TCA9548A I2C multiplexer with Ni-8452

[soumik.1506]

Hi there, I have a number of SHT85 sensors with me. I am able to get the humidity and temperature data from one sensor using the NI - 8452 I2C interface. Each sensor has 0x44 as the I2C address and it requires 2 other I2C commands to get the data from it. I have activated the internal pull-ups at the logical voltage of 3.3V.

Now i want to setup at least 2 SHT85 sensors with the I2C interface in the NI-8452. Since all the sensors have the same address, i want to use the TCA9548A I2C multiplexer on the single I2C bus in the interface, so that i get the humidity and temperature data from both the sensors. This multiplexer has an address of 0x70 and 8 channels (0 - 7). 

To start with i have just connected only one SHT85 sensor at channel 0. I have simply changed the address in the I2C configuration and added 2 extra I2C wirte blocks with idea of selecting the I2C multiplexer channel which had the sensor connected. I have retained the I2C write block which calls the SHT sensor (with address 0x44) follwoed by the other I2C commands to get the data from it. 

On execution, there were no errors flagged while the program was running but i was not getting any data from the sensor via the multiplexer. Please find the attached VI and please point out what am i missing.

[crossrulz]

Your main problem seems to be that you are not understanding that the Address property sets the address that the NI-8452 will attempt to communicate with when an interaction is done. You need to actively set that property when you want to change which I2C device you want to talk with.

[soumik.1506]

Thanks for the pointer, I will try this changes suggested.

Correct me if i have got this wrong - by following the method you have suggested, i simply need to change the data meant for selecting the channel at 0x70. And after that it is simply commanding the SHT85 sensor connected at that channel. 

[crossrulz]

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@soumik.1506 wrote:

Correct me if i have got this wrong - by following the method you have suggested, i simply need to change the data meant for selecting the channel at 0x70. And after that it is simply commanding the SHT85 sensor connected at that channel. 

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That is correct.