Programming the DMA using the standard peripheral library

AN3117

14/28

Doc ID 16846 Rev 4

3.1.2

Selecting the channel request source

USARTx, SPIx, I2C1

Each communication peripheral (USARTx (x=1..3), SPIx (x=1,2) and I2C1) has two event

request sources: one for transmission (TX) and one for reception (RX).

Selection of the desired DMA request is performed by the driver of the communication

peripheral. Table 5 describes the DMA request configuration functions. Table 6 lists the

DMA channel allocation for the appropriate communication peripheral.

Note:

Refer to the stm8l15x_spi.h, stm8l15x_usart.h, and stm8l15x_i2c.h files for further details

about the SPI_DMACmd(), USART_DMACmd(), and I2C_DMACmd() functions and their

parameters.

Digital-to-analog convertor (DAC)

A DAC channel DMA request is generated when a software or hardware trigger occurs while

the trigger feature and the DAC DMA feature are enabled (using DAC_Init() and the

DAC_DMACmd() functions). The DAC channel DMA request remains set until a DAC

channel DMA acknowledge comes from the DMA controller. The DAC DMA request

indicates that DAC data holding registers have been transferred to the DAC data output

registers.

Table 5.

DMA request configuration functions from the communication peripheral

side

Peripheral

Function

Description

USARTx

USART_DMACmd()

Enables or disables the USART DMA requests. The

USARTx (x= 1...3) TX or RX requests are selected

independently.

SPIx

SPI_DMACmd()

Enables or disables the SPI DMA requests. The SPIx (x= 1,

2)TX or RX requests are selected independently.

I2C1

I2C_DMACmd()

Enables or disables the I2C DMA requests. Both I2C1 TX

and RX requests are selected.

Table 6.

Communication peripheral DMA channel allocations

Peripheral

RX request

TX request

USART1

DMA Ch.2

DMA Ch.1

USART2

DMA Ch.3

DMA Ch.0

USART3

DMA Ch.2

DMA Ch.1

SPI1

DMA Ch.1

DMA Ch.2

SPI2

DMA Ch.0

DMA Ch.3

I2C1

DMA Ch.0

DMA Ch.3