SPI Communication between mcu and mpu in linux

[Nesnes]

We have a custom board with both an MCU and an MPU that communicate via SPI. The MCU controls various IOs on the board, and we want to configure and monitor these IOs through our Linux-based MPU. Are there any recommended protocols or example applications for this kind of communication over SPI?

Additionally, what would be the best approach or protocol to use for efficiently configuring and monitoring IOs in such a setup?

[ToradexAI]

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The context provided does not include specific protocols or example applications for SPI communication between an MCU and an MPU in a Linux environment. However, I can offer some general guidance based on typical practices:

1. Protocol Selection: For communication between an MCU and an MPU over SPI, you might consider using a simple custom protocol or a lightweight protocol like Modbus SPI, which is often used for industrial communication. The choice of protocol will depend on the complexity of the data you need to exchange and the capabilities of your devices.

2. User-Space Access: You can use the spidev interface in Linux to access SPI devices from user space. This allows you to write applications in C or other languages to send and receive data over SPI. The spidev_test.c sample code in the Linux kernel sources can serve as a starting point for developing your application.

3. Kernel-Space Drivers: If you need more control or performance, consider writing a kernel-space driver. The Linux kernel provides drivers for various SPI devices, and you can use these as examples. For instance, the MCP2515 CAN controller driver is mentioned in the context as an example of an SPI device driver.

4. Efficient Configuration and Monitoring: To efficiently configure and monitor IOs, ensure that your protocol includes commands for reading and writing the necessary registers on the MCU. You might also implement a mechanism for asynchronous notifications from the MCU to the MPU for real-time monitoring.

5. Container Access: If you are using Torizon, you can expose SPI devices to containers using the --device flag in Docker, allowing your containerized applications to access the SPI bus.

For more specific guidance, you would need to refer to the datasheets of your MCU and MPU, as well as any existing documentation on the protocols they support.

Please, also check if these links can help you solve your problem:

SPI (Linux) | Toradex Developer Center

SPI Comm between A Core or M Core

Hello, On our board, we have an additional MCU dedicated to managing I/O and sensor measurements and controls. We need to display and configure these I/Os on the Linux side. We are considering using SPI to facilitate communication between the extra MCU and the i.MX8MP MPU. Should we connect the SPI directly to the A core, or would it be better to use the M core and leverage rpmsg APIs? We are aiming for low latency in our system while ensuring that no data from the MCU is missed. Which approa…

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[lucas_az.tx]

Hi @Nesnes !

What is the Computer on Module (CoM) that you are using?

Just to clarify, when you say that you want to use MPU to monitor these IOs do you mean to check if everything is working properly? Or do you want the MPU to configure and monitor the MCU itself?

Please, give me more details about how the project will work (both hardware and software).

Best regards.
Lucas Azeituno

[Nesnes]

Hi @lucas_az.tx

Our project is an HMI, we’re using mcu for IO control purposes and communication needed to monitor those IO states via display which is controlled by the MPU.

Best regards.

[lucas_az.tx]

Hi @Nesnes !

Can you specify which Toradex Computer on Module (CoM) you are using?

You can use tdx-info command to get info about the hardware and software.

Best regards.
Lucas Azeituno