STM32F0xx_HAL_I2c.c: I2C_RequestMemoryRead not interrupt based

VLock.1 · ‎2020-10-20

Hello,

I am currently using a STM32F030CCT6 with the STM32F0xx_HAL_DRIVER generated by CubeMx. The version of the driver/cube is STM32Cube_FW_F0_V1.10.0.

In my program, I have a low priority task that calls HAL_I2C_Mem_Read_IT. This function is interrupt based and therefore I should have no problem completing the I2C request. However, once in a while I get a timeout. I investigated that timeout and found out that my task get switch during the call to HAL_I2C_Mem_Read_IT.

Going into HAL_I2C_Mem_Read_IT, I see that this function is called I2C_RequestMemoryRead. This function is responsible to send the device address and the memory address. When looking into the implementation I found that this function is not interrupt based!

I get a timeout when the task switch during I2C_RequestMemoryRead!

I was wondering if there was a particular reason why the function I2C_RequestMemoryRead is not interrupt based? Is this wanted? Is there a driver that implements I2C_RequestMemoryRead with interrupts?

Thank you!

TDK · ‎2020-10-20

HAL support for I2C in interrupt mode just isn't well implemented. Probably partly because the I2C peripheral and protocol is relatively complicated compared to UART/SPI.

The F4 library seems to not have this drawback at a glance. You could try porting:

https://github.com/STMicroelectronics/STM32CubeF4/blob/9f5ea7421d22c724516d00218b350d1e09a54a2c/Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_i2c.c#L2873

In the CubeF4 repo, HAL_I2C_Mem_Read_DMA seems to rely on I2C_RequestMemoryRead, but HAL_I2C_Mem_Read_IT does not.

No idea how common those two peripherals are.

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VLock.1 · ‎2020-10-21

Thank you for the quick answer!

I added a critical section for the call to "HAL_I2C_Mem_Read_IT" to prevent task switching it did the job. Would of like a cleaner solution but I am not willing at this moment to modify the hal driver to have everything in interrupts.

However, the point that you bring is a good one and anyone could try and implement the F4 driver into the F1. The driver is quite different. I can see the the "I2C_HandleTypeDef *hi2c" as new members suchs as: "Devaddress", "Memaddress","MemaddSize". But I am guessing that the architecture could be reproduce into the F0 and make " HAL_I2C_Mem_Read_IT" completely in interrupt.

In the mean time, I also notice that the function "HAL_I2C_IsDeviceReady" is not interrupt based. It is not declared at so, but if you want to have everything in interrupt this function should probably also be modified.