RaspPi HAT multiplexer with I2C sensors with same address

Qwiic System
1

I am trying to use the SparkFun Qwiic HAT for Raspberry Pi (DEV-14459) with several sensors attached. The challenge I am having is that the temperature sensors have the same I2C address (0x77). Using i2cdetect will show two of the addresses 0x69 (9DoF IMU - icm20948) and 0x77 (one of the temperature sensors); however, I have both temperature sensors connected at the same time. I have checked plugging each temperature sensor in individually to see them appear as 0x77.

Is there a way to indicated which of the four I2C ports to read from? For example, could I toggle between ports 2 and 3 even though the sensors have the same I2C address?

I am using the Blue Robotics I2C temperature sensors:

https://bluerobotics.com/store/sensors- … sensor-r1/

The documentation for the temperature sensors shows that the default address is 0x77. Looking further into the sensor documentation, the address can be either 0x76 or 0x77, but there is a pull-down 10K resistor that defaults the address to 0x77. Unfortunately, the sensor is potted so I only have access to the 4 wires that go to the Qwiic connect (VDC, GND, SCL, SDA).

See https://github.com/bluerobotics/Celsius … ematic.pdf

…and…

https://www.te.com/commerce/DocumentDel … G-NICO-018

Thanks in advance for any assistance!

2

The address have to be different. Is it really not possible to change the address on the sensor?

3

Unfortunately not an easy way that potentially wouldn’t ruin the sensor. The company added a 10K pull-down resistor to the pin that is used to change the address to 0x76, so as far as I can tell, all of these temp sensors can only be 0x77 (perhaps because they sell another product that defaults to 0x76.). I would have to cut back the waterproofing material to solder a bridge together to pull the pin high. As far as I have read on their forum, there isn’t a way to change the address over the SCL/SDA pins.

4

Hi cshill.

The Qwiic Hat doesn’t have a MUX in it at all, all 4 ports are wired together and are considered one port.

Are you using an external MUX like the [Qwiic Mux along with your sensors?](https://www.sparkfun.com/products/14685)

5

I’ll give that a shot. I do have one of those on hand but don’t have it integrated at the moment. Hopefully that solves the problem. Thanks!