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I2C V2 timings

Browse source code on GitHub

Overview

This sample simply demonstrate the get_config API of the stm32 I2C driver. The I2C peripheral configuration is checked regarding the I2C bitrate which can be:

• <I2C_BITRATE_FAST_STANDARD>

• <I2C_BITRATE_FAST>

• <I2C_BITRATE_FAST_PLUS>

In case of the I2C V2, the I2C peripheral of the STM32 microcontrollers have a TIMING register to write in order to generate the correct I2C clock signal. This value depends on the peripheral clock input and the I2C speed. The calculation of that TIMING value can be given by the STM32CubeMX application or by the present sample.

Because the code sequence to calculate the I2C V2 TIMING value is heavy, it is not advised to enable it in production binary. By enabling CONFIG_I2C_STM32_V2_TIMING flag, this sample allows to retrieve timing register configuration for the defined clock-frequency. User can then configure timing in his application by adapting the following dts snippet with the output of this sample:

&i2c {
    timings = <160000000 I2C_BITRATE_STANDARD  0xB0C03E40>,
                <160000000 I2C_BITRATE_FAST  0xC041090F>,
                <160000000 I2C_BITRATE_FAST_PLUS  0x6021050A>;
}

Building and Running

In order to run this sample, make sure to

• enable i2c node in your board DT file.

• enable the CONFIG_I2C_STM32_V2_TIMING=y in the board conf file

• alias the i2c-0 to your i2c node of the board overlay file

west build -b b_u585i_iot02a samples/boards/st/i2c_timing

Sample Output

When setting the b_u585i_iot02a.overlay to

/ {
    aliases {
     i2c-0 = &i2c2;
  };
};
&i2c2 {
    /delete-property/ clock-frequency;
    clock-frequency = <I2C_BITRATE_FAST>;
};

The sample gives the corresponding TIMING value to report to the Device Tree:

I2C timing value, report to the DTS :
timings = <160000000 I2C_BITRATE_FAST  0xC041090F>;

I2C config : I2C_BITRATE_FAST

See also

I2C Interface