/**
@page TIM_PWMOutput TIM example
@verbatim
******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
* @file Examples_LL/TIM/TIM_PWMOutput/readme.txt
* @author MCD Application Team
* @brief Description of the TIM_PWMOutput example.
******************************************************************************
* @attention
*
* Copyright (c) 2017 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
@endverbatim
@par Example Description
This example describes how to use a timer peripheral to generate a
PWM output signal and update PWM duty cycle;
Example using the STM32F4xx TIM LL API,
peripheral initialization done using LL unitary services functions
for optimization purpose (performance and size).
In this example TIM2 input clock TIM2CLK is set to APB1 clock (PCLK1),
since APB1 pre-scaler is equal to 1.
TIM2CLK = PCLK1
PCLK1 = HCLK
=> TIM2CLK = SystemCoreClock (100 MHz)
To set the TIM2 counter clock frequency to 10 KHz, the pre-scaler (PSC) is
calculated as follows:
PSC = (TIM2CLK / TIM2 counter clock) - 1
PSC = (SystemCoreClock /10 KHz) - 1
SystemCoreClock is set to 100 MHz for STM32F4xx Devices.
Auto-reload (ARR) is calculated to get a time base period of 10 ms,
meaning a time base frequency of 100 Hz.
ARR = (TIM2 counter clock / time base frequency) - 1
ARR = (TIM2 counter clock / 100) - 1
Initially, the capture/compare register (CCR1) of the output channel is set to
half the auto-reload value meaning a initial duty cycle of 50%.
Generally speaking this duty cycle is calculated as follows:
Duty cycle = (CCR1 / ARR) * 100
The timer output channel is mapped on the pin PA.05 (connected to LED2 on board
NUCLEO-F411RE). Thus LED2 status (on/off) mirrors the timer output
level (active v.s. inactive).
User push-button can be used to change the duty cycle from 0% up to 100% by
steps of 10%. Duty cycle is periodically measured. It can be observed through
the debugger by watching the variable uwMeasuredDutyCycle.
Initially the output channel is configured in output compare toggle mode.
@note The LED2 is not toggling. In fact, if the dutycycle is 0% so the LED2 is OFF. When pushing
successively the user button, the LED2 is ON and its luminosity rises as the dutycycle value keep
increasing.
@par Keywords
Timers, Output, signal, PWM, Oscilloscope, Frequency, Duty cycle, Waveform
@par Directory contents
- TIM/TIM_PWMOutput/Inc/stm32f4xx_it.h Interrupt handlers header file
- TIM/TIM_PWMOutput/Inc/main.h Header for main.c module
- TIM/TIM_PWMOutput/Inc/stm32_assert.h Template file to include assert_failed function
- TIM/TIM_PWMOutput/Src/stm32f4xx_it.c Interrupt handlers
- TIM/TIM_PWMOutput/Src/main.c Main program
- TIM/TIM_PWMOutput/Src/system_stm32f4xx.c STM32F4xx system source file
@par Hardware and Software environment
- This example runs on STM32F411xx devices.
- This example has been tested with NUCLEO-F411RE board and can be
easily tailored to any other supported device and development board.
@par How to use it ?
In order to make the program work, you must do the following :
- Open your preferred toolchain
- Rebuild all files and load your image into target memory
- Run the example
*/
3d6be4bd40