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HardwareTimer library
Warning
RequiresArduino_Core_STM32 version higher than 1.6.1
The HardwareTimer library aims to provide access to part of STM32 hardware Timer feature (If other features are required, they could be accessed throughSTM32Cube HAL/LL).
The use of this library suppose you have some basic knowledge of STM32 hardware timer architecture.First of all remind that all timers are not equivalent and doesn't support the same features. Please refer to the Reference Manual of your MCU.
Example:
TIM6andTIM7doesn't have outpin and this is the reason why, when available, they are used to implement Tone and Servo.- Some timers have up to 4 output channels with 4 complementary channelswhereas other timers have no complementary, or have only 1 or 2 channels...
Each timer may provide several channels, nevertheless it is important to understand that all channels of the same timer share the same counter and thus have the same period/frequency.
Warning
For genericity purpose, HardwareTimer library uses all timers like a 16bits timer (even if some may be wider).
voidpause(void);// Pause counter and all output channelsvoidpauseChannel(uint32_t channel);// Timer is still running but channel (output and interrupt) is disabledvoidresume(void);// Resume counter and all output channelsvoidresumeChannel(uint32_t channel);// Resume only one channelvoidsetPrescaleFactor(uint32_t prescaler);// set prescaler register (which is factor value - 1)uint32_tgetPrescaleFactor();voidsetOverflow(uint32_t val, TimerFormat_t format = TICK_FORMAT);// set AutoReload register depending on format provideduint32_tgetOverflow(TimerFormat_t format = TICK_FORMAT);// return overflow depending on format providedvoidsetPWM(uint32_t channel, PinName pin,uint32_t frequency,uint32_t dutycycle,callback_function_t PeriodCallback =nullptr,callback_function_t CompareCallback =nullptr);// Set all in one command freq in HZ, Duty in percentage. Including both interrupt.voidsetPWM(uint32_t channel,uint32_t pin,uint32_t frequency,uint32_t dutycycle,callback_function_t PeriodCallback =nullptr,callback_function_t CompareCallback =nullptr);voidsetCount(uint32_t val, TimerFormat_t format = TICK_FORMAT);// set timer counter to value 'val' depending on format provideduint32_tgetCount(TimerFormat_t format = TICK_FORMAT);// return current counter value of timer depending on format providedvoidsetMode(uint32_t channel, TimerModes_t mode, PinName pin = NC);// Configure timer channel with specified mode on specified pin if availablevoidsetMode(uint32_t channel, TimerModes_t mode,uint32_t pin); TimerModes_tgetMode(uint32_t channel);// Retrieve configured modevoidsetPreloadEnable(bool value);// Configure overflow preload enable settinguint32_tgetCaptureCompare(uint32_t channel, TimerCompareFormat_t format = TICK_COMPARE_FORMAT);// return Capture/Compare register value of specified channel depending on format providedvoidsetCaptureCompare(uint32_t channel,uint32_t compare, TimerCompareFormat_t format = TICK_COMPARE_FORMAT);// set Compare register value of specified channel depending on format providedvoidsetInterruptPriority(uint32_t preemptPriority,uint32_t subPriority);// set interrupt priority//Add interrupt to period updatevoidattachInterrupt(callback_function_t callback);// Attach interrupt callback which will be called upon update event (timer rollover)voiddetachInterrupt();// remove interrupt callback which was attached to update eventboolhasInterrupt();//returns true if a timer rollover interrupt has already been set//Add interrupt to capture/compare channelvoidattachInterrupt(uint32_t channel,callback_function_t callback);// Attach interrupt callback which will be called upon compare match event of specified channelvoiddetachInterrupt(uint32_t channel);// remove interrupt callback which was attached to compare match event of specified channelboolhasInterrupt(uint32_t channel);//returns true if an interrupt has already been set on the channel compare matchvoidtimerHandleDeinit();// Timer deinitialization// Refresh() is useful while timer is running after some registers updatevoidrefresh(void);// Generate update event to force all registers (Autoreload, prescaler, compare) to be taken into accountuint32_tgetTimerClkFreq();// return timer clock frequency in Hz.staticvoidcaptureCompareCallback(TIM_HandleTypeDef *htim);// Generic Capture and Compare callback which will call user callbackstaticvoidupdateCallback(TIM_HandleTypeDef *htim);// Generic Update (rollover) callback which will call user callback// The following function(s) are available for more advanced timer options TIM_HandleTypeDef *getHandle();// return the handle address for HAL related configurationuint32_tgetChannel(uint32_t channel);uint32_tgetLLChannel(uint32_t channel);uint32_tgetIT(uint32_t channel);uint32_tgetAssociatedChannel(uint32_t channel);#if defined(TIM_CCER_CC1NE)bool isComplementaryChannel[TIMER_CHANNELS];#endif
HardwareTimer is a C++ class, 1st thing to do is to instantiate an object withTIM instance as parameter.
Note
Some instances are used by Servo, Tone and SoftSerial (see TIMER_SERVO, TIMER_TONE and TIMER_SERIAL) but only when they are used. Just be sure there is no conflict with your own usage.
