DMA programming examples

AN4104

10/13

Doc ID 023131 Rev 1

3

DMA programming examples

The DMA firmware driver is provided with a set of examples, so you can quickly become

familiar with the DMA peripheral. It demonstrates how to use the DMA in different modes.

Both the package and the application note are available for download from the

STMicroelectronics website: http://www.st.com.

3.1

ADC DMA transfer to TIM example

This example provides a description of how to use a DMA channel to transfer continuously a

data from a peripheral (ADC) to another peripheral (TIM) supporting DMA transfer. The ADC

is configured to operate in Continuous Conversion mode. TIM is configured to generate a

PWM signal on its output.

The dedicated DMA channel is configured to transfer in circular mode the last ADC channel

converted value to the TIMER Capture/Compare register. The DMA channel request is

driven by the TIM update event. The duty cycle of TIMER channel output signal is then

changed each time the input voltage value on ADC channel pin is modified.

The duty cycle variation can be visualized on oscilloscope while changing the analog input

on ADC channel using the potentiometer.

3.2

DMA Flash to RAM example

This example illustrates how to use the DMA to transfer data between two memory

locations.

It provides a description of how to transfer a word data buffer located in Flash memory to

embedded SRAM memory using DMA channel.

DMA Channel is configured to transfer the contents of a 32-word data buffer stored in Flash

memory to the reception buffer declared in RAM.

The start of transfer is triggered by software. DMA Channel memory-to-memory transfer is

enabled. Source and destination addresses incrementing is also enabled.

The transfer is started by setting the Channel enable bit for DMA Channel. At the end of the

transfer, a Transfer Complete interrupt is generated since it is enabled. Once interrupt is

generated, the remaining data to be transferred is read which must be equal to 0 (DMA

Counter reaches 0 if all Data are transferred). The Transfer Complete Interrupt pending bit is

then cleared.

A comparison between the source and destination buffers is done to check that all data have

been correctly transferred.

3.3

DMA RAM to DAC example

This example provides a description of how to use a DMA channel to transfer data buffer

from memory (RAM memory) to the peripheral DAC.

The DMA channel is configured to transfer continuously, word by word, a Half-word buffer

from the RAM memory to the DAC register DAC_DHR12R. The DAC channel conversion is