Last edited 11 months ago

SPI internal peripheral

Applicable for STM32MP13x lines, STM32MP15x lines

1. Article purpose[edit source]

The purpose of this article is to:

  • briefly introduce the SPI peripheral and its main features,
  • indicate the peripheral instances assignment at boot time and their assignment at runtime (including whether instances can be allocated to secure contexts),
  • list the software frameworks and drivers managing the peripheral,
  • explain how to configure the peripheral.

2. Peripheral overview[edit source]

The SPI peripheral is used to communicate with an external devices using the SPI (Serial Peripheral Interface).
A subset of the SPI instances supports the I2S audio protocol. These SPI/I2S peripherals can alternatively be used in audio applications, when they are configured as an I2S interface. Refer to peripheral runtime assignment chapter to check I2S feature support for each SPI instance.

2.1. SPI main features[edit source]

  • Full-duplex, half-duplex and simplex synchronous modes.
  • Slave and master modes.

2.2. I2S main features[edit source]

Only available for SPI supporting I2S mode.

  • Full-duplex or simplex modes.
  • Slave and master modes.
  • Four audio protocols supported.

2.3. Specific features[edit source]

Some of the SPI peripheral characteristics depend on I2S support, as summarized in following table:

SPI modes/features I2S supported I2S not supported
Rx & TxFIFO size (N) [x 8-bit] 16 8
Maximum configurable data size [bits] 32 16

Refer to the STM32 MPU reference manuals for the complete list of features, and to the software frameworks and drivers, introduced below, to see which features are implemented.

3. Peripheral usage[edit source]

This chapter is applicable in the scope of the OpenSTLinux BSP running on the Arm® Cortex®-A processor(s), and the STM32CubeMPU Package running on the Arm® Cortex®-M processor.

3.1. Boot time assignment[edit source]

The SPI peripheral is not used at boot time.

3.2. Runtime assignment[edit source]

3.2.1. On STM32MP13x lines More info.png[edit source]

Click on the right to expand the legend...

STM32MP13 internal peripherals

Check boxes illustrate the possible peripheral allocations supported by STM32 MPU Embedded Software:

  • means that the peripheral can be assigned to the given runtime context.
  • means that the peripheral is assigned by default to the given runtime context and that the peripheral is mandatory for the STM32 MPU Embedded Software distribution.
  • means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in STM32 MPU Embedded Software distribution.
  • is used for system peripherals that cannot be unchecked because they are hardware connected in the device.

Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32MP13 reference manuals.

Domain Peripheral Runtime allocation Comment
Instance Cortex-A7
secure
(OP-TEE)
Cortex-A7
non-secure
(Linux)
Low speed interface
or
audio
SPI SPI2S1
SPI2S2
SPI2S3
SPI2S4 Assignment (single choice)
SPI5 Assignment (single choice)

3.2.2. On STM32MP15x lines More info.png[edit source]

Click on the right to expand the legend...

STM32MP15 internal peripherals

Check boxes illustrate the possible peripheral allocations supported by STM32 MPU Embedded Software:

  • means that the peripheral can be assigned to the given runtime context.
  • means that the peripheral is assigned by default to the given runtime context and that the peripheral is mandatory for the STM32 MPU Embedded Software distribution.
  • means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in STM32 MPU Embedded Software distribution.
  • is used for system peripherals that cannot be unchecked because they are hardware connected in the device.

Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possiblities might be described in STM32MP15 reference manuals.

Domain Peripheral Runtime allocation Comment
Instance Cortex-A7
secure
(OP-TEE)
Cortex-A7
non-secure
(Linux)
Cortex-M4

(STM32Cube)
Low speed interface
or
audio
SPI SPI2S1 Assignment (single choice)
SPI2S2 Assignment (single choice)
SPI2S3 Assignment (single choice)
SPI4 Assignment (single choice)
SPI5 Assignment (single choice)
SPI6 Assignment (single choice)

4. Software frameworks and drivers[edit source]

Below are listed the software frameworks and drivers managing the SPI peripheral for the embedded software components listed in the above tables.

5. How to assign and configure the peripheral[edit source]

The peripheral assignment can be done via the STM32CubeMX graphical tool (and manually completed if needed).
This tool also helps to configure the peripheral:

  • partial device trees (pin control and clock tree) generation for the OpenSTLinux software components,
  • HAL initialization code generation for the STM32CubeMPU Package.

The configuration is applied by the firmware running in the context in which the peripheral is assigned.

When the Arm® Cortex®-A7 core operates in non-secure access mode, the SPI is controlled by the Linux kernel framework.

  • SPI mode:

Refer to SPI framework to check how to drive SPI through Linux kernel.

  • I2S mode:

Refer to I2S Linux driver to drive the SPI through Linux kernel ALSA framework. Refer to Soundcard configuration to configure it through the Linux kernel device tree[1].

6. References[edit source]