Example:
HardwareTimer *MyTim =new HardwareTimer(TIM3);// TIM3 is MCU hardware peripheral instance, its definition is provided in CMSIS
Then it is possible to configure mode of a channel.
Note
No need to configure pin mode (output/input/AlternateFunction), it will be done automatically by HardwareTimer library.
Note
Channel range [1..4], but not all timers support 4 channels.
Example:
MyTim->setMode(channel, TIMER_OUTPUT_COMPARE_PWM1, pin);Caution
Since core release 2.9.0:TIMER_DISABLED andTIMER_OUTPUT_COMPARE are obsolete and replaced byTIMER_OUTPUT_DISABLED.
Supported Mode:
typedefenum {TIMER_OUTPUT_DISABLED,// == TIM_OCMODE_TIMING no output, useful for only-interrupt// Output CompareTIMER_OUTPUT_COMPARE_ACTIVE,// == TIM_OCMODE_ACTIVE pin is set high when counter == channel compareTIMER_OUTPUT_COMPARE_INACTIVE,// == TIM_OCMODE_INACTIVE pin is set low when counter == channel compareTIMER_OUTPUT_COMPARE_TOGGLE,// == TIM_OCMODE_TOGGLE pin toggles when counter == channel compareTIMER_OUTPUT_COMPARE_PWM1,// == TIM_OCMODE_PWM1 pin high when counter < channel compare, low otherwiseTIMER_OUTPUT_COMPARE_PWM2,// == TIM_OCMODE_PWM2 pin low when counter < channel compare, high otherwiseTIMER_OUTPUT_COMPARE_FORCED_ACTIVE,// == TIM_OCMODE_FORCED_ACTIVE pin always highTIMER_OUTPUT_COMPARE_FORCED_INACTIVE,// == TIM_OCMODE_FORCED_INACTIVE pin always low//Input captureTIMER_INPUT_CAPTURE_RISING,// == TIM_INPUTCHANNELPOLARITY_RISINGTIMER_INPUT_CAPTURE_FALLING,// == TIM_INPUTCHANNELPOLARITY_FALLINGTIMER_INPUT_CAPTURE_BOTHEDGE,// == TIM_INPUTCHANNELPOLARITY_BOTHEDGE// Used 2 channels for a single pin. One channel in TIM_INPUTCHANNELPOLARITY_RISING another channel in TIM_INPUTCHANNELPOLARITY_FALLING.// Channels must be used by pair: CH1 with CH2, or CH3 with CH4// This mode is very useful for Frequency and Dutycycle measurementTIMER_INPUT_FREQ_DUTY_MEASUREMENT,TIMER_NOT_USED=0xFFFF// This must be the last item of this enum}TimerModes_t;
Then it is possible to configurePrescalerFactor. The Timer clock will be divided by this factor (if timer clock is 10Khz, and prescaler factor is 2, then timer will count at 5kHz).
Note
Configuration ofprescaler is automatic when using methodsetOverflow withformat == MICROSEC_FORMAT orformat == HERTZ_FORMAT.
Note
Prescaler is for timer counter and thus is common to all channel.
Note
PrescalerFactor range: [1.. 0x10000] (Hardware register will range [0..0xFFFF]).
Example:
MyTim->setPrescaleFactor(8);
Then it is possible to configureoverflow (also called rollover or update).
Foroutput it correspond to period or frequency.
Forinput capture it is suggested to use max value: 0x10000 to avoid rollover before capture occurs .
Note
Configuration ofprescaler is automatic when using methodsetOverflow withformat == MICROSEC_FORMAT orformat == HERTZ_FORMAT.
Note
overflow is common to all channel.
Note
Overflow range: [1.. 0x10000] (Hardware register will range [0..0xFFFF]).
Example:
MyTim->setOverflow(10000);// Default format is TICK_FORMAT. Rollover will occurs when timer counter counts 10000 ticks (it reach it count from 0 to 9999) MyTim->setOverflow(10000, TICK_FORMAT); MyTim->setOverflow(10000, MICROSEC_FORMAT);// 10000 microseconds MyTim->setOverflow(10000, HERTZ_FORMAT);// 10 kHz
Then it is possible to configureCaptureCompare (channel specific CaptureCompare register).
Note
CaptureCompare is for one channel only.
Note
CaptureCompare range: [0.. 0xFFFF]
Example:
MyTim->setCaptureCompare(channel,50);// Default format is TICK_FORMAT. 50 ticks MyTim->setCaptureCompare(channel,50, TICK_FORMAT) MyTim->setCaptureCompare(channel,50, MICROSEC_COMPARE_FORMAT);// 50 microseconds between counter reset and compare MyTim->setCaptureCompare(channel,50, HERTZ_COMPARE_FORMAT);// 50 Hertz -> 1/50 seconds between counter reset and compare MyTim->setCaptureCompare(channel,50, RESOLUTION_8B_COMPARE_FORMAT);// used for Dutycycle: [0.. 255] MyTim->setCaptureCompare(channel,50, RESOLUTION_12B_COMPARE_FORMAT);// used for Dutycycle: [0.. 4095]
It is possible to attach a user callback on update interrupt (rollover) and/or on Capture/Compare interrupt.If no channel is specified, the user callback is attach to update event.Note that the Update Interrupt Flag (UIF) is set when an update event occurs and generates an interrupt, and is automatically cleared by the HAL driverbefore the user callback is executed. There is no need for the user callback to clear the UIF explicitly.
