Module dma 

Available on crate feature unstable only.

Direct Memory Access (DMA)

Overview

The DMA driver provides an interface to efficiently transfer data between different memory regions and peripherals within the ESP microcontroller without involving the CPU. The DMA controller is responsible for managing these data transfers.

Notice, that this module is a common version of the DMA driver, ESP32 and ESP32-S2 are using older PDMA controller, whenever other chips are using newer GDMA controller.

Examples

Initialize and utilize DMA controller in SPI

let dma_channel = peripherals.DMA_CH0;
let sclk = peripherals.GPIO0;
let miso = peripherals.GPIO2;
let mosi = peripherals.GPIO4;
let cs = peripherals.GPIO5;

let mut spi = Spi::new(
    peripherals.SPI2,
    Config::default()
        .with_frequency(Rate::from_khz(100))
        .with_mode(Mode::_0),
)?
.with_sck(sclk)
.with_mosi(mosi)
.with_miso(miso)
.with_cs(cs)
.with_dma(dma_channel);

⚠️ Note: Descriptors should be sized as (max_transfer_size + CHUNK_SIZE - 1) / CHUNK_SIZE. I.e., to transfer buffers of size 1..=CHUNK_SIZE, you need 1 descriptor.

⚠️ Note: For chips that support DMA to/from PSRAM (ESP32-S3) DMA transfers to/from PSRAM have extra alignment requirements. The address and size of the buffer pointed to by each descriptor must be a multiple of the cache line (block) size. This is 32 bytes on ESP32-S3.

For convenience you can use the crate::dma_buffers macro.

Structs

AnyGdmaChannel

An arbitrary GDMA channel

AnyGdmaRxChannel

An arbitrary GDMA RX channel

AnyGdmaTxChannel

An arbitrary GDMA TX channel

BufView

An in-progress view into DmaRxBuf/DmaTxBuf.

Channel

DMA Channel

DmaDescriptor

A DMA transfer descriptor.

DmaDescriptorFlags

DMA descriptor flags.

DmaLoopBuf

DMA Loop Buffer

DmaRxBuf

DMA receive buffer

DmaRxStreamBuf

DMA Streaming Receive Buffer.

DmaRxStreamBufView

A view into a DmaRxStreamBuf

DmaRxTxBuf

DMA transmit and receive buffer.

DmaTransferRx

DMA transaction for RX only transfers

DmaTransferRxCircular

DMA transaction for RX only circular transfers

DmaTransferRxTx

DMA transaction for TX+RX transfers

DmaTransferTx

DMA transaction for TX only transfers

DmaTransferTxCircular

DMA transaction for TX only circular transfers

DmaTxBuf

DMA transmit buffer

EmptyBuf

An empty buffer that can be used when you don’t need to transfer any data.

Mem2Mem

DMA Memory to Memory pseudo-Peripheral

Mem2MemRx

The RX half of Mem2Mem.

Mem2MemRxTransfer

Represents an ongoing (or potentially finished) DMA Memory-to-Memory RX transfer.

Mem2MemTx

The TX half of Mem2Mem.

Mem2MemTxTransfer

Represents an ongoing (or potentially finished) DMA Memory-to-Memory TX transfer.

Preparation

Holds all the information needed to configure a DMA channel for a transfer.

SimpleMem2Mem

A simple and easy to use wrapper around SimpleMem2Mem. More complex memory to memory transfers should use Mem2Mem directly.

SimpleMem2MemTransfer

Represents an ongoing (or potentially finished) DMA Memory-to-Memory transfer.

Enums

BurstConfig

Burst transfer configuration.

DmaAlignmentError

DMA buffer alignment errors.

DmaBufError

Error returned from Dma[Rx|Tx|RxTx]Buf operations.

DmaError

DMA Errors

DmaInterrupt

Kinds of interrupt to listen to.

DmaPriority

DMA Priorities

DmaRxInterrupt

Types of interrupts emitted by the RX channel.

DmaTxInterrupt

Types of interrupts emitted by the TX channel.

Owner

The owner bit of a DMA descriptor.

TransferDirection

The direction of the DMA transfer.

Constants

CHUNK_SIZE

The default chunk size used for DMA transfers.

Traits

DmaChannel

A description of a DMA Channel.

DmaChannelFor

Trait implemented for DMA channels that are compatible with a particular peripheral.

DmaRxBuffer

DmaRxBuffer is a DMA descriptor + memory combo that can be used for receiving data from a peripheral’s FIFO to a DMA channel.

DmaRxChannel

Stability

DmaTxBuffer

DmaTxBuffer is a DMA descriptor + memory combo that can be used for transmitting data from a DMA channel to a peripheral’s FIFO.

DmaTxChannel

Stability

ReadBuffer

Trait for buffers that can be given to DMA for reading.

RxChannelFor

Trait implemented for the RX half of split DMA channels that are compatible with a particular peripheral. Accepts complete DMA channels or split halves.

TxChannelFor

Trait implemented for the TX half of split DMA channels that are compatible with a particular peripheral. Accepts complete DMA channels or split halves.

WriteBuffer

Trait for buffers that can be given to DMA for writing.

Functions

descriptor_count

Computes the number of descriptors required for a given buffer size with a given chunk size.

Type Aliases

PeripheralDmaChannel

Helper type to get the DMA (Rx and Tx) channel for a peripheral.

PeripheralRxChannel

Helper type to get the DMA Rx channel for a peripheral.

PeripheralTxChannel

Helper type to get the DMA Tx channel for a peripheral.