SLAAEN5 February   2025 MSPM0G1106 , MSPM0G1107 , MSPM0G1506 , MSPM0G1507 , MSPM0G1518 , MSPM0G1519 , MSPM0G3106 , MSPM0G3106-Q1 , MSPM0G3107 , MSPM0G3107-Q1 , MSPM0G3506 , MSPM0G3506-Q1 , MSPM0G3507 , MSPM0G3507-Q1 , MSPM0G3518 , MSPM0G3518-Q1 , MSPM0G3519 , MSPM0G3519-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Bridge between CAN and SPI
  5. 2Implementation
    1. 2.1 Principle
    2. 2.2 Structure
  6. 3Software Description
    1. 3.1 Software Functionality
    2. 3.2 Configurable Parameters
    3. 3.3 Structure of Custom Element
    4. 3.4 Structure of FIFO
    5. 3.5 SPI Receive and Transmit (Transparent Transmission)
    6. 3.6 SPI Receive and Transmit (Protocol Transmission)
    7. 3.7 CAN Receive and Transmit
    8. 3.8 Application Integration
  7. 4Hardware
  8. 5Application Aspects
    1. 5.1 Flexible structure
    2. 5.2 Optional Configuration for SPI
    3. 5.3 Optional Configuration for CAN
    4. 5.4 CAN Bus Multinode Communication Example
  9. 6Summary
  10. 7References

3.6 SPI Receive and Transmit (Protocol Transmission)

In general, SPI master controls the SPI communication, and SPI slave cannot trigger slave-to-master communication. In this design, another IO is used. The IO pull-down of the slave notifies the master that there is information to be sent. The user can modify the pin or remove the IO function as required.

For SPI receive, there are two global variables defined in bridge_spi.c.

uint8_t gSpiReceiveGroup[SPI_RX_SIZE];
Custom_Element gSPI_RX_Element;

The following is the process for SPI master reception An IO interrupt is used to detect the IO pull-down.

  1. In IO interrupt, call readSpiRxMsg() to send bytes to receive message from the SPI slave (SPIs send and receive together)
  2. Call getSpiRxMsg() to detect header and to store complete message into gSpiReceiveGroup.
  3. Call processSpiRxMsg () to extract information from gSpiReceiveGroup and store the data in gSPI_RX_Element.
  4. Place gSPI_RX_Element into gSpi2Can_FIFO.

The following is the process for SPI slave reception.

  1. Call getSpiRxMsg() to store message into gSpiReceiveGroup. Message reception is finished when timeout occurs.
  2. Call processSpiRxMsg() to extract data from gSpiReceiveGroup and store the data in gSPI_RX_Element.
  3. Put gSPI_RX_Element into gSpi2Can_FIFO.

For SPI transmission, there are two global variables defined in bridge_spi.c.

uint8_t gSpiTransmitGroup[SPI_TX_SIZE];
Custom_Element gSPI_TX_Element;

The following is the process for SPI master and slave transmission

  1. Get gSPI_TX_Element from gCan2Spi_FIFO.
  2. Call processSpiTxMsg() to obtain information from gSPI_TX_Element and store the data in gSpiTransmitGroup.
  3. Call sendSpiTxMsg() to transmit gSpiTransmitGroup through SPI.
  4. (SPI slave only) Use an IO to trigger the master to read from the slave.