Example:
MyTim->attachInterrupt(Update_IT_callback);// Userdefined call back. See 'Examples' chapter to see how to use callback with or without parameter MyTim->attachInterrupt(channel, Compare_IT_callback);// Userdefined call back. See 'Examples' chapter to see how to use callback with or without parameter
It is now time to start timer.
Note
All channel of the same timer are started at the same time (as there is only 1 counter per timer).
Example:
MyTim->resume();Timer can be paused then resumed
MyTim->pause(); ... MyTim->resume();
Below is an example of full PWM configuration.
Example:
MyTim->setMode(channel, TIMER_OUTPUT_COMPARE_PWM1, pin);// MyTim->setPrescaleFactor(8); // Due to setOverflow with MICROSEC_FORMAT, prescaler will be computed automatically based on timer input clock MyTim->setOverflow(100000, MICROSEC_FORMAT);// 10000 microseconds = 10 milliseconds MyTim->setCaptureCompare(channel,50, PERCENT_COMPARE_FORMAT);// 50% MyTim->attachInterrupt(Update_IT_callback); MyTim->attachInterrupt(channel, Compare_IT_callback); MyTim->resume();
To simplify basic PWM configuration, a dedicated all-in-one API is provided.Overflow/frequency is in hertz, dutycycle in percentage.
Example:
MyTim->setPWM(channel, pin,5,10,NULL,NULL);// No callback required, we can simplify the function call MyTim->setPWM(channel, pin,5,10);// 5 Hertz, 10% dutycycle
Some additional APIs allow to retrieve configurations:
getPrescaleFactor();getOverflow();getCaptureCompare();// In InputCapture mode, this method doesn't retrieve configuration but retrieve the captured counter valuegetCount();
Also, to get ride of Interrupt callback:
detachInterrupt()Note
Once the timer is started with the callback enabled you can disable and enable the callback throughdetachInterrupt andattachInterrupt freely, how many times you want. However, if the firstresume (= timer start) is done withoutbefore callingattachInterrupt, the HardwareTimer willnot be able to attach the interrupt later (for performance reasons the timer will be started with interrupts disabled)
If you detach and attach interrupts while the timer is running, starting from version 1.8.0, you can also know if there's a callback already attached (without the need to track it externally) through the method
hasInterrupt()Following examples are provided inSTM32Examples library (available with Arduino Library manager):
This example shows how to configure HardwareTimer to execute a callback at regular interval.Callback toggles pin.Once configured, there is only CPU load for callbacks executions.
Timebase_callback_with_parameter.ino
This example shows how to configure HardwareTimer to execute a callback with parameter at regular interval.Callback toggles pin.Once configured, there is only CPU load for callbacks executions.
This example shows how to fully configure a PWM with HardwareTimer.PWM is generated on
LED_BUILTINif available.PWM is generated by hardware: no CPU load.Nevertheless, in this example both interruption callback are used on Compare match (Falling edge of PWM1 mode) and update event (rising edge of PWM1 mode).Those call back are used to toggle a second pin:pin2.Once configured, there is only CPU load for callbacks executions.This example shows how to configure a PWM with HardwareTimer in one single function call.PWM is generated on
LED_BUILTINif available.No interruption callback used: PWM is generated by hardware.Once configured, there is no CPU load.This example shows how to configure HardwareTimer in inputcapture to measure external signal frequency.Each time a rising edge is detected on the input pin, hardware will save counter value into CaptureCompare register.External signal (signal generator for example) should be connected to
D2.Measured frequency is displayed on Serial Monitor.Frequency_Dutycycle_measurement.ino
This example shows how to configure HardwareTimer to measure external signal frequency and dutycycle.The input pin will be connected to 2 channel of the timer, one for rising edge the other for falling edge.Each time a rising edge is detected on the input pin, hardware will save counter value into one of the CaptureCompare register.Each time a falling edge is detected on the input pin, hardware will save counter value into the other CaptureCompare register.External signal (signal generator for example) should be connected to
D2.
Warning
RequiredArduino_Core_STM32 version higher than 1.6.1
Tone,Servo andanalogwrite have been updated to useHardwareTimer.
New optional parameterdestruct has been added tonoTone to decide whether to destruct/free HardwareTimer object.
noTone(uint8_t _pin,bool destruct =false)
There is a special case where period is set to its maximum value 0xFFFF and 100% duty cycle is requested.It is not possible to achieve this from hardware point of view (except changing mode toTIMER_OUTPUT_COMPARE_FORCED_ACTIVE).In this specific case there will be 1 tick (the last one) which will be LOW. Then we lose only 1 tick out of 65535 => 99,998..%