Transmit And Receive - GDMA

This sample demonstrates the functionality of sending and receiving data via CAN using GDMA.

The CAN controller is connected to a USB CAN analyser and communicates with the CAN controller by sending and receiving standard data frames, extended data frames, standard remote frames, extended remote frames and other frame types through the PC side.

The chip side receives the data from the PC via GDMA and transmits the same data to the PC side via GDMA and the PC side receives the data back from the chip.

Requirements

For requirements, please refer to the Requirements.

Wiring

The EVB is connected to a TJA1051 CAN Receiver module by connecting P3_2 to CTX, P3_4 to CRX. The EVB VCC3.3V is connected to the module VCC. The EVB GND is connected to the module GND.

The other end of the TJA1051 CAN Receiver module is connected to the PC via a USB CAN analyzer, by connecting module CANH to analyzer CANH and module CANL to analyzer CANL.

The hardware connection diagram is as follows:

CAN Hardware Connection Diagram

The introduction of CAN transceiver can refer to CAN Transceiver Introduction.

Building and Downloading

For building and downloading, please refer to the Building and Downloading.

Experimental Verification

1. After the IC is reset, a data frame sent by the IC is received on the tool.

2. The IC prints the log waiting to be received:

   [CAN]  start can trx_gdma demo!
   [CAN]  BUS state: 0, waiting...
   [CAN]  BUS ON 1
   [TX DMA HANDLER]  TX DONE!
   [CAN]  waiting for rx...
   

3. Send a data frame using the tool.

4. The IC receives the data frame via GDMA and prints log.

   [CAN HANDLER]  CAN RX
   [CAN HANDLER]  MB_1 rx done
   [RX DMA HANDLER]  GDMA_Channel_Handler
   [RX DMA HANDLER]  std id = 0x00000100, ext id = 0x00000000 dlc = 8
   [RX DMA HANDLER]  rx_data [0] 0x01
   [RX DMA HANDLER]  rx_data [1] 0x23
   [RX DMA HANDLER]  rx_data [2] 0x45
   [RX DMA HANDLER]  rx_data [3] 0x67
   [RX DMA HANDLER]  rx_data [4] 0x89
   [RX DMA HANDLER]  rx_data [5] 0xab
   [RX DMA HANDLER]  rx_data [6] 0xcd
   [RX DMA HANDLER]  rx_data [7] 0xef
   [CAN]  waiting for rx...
   

Code Overview

This section introduces the code and process description for initialization and corresponding function implementation in the sample.

Source Code Directory

The directory for project file and source code are as follows:

• Project directory: sdk\samples\peripheral\adc\continuous_gdma\proj

• Source code directory: sdk\samples\peripheral\adc\continuous_gdma\src

Initialization

The initialization flow for peripherals can refer to Initialization Flow in General Introduction.

1. Call Pad_Config() and Pinmux_Config() to configure the corresponding pin's PAD and PINMUX.

   void can_board_init(void)
   {
       /* Config pinmux and pad for CAN. */
   
       Pinmux_Config(CAN_TX_PIN, CAN_TX);
       Pinmux_Config(CAN_RX_PIN, CAN_RX);
   
       Pad_Config(CAN_TX_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_DISABLE, PAD_OUT_LOW);
       Pad_Config(CAN_RX_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_DISABLE, PAD_OUT_LOW);
   }
   

2. Call RCC_PeriphClockCmd() to enable the CAN clock.

3. Initialize the CAN peripheral:

   1. Define a CAN_InitTypeDef type init_struct and call CAN_StructInit() to pre-fill init_struct with default values.

   2. Modify the init_struct parameters as needed. The CAN initialization parameters are configured as shown in the table below.

