I2C Four-Wire Scheme

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I2C Four-Wire Scheme

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ASN7
Contributor II

I'm working with a S32K314 on a custom board and have connected a temperature sensor to the SDAS and SCLS lines for I2C communication. This sensor is the only I2C device, and it isn’t connected to any other I2C lines. I wish to use LPSPI. 

From my understanding of the manual (image below), it appears that SDAS and SCLS are secondary lines. Could someone confirm if these lines are suitable for a Two-Wire I2C scheme with my temperature sensor, or if I should be using the primary SDA and SCL lines instead?

Thanks in advance for any clarification!

ASN7_0-1730189638617.png

 

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Julián_AragónM
NXP TechSupport
NXP TechSupport

Hi @ASN7,

The four-wire scheme, instead of using traditional I2C SDA\SCL bidirectional lines, it adds an option to split them into input and output functionality. This in order to improve the noise immunity of the I2C bus.

This change can be implemented with two transistors, six resistors, and two diodes. You can see a recommended connection diagram in the same chapter: 

Julin_AragnM_0-1730227650471.png

This implementation choice is dependent on your application. You must weigh the benefit of the robustness against the additional system BOM costs. 

If this is not critical or safety implementation, the traditional two-wire configuration should be enough for most sensors.

Best regards,
Julián

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ASN7
Contributor II

So to conclude your answer, it would not be possible to only use SDAS and SCLS pins. I would have to connect SDA and SCL as well in order to use SDAS and SCLS. 

I hope my understanding is correct. Thank you. 

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Julián_AragónM
NXP TechSupport
NXP TechSupport

Hi @ASN7,

Yes, that is correct.

Best regards,
Julián

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Julián_AragónM
NXP TechSupport
NXP TechSupport

Hi @ASN7,

The four-wire scheme, instead of using traditional I2C SDA\SCL bidirectional lines, it adds an option to split them into input and output functionality. This in order to improve the noise immunity of the I2C bus.

This change can be implemented with two transistors, six resistors, and two diodes. You can see a recommended connection diagram in the same chapter: 

Julin_AragnM_0-1730227650471.png

This implementation choice is dependent on your application. You must weigh the benefit of the robustness against the additional system BOM costs. 

If this is not critical or safety implementation, the traditional two-wire configuration should be enough for most sensors.

Best regards,
Julián

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