Spi User Guide


This document details AUTOSAR BSW SPI module implementation

  • Supported AUTOSAR Release : 4.3.1
  • Supported Configuration Variants : Post-build, Link-time, Pre-Compile
  • Vendor ID : SPI_VENDOR_ID (44)
  • Module ID : SPI_MODULE_ID (83)

The SPI driver provides services for basic communication with external components. These components can be used by an application. The main tasks of the SPI driver are:

  • Handle the SPI hardware units onboard – MCSPI
  • Handle data transmission to the components connected via SPI
  • Take care of the settings required by external components (baud rate etc.
  • DMA support has also been added to SPI module.

Spi Driver Architecture/Design

Please refer the SPI design, which is included as part of release (Spi Design Document)

Functional Description

The The Multi-channel Serial Peripheral Interface (MCSPI) is a master/slave synchronous serial bus. It allows a master device to initiate serial data transfers to a slave device.

Programming of clock source for the MCSPI, is beyond the scope of this document. The driver expects user of this module has programmed required clock source.

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Spi Instance ID mapping and ISR mapping

Please refer to the SOC User Manual for detail.

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The Spi Driver implementation supports multiple configuration variants (refer section Introduction), the driver expects generated Spi_Cfg.h to be present as (File Structure). Please refer (Build) to specify path to generated configuration. The associated MCSPI configuration generated files Spi_Cfg.c, Spi_Lcfg.c and Spi_PBcfg.c to be present as show (File Structure)

NOTE: Always use configurator tool for MCAL configuration generation.

The following section details on the un-supported features and additional features added.

Variance / Deviation from the specification


This parameter is the communication baudrate which allows using a range of values, from the point of view of configuration tools, from Hz up to MHz.This is achieved using modulespecific parameter SpiExtDeviceClockDivider


This parameter is the timing between clock and chip select (in seconds) This parameter allows to use a range of values from 0 up to 0.0001 seconds. Range specified by AUTOSAR specification is not supported by SPI hardware. TI specific SpiCsIdleTime parameter is used instead of this.

Implementation Specific Configurations

This driver implementation introduces below listed configurable options

Please refer the SPI design section NON Standard configurable parameters (Refer to Design Document provided in CSP), which is included as part of release (Spi Design Document)

Implementation Specific Configuration Constraint

This driver implementation introduces configurable constraint as mentioned below.

Please define all the SPI instances defined in SpiHwUnitType. Hw Unit Id 0 always corresponds to SPI_UNIT_MCU_MCSPI0.. and SPI_UNIT_MCSPI7 corresponds to 10. So to use SPI_UNIT_MCSPI1, user needs to define SPI_UNIT_MCU_MCSPI0 SPI_UNIT_MCU_MCSPI1 SPI_UNIT_MCU_MCSPI2 SPI_UNIT_MCSPI0.

Hw Unit Id SpiHwUnitType

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Non Standard Service APIs


As noted from the previous MCAL implementation, some of the critical configuration registers could potentially be corrupted by other entities (s/w or h/w). One of the recommended detection methods would be to periodically read-back the configuration and confirm configuration is consistent. The service API defined below shall be implemented to enable this detection

Description Comments
Service Name Spi_RegisterReadback Can potentially be turned OFF (Refer to Design Document provided in CSP)
Syntax uint32 Spi_RegisterReadback ( Spi_HWUnitType HWUnit, P2VAR(Spi_RegisterReadbackType, AUTOMATIC, SPI_APPL_DATA) RegRbPtr) E_OK: Register read back has been done, E_NOT_OK: Register read back failed
Service ID NA
Sync / Async Sync
Reentrancy Reentrant
Parameter in HWUnit SPI Hardware microcontroller peripheral unit ID. If this is invalid, then the API will return E_NOT_OK.
Parameters out RegRbPtr - Pointer to where to store the readback values. If this pointer is NULL_PTR, then the API will return E_NOT_OK.
Return Value Std_ReturnType E_OK, E_NOT_OK


This function enables or disables the internal loopback mode of SPI. Note: Only McSPI HW units supports this feature. This API should be called after Spi_Init is called. Otherwise this API will return E_NOT_OK. Also this API should not be called when the HW unit is busy. This API could be used to check the integrity of the SPI module. When the loopback mode is enabled, the data transferred is received back and hence the caller can verify and compare the TX buffer with RX buffer for any HW failures.

