STM32F0xx Standard Peripherals Firmware Library: COMP2 Pulse width measurement example

STM32F0xx Standard Peripherals Library

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COMP2 Pulse width measurement example 
  ******************** (C) COPYRIGHT 2014 STMicroelectronics *******************
  * @file    COMP/PulseWidthMeasurement/readme.txt 
  * @author  MCD Application Team
  * @version V1.4.0
  * @date    24-July-2014
  * @brief   Description of the COMP2 Pulse width measurement example.
  ******************************************************************************
  *
  * Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");
  * You may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *        http://www.st.com/software_license_agreement_liberty_v2
  *
  * Unless required by applicable law or agreed to in writing, software 
  * distributed under the License is distributed on an "AS IS" BASIS, 
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
  ******************************************************************************
Example Description

This example shows how to configure the COMP2 peripheral to measure pulse width. This method (measuring signal pulse using comparator is interesting when external signal doesn't respect the VIL and VIH levels).

  • COMP2 is configured as follow:
    • Inverting input is internally connected to DAC1 output
    • Non Inverting input is connected to PA1
    • Output is internally connected to TIM2 Input Capture 4 (IC4)
  • DAC channel 1 is used as a digital threshold for measurement, DAC1 output is internally connected to COMP1 inverting input. DAC1 is configured in 12-bit right alignment. DAC1 output = VREF * DOR / 4095 = 3.3 * 2000 / 4095 = 1.61V

In this example, the pulse of an external signal of around 1.6V (e.g. high level = 1.7V and low level = 1.5V) can be performed.

  • TIM2 counter is clocked by TIM2CLK = 48MHz, TIM2 channel 4 is configured in input capture mode. TIM2 counter is captured at each transition detection: rising or falling edges (each time COMP2 inverting input crosses DAC1 output)
  • External signal should be connected to PA1. Pulse is computed in microsecond then displayed on Color LCD for STM320518-EVAL. Pulse duration shouldn't be higher than 65535 * TIM2CLK = 2.047 ms Pulse duration shouldn't be lower than TIM2 ISR processing time / TIM2CLK ~ 110 (clock cycle) / 48 MHz = 2.3 us
Directory contents
Note:
The "system_stm32f0xx.c" is generated by an automatic clock configuration tool and can be easily customized to meet user application requirements. To select different clock setup, use the "STM32F0xx_Clock_Configuration_VX.Y.Z.xls" provided with the AN4055 package available on ST Microcontrollers
Hardware and Software environment
  • This example runs on STM32F0xx Devices.
  • This example has been tested with STMicroelectronics STM320518-EVAL and STM32072B-EVAL including respectively STM32F051R8T6 and STM32F072VBT6 devices and can be easily tailored to any other supported device and development board.
  • STM320518-EVAL Set-up
    • Connect an external signal to PA.01 pin.
  • STM32072B-EVAL Set-up
    • Connect an external signal to PA.01 pin.
How to use it ?

In order to make the program work, you must do the following :

  • Copy all source files from this example folder to the template folder under Project
  • Open your preferred toolchain
  • If the used device is STM32F051R8T6 choose STM32F051 project
    • Add the following files to the project source list
      • Utilities\STM32_EVAL\STM320518_EVAL\stm320518_eval.c
      • Utilities\STM32_EVAL\STM320518_EVAL\stm320518_eval_lcd.c
  • If the used device is STM32F072VBT6 choose STM32F072 project
    • Add the following files to the project source list
      • Utilities\STM32_EVAL\STM32072B_EVAL\stm32072b_eval.c
      • Utilities\STM32_EVAL\STM32072B_EVAL\stm32072b_eval_lcd.c
  • Rebuild all files and load your image into target memory
  • Run the example

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