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diff --git a/Projects/NUCLEO-WB35CE/Examples/LPTIM/LPTIM_PWMExternalClock/readme.txt b/Projects/NUCLEO-WB35CE/Examples/LPTIM/LPTIM_PWMExternalClock/readme.txt new file mode 100644 index 000000000..8ddb63093 --- /dev/null +++ b/Projects/NUCLEO-WB35CE/Examples/LPTIM/LPTIM_PWMExternalClock/readme.txt @@ -0,0 +1,100 @@ +/** + @page LPTIM_PWMExternalClock LPTIM PWM External clock example + + @verbatim + ****************************************************************************** + * @file LPTIM/LPTIM_PWMExternalClock/readme.txt + * @author MCD Application Team + * @brief Description of the LPTIM PWM with an External clock example. + ****************************************************************************** + * + * Copyright (c) 2019 STMicroelectronics. All rights reserved. + * + * This software component is licensed by ST under BSD 3-Clause license, + * the "License"; You may not use this file except in compliance with the + * License. You may obtain a copy of the License at: + * opensource.org/licenses/BSD-3-Clause + * + ****************************************************************************** + @endverbatim + +@par Example Description + +How to configure and use, through the HAL LPTIM API, the LPTIM peripheral using an external counter clock, +to generate a PWM signal at the lowest power consumption. + +At the beginning of the main program the HAL_Init() function is called to reset +all the peripherals, initialize the Flash interface and the systick. +The SystemClock_Config() function is used to configure the system clock for STM32WB35CEUx Devices : +The CPU at 64 MHz + +The Autorelaod equal to 99 so the output frequency (OutputFrequency) will +be equal to the external counter clock (InputFrequency) divided by (99+1). + + OutputFrequency = InputFrequency / (Autoreload + 1) + = InputFrequency / 100 + +Pulse value equal to 49 and the duty cycle (DutyCycle) is computed as follow: + + DutyCycle = 1 - [(PulseValue + 1)/ (Autoreload + 1)] + DutyCycle = 50% + +To minimize the power consumption, after starting generating the PWM signal, +the MCU enters in STOP mode. Note that GPIOs are configured in Low Speed to +lower the consumption. + +User push-button (SW1) pin (PA.00)is configured as input with external interrupt (External line 0), +falling edge. When User push-button (SW1) is pressed, wakeup event is generated and PWM signal +generation is stopped. + +@note This example can not be used in DEBUG mode, this is due to the fact + that the Cortex-M4 core is no longer clocked during low power mode + so debugging features are disabled. + +@note Care must be taken when using HAL_Delay(), this function provides accurate + delay (in milliseconds) based on variable incremented in SysTick ISR. This + implies that if HAL_Delay() is called from a peripheral ISR process, then + the SysTick interrupt must have higher priority (numerically lower) + than the peripheral interrupt. Otherwise the caller ISR process will be blocked. + To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function. + +@note This example needs to ensure that the SysTick time base is always set to 1 millisecond + to have correct HAL operation. + + +@par Keywords + +Timer, Low Power, PWM, Stop mode, Interrupt, External Clock, Output, Duty Cycle + +@par Directory contents + + - LPTIM/LPTIM_PWMExternalClock/Inc/stm32wbxx_hal_conf.h HAL configuration file + - LPTIM/LPTIM_PWMExternalClock/Inc/stm32wbxx_it.h Interrupt handlers header file + - LPTIM/LPTIM_PWMExternalClock/Inc/main.h Header for main.c module + - LPTIM/LPTIM_PWMExternalClock/Src/stm32wbxx_it.c Interrupt handlers + - LPTIM/LPTIM_PWMExternalClock/Src/main.c Main program + - LPTIM/LPTIM_PWMExternalClock/Src/stm32wbxx_hal_msp.c HAL MSP module + - LPTIM/LPTIM_PWMExternalClock/Src/system_stm32wbxx.c STM32WBxx system source file + + +@par Hardware and Software environment + + - This example runs on STM32WB35CEUx devices. + + - This example has been tested with STMicroelectronics NUCLEO-WB35CE + board and can be easily tailored to any other supported device + and development board. + + - Connect a clock signal to PB5 (pin 21 in CN10 connector). + - Connect PB2 (pin 17 in CN10 connector) to an oscilloscope + to monitor the LPTIM output waveform. + +@par How to use it ? + +In order to make the program work, you must do the following : + - Open your preferred tool chain + - Rebuild all files and load your image into target memory + - Run the example + + * <h3><center>© COPYRIGHT STMicroelectronics</center></h3> + */ |