Description Comments
Service Name Spi_SetLoopbackMode Can potentially be turned OFF (Refer to Design Document provided in CSP)
Syntax uint32 Spi_SetLoopbackMode ( Spi_HWUnitType HWUnit, boolean LpbkEnable)
Service ID NA
Sync / Async ASync
Reentrancy Reentrant
Parameter in HWUnit SPI Hardware microcontroller peripheral unit ID. If this is invalid, then the API will return E_NOT_OK.
Parameters in LpbkEnable - Loopback enable/disable, TRUE - Enable loopback, FALSE - Disable loopback
Return Value Std_ReturnType E_OK : Loopback enable successfully E_NOT_OK : Loopback enable failed

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Interrupt Configuration

The Driver doesn’t register any interrupt service routine(ISR), it’s expected that consumer of this driver registers the required interrupt handler.

For every Spi instance an ISR needs to be registered. The Interrupt number associated with instance of the Spi is detailed in TRM. Please refer SpiApp_InterruptConfig () in Spi demo application.

Some of the spi interrupts are not routed/mapped to this core, these interrupts would require additional programming to route these to this core. Please refer SpiApp_InterruptConfig () in Spi demo application.

Dedicated interrupt lines are available from DMA after event completion to the R5 core (80-90 for MCU1_0) and (229 to 247 for MCU2_1).

Please refer mcusw\mcal_drv\mcal\examples_config\Spi_Demo_Cfg\output\generated\soc\j721e\mcu1_0\src\Spi_PBcfg.c for interrupt numbers.

Refer section (Spi Instance ID mapping and ISR mapping), for association between channel ID and ISR

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The driver doesn't configure the functional clock and power for the spi modules. It's expected that secondary boot loader(SBL) power-up the required modules. Please refer SBL documentation.

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Build and Running the Application

Please follow steps detailed in section (Build) to build library or example

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Steps to run example application

Please follow steps detailed in section (Build) to build example

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Memory Mapping

Various objects of this implementation (e.g. variables, functions, constants) are defined under different sections. The linker command file at (Examples Linker File (Select memory location to hold example binary)) defines separate section for these objects. When the driver is integrated, its expected that these sections are created and placed in appropriate memory locations. (Locations of these objects depend on the system design and performance needs)


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This driver implementation has been validated with cache enabled. For optimal performance it’s recommended to place (Memory Mapping) sections in cache enabled memory area.

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Dependencies on SW Modules


This implementation depends on the DET in order to report development errors and can be turned OFF. Refer section (Development Error Reporting) for detailed error codes.

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This implementation requires one level of exclusive access to guard critical sections. Invokes SchM_Enter_Spi_SPI_EXCLUSIVE_AREA_0 (), SchM_Exit_Spi_SPI_EXCLUSIVE_AREA_0 () to enter critical section and exit.

In the example implementation (File Structure SchM_Spi.c) , all the interrupts on CPU are disabled. However, disabling of the enabled Spi interrupt should suffice.

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File Structure

Detailed Directory Structure
  1. Driver implemented by : Spi.h, Spi_Irq.h, Spi.c, Spi_Priv.c,Spi_Mcspi.c Spi_Irq.c and Spi_Priv.h
  2. Example Configuration by : Spi_Cfg.h, Spi_Cfg.c,Spi_Lcfg.c and Spi_PBcfg.c
  3. Example Application by : McspiApp.c and McspiApp.h

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Error Handling

Development Error Reporting

Development errors are reported to the DET using the service Det_ReportError(), when enabled. The driver interface (Spi.h File Structure) lists the SID

