TIM DMA Burst transfer example

  ******************** (C) COPYRIGHT 2014 STMicroelectronics *******************
  * @file    TIM/TIM_DMABurst/readme.txt 
  * @author  MCD Application Team
  * @version V1.4.0
  * @date    24-July-2014
  * @brief   Description of the TIM DMA Burst transfer 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 update the TIM1 channel1 period and the duty cycle using the TIM DMA burst feature.

Every update DMA request, the DMA will do 3 transfers of half words into Timer registers beginning from ARR register. On the DMA update request, 0x0FFF will be transferred into ARR, 0x0000 will be transferred into RCR, 0x0555 will be transferred into CCR1.

The TIM1CLK frequency is set to SystemCoreClock (Hz), to get TIM1 counter clock at 24 MHz the Prescaler is computed as following:

• Prescaler = (TIM1CLK / TIM1 counter clock) - 1

SystemCoreClock is set to 48 MHz.

The TIM1 period is 5.8 KHz: TIM1 Frequency = TIM1 counter clock/(ARR + 1) = 24 MHz / 4096 = 5.8 KHz

The TIM1 CCR1 register value is equal to 0x555, so the TIM1 Channel 1 generates a PWM signal with a frequency equal to 5.8 KHz and a duty cycle equal to 33.33%: TIM1 Channel1 duty cycle = (TIM1_CCR1/ TIM1_ARR + 1)* 100 = 33.33%

The PWM waveform can be displayed using an oscilloscope.

Directory contents

• TIM/TIM_DMABurst/stm32f0xx_conf.h Library Configuration file
• TIM/TIM_DMABurst/stm32f0xx_it.c Interrupt handlers
• TIM/TIM_DMABurst/stm32f0xx_it.h Interrupt handlers header file
• TIM/TIM_DMABurst/main.c Main program
• TIM/TIM_DMABurst/main.h Header for main.c module
• TIM/TIM_DMABurst/system_stm32f0xx.c STM32F0xx system source file

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 the following pins to an oscilloscope to monitor the different waveforms:
    • TIM1 CH1 (PA.08)

• STM32072B-EVAL Set-up
  • Connect the following pins to an oscilloscope to monitor the different waveforms:
    • TIM1 CH1 (PA.08)

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
• Select the appropriate workspace
• Rebuild all files and load your image into target memory
• Run the example

© COPYRIGHT STMicroelectronics