Which I2C bus is exposed on Nordic Thingy 52 for custom application development?

[Kartik]

Hello fellow Nordic-ians,

I see that on the Nordic Thingy 52 I2C bus interface (SCL and SDA) is provided at 3 different ports i.e. P4, P5 and P7.

From other related documentation I understand that this is the external I2C bus provided for custom application development. This is not the same I2C bus which interfaces the environment sensors on Thingy. Is my understanding correct? 

If so, then does it mean that custom applications should only interface additional I2C devices only using the external I2C bus?

As I get it, the external I2C bus pins are SCL is 15 and SDA is 14. Please correct me if this is not correct.

[awneil]

Have you looked at the schematics - surely that would answer this question ?

[Kartik]

From the schematics my interpretation is that the SCL - SDA exposed on Nordic Thingy device is the external I2C bus.

It is not the same I2C bus on which the on-chip environmental and UI sensors are interfaced.

My requirement is to interface the MAX30105 heart rate and pulse oximetry sensor with the Nordic thingy while retaining its original application.

I thought it would have been simple to interface this external sensor to same I2C bus which interfaces the environmental and UI sensors; but it seems not possible due to hardware. So I am now trying to use SCL-SDA exposed on the Thingy, which I am assuming to be the external I2C bus (pin 14 and 15).

[ovrebekk]

Hi Kartik

You are correct, the SCL/SDA lines exposed on P4, P5 and P7 belong to the external I2C bus, which is only used by the low power accelerometer out of the box and can be extended to use your own sensors. 

For an overview of this refer to the pin maps and connectors section of the Nordic Thingy documentation on the infocenter. 

Best regards
Torbjørn