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Error codes

Type of Error Related Error code Value (Hex)
Channel out of bounds, exceeds the maximum number of configured channels SPI_E_PARAM_CHANNEL 0x0A
Job out of bounds, exceeds the maximum number of configured jobs SPI_E_PARAM_JOB 0x0B
Sequence out of bounds, exceeds the maximum number of configured sequences SPI_E_PARAM_SEQ 0x0C
Length out of bounds, exceeds the maximum number of configured EB- or IB- buffer length SPI_E_PARAM_LENGTH 0x0D
The requested hardware unit does not exist SPI_E_PARAM_UNIT 0x0E
An invalid configuration has been passed (i.e. a NULL_PTR). This is an extension to AUTOSAR. SPI_E_PARAM_POINTER 0x10
A service was requested, but the driver has not been initialized SPI_E_UNINIT 0x1A
The requested sequence is still pending SPI_E_SEQ_PENDING 0x2A
Transmission of synchronous sequence in progress (not supported) SPI_E_SEQ_IN_PROCESS 0x3A
The driver is already initialized. SPI_E_ALREADY_INITIALIZED 0x4A

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Production Code Error Reporting

Production error are reported to DEM via the service DEM_ReportErrorStatus(). In addition to standard errors, this implementation reports "SPI_E_HARDWARE_ERROR" when SPI Timer register hardware reset fails.

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API Description

The AUTOSAR BSW Spi Driver specification details the APIs required for Spi Driver. Please refer to (Refer to Design Document provided in CSP) for detailed API description. Also refer to (Non Standard Service APIs) for non-standard APIs which are included in this implemented.

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Example Application

The example application demonstrate use of Spi module, the list below identifies key steps performed the example. The configuration file is present at (File Structure)

MCSPI example app is ported and tested with single MCSPI instance on MCU1_0 and MCU2_1 cores using UDMA MCU and MAIN NAVSS respectively. MCU MCSPI Instance on MCU1_0 core and MCSPI3 Instance on MCU2_1.

Please note that Multiple MCSPI Instances configuration is not tested.

Either interrupt/polling or DMA mode is supported per MCSPI instance for each configuration.Both modes are not supported simultaneously. Note: Spi_SetAsyncMode API should be bypassed in application is DMA mode if enabled.

  • Initializes “Result Status Flag”
  • SpiApp_Startup ()
    • Builds interrupt list and registers ISR for enabled Spi instances
    • Pinmux configuration required for internal loopback testing mode
  • SpiApp_PowerAndClkSrc ()
    • Dummy function for now.
  • Core application ()
    • For each enabled instance
      • Initialize Spi hardware
      • Enable loopback mode
      • Prints module version info
      • Set Async/Sync mode
      • Set Up and Initialize Tx and Rx Buffers
      • Start Sequence transmission
      • Wait for transmission completion
      • Get Sequence result
      • Compare Tx and Rx Buffers
      • De-Initialize Spi hardware
  • Checks for error status, stack corruption and prints result

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Example Log

    SPI_APP: Sample Application - STARTS !!!

    SPI MCAL Version Info
    Vendor ID           : 44
    Module ID           : 83
    SW Major Version    : 0
    SW Minor Version    : 1
    SW Patch Version    : 0

    SPI_APP: CH 1: JOBS 1: SEQ 1: HWUNIT 1: NUM OF WORDS 10000:!!!
    SPI_APP: Variant - Post Build being used !!!
    SPI_APP: SPI Async transmit in progress!!
    SPI_APP: SPI Stack Usage: 792 bytes
    SPI_APP: SPI Loopback Test Passed!!!

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Document Revision History

Revision Date Author Description Status
0.1 14 Oct 2018 Sunil M S First version Pending Review
0.2 22 Oct 2018 Sunil M S Addressed review comments Approved
0.3 16 Oct 2018 Sujith S Added Logs from J721E testing Approved
0.4 02 Nov 2020 Nikki S J7200 updated Approved
0.5 16 Mar 2021 Nikki S DMA Updates Approved
0.6 17 Mar 2022 Rohit T Removed J721E & J7200 specific contents Approved
0.7 08 Dec 2022 Subham Swain J721S2 updated Approved