NAU7802 issue over SparkFun QwiicBus Kit

Sensors Force & Weight
1

Hi SparkFun support team,

I have cabled this configuration:

SparkFun IoT RedBoard ESP32 Development Board - Qwiic cable - MidPoint - Eth cable CAT 6 - EndPoint - Qwiic cable - SparkFun Qwiic Scale NAU7802 one side and SparkFun Environmental Sensor BME688 (Qwiic) on the other side.

The BME688 works perfectly but not the NAU7802 scale.

The scale is not visible at I2C level (not show I2C address).

If I connect the NAU7802 scale on the board or on MidPoint, the scale works perfectly.

So there is something on MidPoint-End point that cause this issue.

This is reproducible all the time.

What I need to do for use the NAU7802 over the MidPoint-End kit ?

Many Thanks and Best Regards.

Ivan

My next step is check with oscilloscope.

2

I’d guess the i2c pull-up resistance is too high; https://learn.sparkfun.com/tutorials/qw … e-assembly scroll up to the paragraph above and see the location of the jumper pads…cut between those and re-try (first try NAU by itself @ endpoint after i2c jumpers cut) - does it appear on i2c? If so, add the BME back (and if either disappears, you may need to disable the BME i2c pull ups as well)

3

Hi TS-Russell,

many thanks for your quick reply.

Your advice is correct.

After removing the pull-up (2 z 2.2kΩ) , I was able to scan the address and use it without any problem.

As additional test I have added Qwiic Mux PCA9846 for solve the static I2C address of NAU7802, and it doesn’t show for the same pull up issue :wink:

After removing the pull-up (2 z 2.2kΩ) on Qwiic Mux PCA9846 everything works like a charm.

Everything is working as expected.

Ivan