   3. Call CAN_Init() to initialize the parameters and the CAN peripheral.

CAN Initialization Parameters

CAN Hardware Parameters	Setting in the init_struct	CAN
Auto Re-transmit Enable	CAN_InitTypeDef::CAN_AutoReTxEn	DISABLE
CAN speed parameter - brp	CAN_BIT_TIMING_TYPE_TypeDef::can_brp	3
CAN speed parameter - sjw	CAN_BIT_TIMING_TYPE_TypeDef::can_sjw	3
CAN speed parameter - tseg1	CAN_BIT_TIMING_TYPE_TypeDef::can_tseg1	13
CAN speed parameter - tseg2	CAN_BIT_TIMING_TYPE_TypeDef::can_tseg2	4
Rx GDMA Enable	CAN_InitTypeDef::CAN_RxDmaEn	ENABLE

4. Call CAN_Cmd() to enable the corresponding CAN peripheral.

5. Call CAN_INTConfig() to configure the CAN receive complete CAN_RX_INT interrupt, transmit complete CAN_TX_INT interrupt, error interrupt CAN_ERROR_INT, etc. Configure NVIC, and refer to Interrupt Configuration for NVIC-related configurations.

6. Call CAN_GetBusState() to loop-check the CAN bus state and wait for the CAN bus to open.

   while (CAN_GetBusState() != CAN_BUS_STATE_ON)
   {
       __asm volatile
       (
           "nop    \n"
       );
   }
   

Note

If the program is stuck at the point of waiting for the CAN bus to be on, please check if the CAN bus is connected correctly.

7. Call RCC_PeriphClockCmd() to enable the GDMA clock.

8. Initialize the GDMA peripheral:

   1. Define a GDMA_InitTypeDef type GDMA_InitStruct and execute GDMA_StructInit() to pre-fill GDMA_InitStruct with default values.

   2. Modify the GDMA_InitStruct parameters as needed. The initialization parameter configuration for GDMA TX and RX channels is shown in the following table. Execute GDMA_Init() to initialize the GDMA peripheral.

   3. Configure the GDMA total transfer complete interrupt GDMA_INT_Transfer and NVIC. Refer to Interrupt Configuration for related NVIC configurations.

GDMA Initialization Parameters

GDMA Hardware Parameters	Setting in the GDMA_InitStruct	GDMA TX Channel	GDMA RX Channel
Channel Num	GDMA_InitTypeDef::GDMA_ChannelNum	1	0
Transfer Direction	GDMA_InitTypeDef::GDMA_DIR	GDMA_DIR_MemoryToMemory	GDMA_DIR_PeripheralToMemory
Buffer Size	GDMA_InitTypeDef::GDMA_BufferSize	sizeof(CAN_RAM_TypeDef)	-
Source Address Increment or Decrement	GDMA_InitTypeDef::GDMA_SourceInc	DMA_SourceInc_Inc	DMA_SourceInc_Fix
Destination Address Increment or Decrement	GDMA_InitTypeDef::GDMA_DestinationInc	DMA_DestinationInc_Inc	DMA_DestinationInc_Inc
Source Data Size	GDMA_InitTypeDef::GDMA_SourceDataSize	GDMA_DataSize_Word	GDMA_DataSize_Word
Destination Data Size	GDMA_InitTypeDef::GDMA_DestinationDataSize	GDMA_DataSize_Word	GDMA_DataSize_Word
Source Burst Transaction Length	GDMA_InitTypeDef::GDMA_SourceMsize	GDMA_Msize_8	GDMA_Msize_1
Destination Burst Transaction Length	GDMA_InitTypeDef::GDMA_DestinationMsize	GDMA_Msize_8	GDMA_Msize_1
Source Address	GDMA_InitTypeDef::GDMA_SourceAddr	-	& (CAN->CAN_RX_DMA_DATA)
Destination Address	GDMA_InitTypeDef::GDMA_DestinationAddr	(CAN->CAN_RAM_DATA)	-
Source Handshake	GDMA_InitTypeDef::GDMA_SourceHandshake	-	GDMA_Handshake_CAN_BUS_RX
Destination Handshake	GDMA_InitTypeDef::GDMA_DestHandshake	-	-

Note

During the initialization of the GDMA peripheral, do not initialize the source address of the TX GDMA channel and the destination address of the RX GDMA channel; these will be adjusted dynamically later.

Functional Implementation

1. Call the can_dma_tx function to configure the value tx_can_ram_struct that needs to be set in the RAM register via TX GDMA.

