What is the LL equivalent of HAL_I2C_Mem_Read?

[Loch]

Hi,

I found a tutorial for using a BME280 sensor with I2C in HAL (https://controllerstech.com/bme280-with-stm32/).

However, I need to use LL for it to fit into the rest of the program.

The main part I'm having an issue with is below as I can't find a command within LL that would easily replace it.

HAL_I2C_Mem_Read(BME280_I2C, BME280_ADDRESS, 0x88, 1, trimdata, 25, HAL_MAX_DELAY);

Any help or links to good I2C LL tutorials would be greatly apprecaited.

[Danish1]

One reason is that it doesn't map to a single LL call.

Take a look at the source-code for HAL_I2C_Mem_Read.

An I2C "memory-read" translates into an I2C write of the memory-location-to-read, followed by an I2C read of the data. And between them, in order to ensure that no other I2C controllers get a look-in and potentially change that memory-location-to-read, the I2C controller issues a "repeated-start" (i.e. i2c start without being preceded by an I2C stop).

Philips (now NXP) were the originators of the I2C protocol - see e.g. the Wikipedia entry for more information.

As to the LL commands, I've had a quick look and they seem to provide function-calls to access the stm32 peripheral registers for I2C. The registers are described in the Reference Manual, including sample code.

If you wish to go deeper than HAL I suggest you start with the section on I2C/SPI in the Reference Manual for your STM32.

Hope this helps,

Danish

[Loch]

Thanks for the other advice. I'll have to take a deeper look into how that function actually works.

If only there was a google translate for code.

[Imen.D]

Hello @Loch​ and welcome to the STM32 Community :)

You may start from the LL template project in the STM32CubeXX package and check the ready-to-use I2C example related to your device.

I advise you to look at the User Manual "Description of STM32XX HAL and low-layer drivers", it may help you to have more idea about the use of LL functions.

Check this FAQ, which describes few tips related to I2C peripheral on STM32 devices: STM32 I2C does not work, this may help you on your project.

When your question is answered, please close this topic by choosing Select as Best.

Imen

[Loch]

Ohh of course the example package. I knew I had seen something somewhere.

Thanks for the other advice too, I'll check it out