600
Starting ITimer OK, micros() = 2072681
Using PWM Freq = 200.00, PWM DutyCycle = 1.00
Channel : 0 Period : 5000 OnTime : 50 Start_Time : 2080334
Channel : 0 Period : 10000 OnTime : 555 Start_Time : 12082106
Channel : 0 Period : 5000 OnTime : 50 Start_Time : 22083353
Channel : 0 Period : 10000 OnTime : 555 Start_Time : 32084600
Channel : 0 Period : 5000 OnTime : 50 Start_Time : 42085847
Channel : 0 Period : 10000 OnTime : 555 Start_Time : 52087094
Channel : 0 Period : 5000 OnTime : 50 Start_Time : 62088341
Channel : 0 Period : 10000 OnTime : 555 Start_Time : 72089588
Channel : 0 Period : 5000 OnTime : 50 Start_Time : 82090835
Channel : 0 Period : 10000 OnTime : 555 Start_Time : 92092082
Channel : 0 Period : 5000 OnTime : 50 Start_Time : 102093328
Channel : 0 Period : 10000 OnTime : 555 Start_Time : 112094575
Channel : 0 Period : 5000 OnTime : 50 Start_Time : 122095822
Channel : 0 Period : 10000 OnTime : 555 Start_Time : 132097069
Channel : 0 Period : 5000 OnTime : 50 Start_Time : 142098316
Channel : 0 Period : 10000 OnTime : 555 Start_Time : 152099563
Channel : 0 Period : 5000 OnTime : 50 Start_Time : 162100810
Channel : 0 Period : 10000 OnTime : 555 Start_Time : 172102056
The following is the sample terminal output when running example ISR_Changing_PWM 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 ESP8266_NODEMCU_ESP12E
ESP8266_PWM v1.2.4
CPU Frequency = 160 MHz
[PWM] ESP8266TimerInterrupt: Timer Clock fre = 80000000
[PWM] Timer fre = 50000.00 , _count = 1600
Starting ITimer OK, micros() = 2073309
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Channel : 0 Period : 1000000 OnTime : 500000 Start_Time : 2080902
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Channel : 0 Period : 500000 OnTime : 450000 Start_Time : 12087445
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Channel : 0 Period : 1000000 OnTime : 500000 Start_Time : 22087762
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Channel : 0 Period : 500000 OnTime : 450000 Start_Time : 32088065
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Channel : 0 Period : 1000000 OnTime : 500000 Start_Time : 42088370
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Channel : 0 Period : 500000 OnTime : 450000 Start_Time : 52088673
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Channel : 0 Period : 1000000 OnTime : 500000 Start_Time : 62088982
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Channel : 0 Period : 500000 OnTime : 450000 Start_Time : 72089285
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Channel : 0 Period : 1000000 OnTime : 500000 Start_Time : 82089593
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Channel : 0 Period : 500000 OnTime : 450000 Start_Time : 92089898
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Channel : 0 Period : 1000000 OnTime : 500000 Start_Time : 102090204
Debug is enabled by default on Serial.
You can also change the debugging level _PWM_LOGLEVEL_
from 0 to 4
// These define's must be placed at the beginning before #include "ESP8266_PWM.h"
// _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_ 4
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: ESP8266_PWM issues
- Search for bug and improvement.
- Similar features for remaining Arduino boards such as SAMD21, SAMD51, SAM-DUE, nRF52, STM32, Portenta_H7, RP2040, etc.
- Basic hardware PWM-channels for ESP8266 for ESP8266 core v3.0.2+
- Longer time interval
- Add complex examples.
- Add functions to modify PWM settings on-the-fly
- Improve accuracy by using
float
, instead ofuint32_t
fordutycycle
- Optimize library code by using
reference-passing
instead ofvalue-passing
- DutyCycle to be optionally updated at the end current PWM period instead of immediately.
- Display informational warning only when
_PWM_LOGLEVEL_
> 3
Many thanks for everyone for bug reporting, new feature suggesting, testing and contributing to the development of this library.
- Thanks to AnselPeng2019 to request new feature to modify PWM settings on-the-fly in
- Change Duty Cycle #1 leading to v1.1.0
- Thanks to ggmichael to request better PWM resolution, leading to v1.2.0, in
and enhancement request as well as testing to verify, leading to v1.2.2, in
![]() AnselPeng2019 |
![]() ggmichael |
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 2021- Khoi Hoang