2. Call the can_start_tx_dma function.

   1. Set the source address of the TX GDMA channel to the address of tx_can_ram_struct.

   2. Enable the GDMA_INT_Transfer interrupt for TX GDMA.

   3. Enable the GDMA peripheral to start the transmission.

   void can_start_tx_dma(CAN_RAM_TypeDef *p_can_ram_data)
   {
       GDMA_SetSourceAddress(TX_GDMA_Channel, (uint32_t)p_can_ram_data);
       GDMA_INTConfig(TX_GDMA_CHANNEL_NUM, GDMA_INT_Transfer, ENABLE);
       GDMA_Cmd(TX_GDMA_CHANNEL_NUM, ENABLE);
   }
   

3. After enabling the GDMA TX channel, GDMA transfers data from tx_can_ram_struct to (CAN->CAN_RAM_DATA). When TX is completed, a GDMA TX interrupt is triggered, and relevant information is printed.

   GDMA_INTConfig(TX_GDMA_CHANNEL_NUM, GDMA_INT_Transfer, DISABLE);
   DBG_DIRECT("[TX GDMA HANDLER]  TX DONE!");
   GDMA_ClearINTPendingBit(TX_GDMA_CHANNEL_NUM, GDMA_INT_Transfer);
   

4. Call the can_dma_rx function.

   1. Mask the reception of frames rtr, ide, and id filtering, i.e., receive all frames.

   2. Enable Rx GDMA and disable automatic reply.

   3. Configure the message buffer to receive mode using the set reception frame type.

   4. Enable message buffer reception interrupt and wait for the RAM status to be idle.

   ...
   rx_frame_type.msg_buf_id = RX_DMA_BUF_ID;
   rx_frame_type.frame_rtr_mask = SET;
   rx_frame_type.frame_ide_mask = SET;
   rx_frame_type.frame_id_mask = CAN_FRAME_ID_MASK_MAX_VALUE;
   rx_frame_type.rx_dma_en = SET;
   rx_frame_type.auto_reply_bit = RESET;
   rx_error = CAN_SetMsgBufRxMode(&rx_frame_type);
   CAN_MBRxINTConfig(rx_frame_type.msg_buf_id, ENABLE);
   while (CAN_GetRamState() != CAN_RAM_STATE_IDLE)
   ...
   

5. When the message buffer reception is complete, execute the interrupt handler function CAN_Handler.

   1. Call the CAN_GetRxDmaMsize() function to obtain the Rx GDMA buffer size.

   2. Call the can_start_rx_dma function to enable the configuration of the GDMA buffer size, configure the destination address of the GDMA RX channel, and enable RX GDMA transmission.

   if (dma_en_flag == ENABLE)
   {
       uint32_t dma_buffer_size = CAN_GetRxDmaMsize();
       can_start_rx_dma((uint32_t)&rx_dma_data_struct, dma_buffer_size);
   }
   
   ...
   
   GDMA_SetBufferSize(RX_GDMA_Channel, buffer_size);
   GDMA_SetDestinationAddress(RX_GDMA_Channel, des_addr);
   GDMA_INTConfig(RX_GDMA_CHANNEL_NUM, GDMA_INT_Transfer, ENABLE);
   GDMA_Cmd(RX_GDMA_CHANNEL_NUM, ENABLE);
   

6. After enabling the GDMA RX channel, when CAN receives data, the GDMA transfers the data from &(CAN->CAN_RX_DMA_DATA) to rx_dma_data_struct. When the RX GDMA reception is complete, the interrupt handler function RX_GDMA_Channel_Handler is executed.

   1. Disable the GDMA_INT_Transfer interrupt for RX GDMA.

   2. Enable the RX GDMA of the message buffer to start the next reception.

   3. Print the received frame ID and print the received frame data.

   4. Clear the GDMA_INT_Transfer interrupt flag for RX GDMA.

   GDMA_INTConfig(RX_GDMA_CHANNEL_NUM, GDMA_INT_Transfer, DISABLE);
   ...
   CAN_SetMBnRxDmaEnFlag(RX_DMA_BUF_ID, ENABLE);
   ...
   DBG_DIRECT(...);
   ...
   GDMA_ClearINTPendingBit(RX_GDMA_CHANNEL_NUM, GDMA_INT_Transfer);
   

See Also

Please refer to the relevant API Reference:

• CAN

• PINMUX

• RCC