TWI Scanner I2C address is 1 bit wrong

[StevenW807]

I'm using <TWI Scanner> example on nRF52 DK to find my sensor's address.

According to the sensor datasheet, the sensor's address is 0x21. However, <TWI Scanner> finds the address at 0x20. 

Any idea, please? 

[StevenW807]

Update. 

Now the PuTTY shows an unknown address. 

<info> app: TWI device detected at address 0x20.
<info> app: TWI device detected at address 0x22.

However, I only have 1 salve device, which is 0x22. 

Any idea why there is 0x20, please? 

[StevenW807]

According to the datasheet of my sensor, its I2C address should be 0x22. I only have 1 slave device. 

What I found is if I define the correct TWI address in <TWI sensor> code and run it, then <TWI scanner> could find 2 addresses. 
<info> app: TWI enabled
<info> app: TWI device detected at address 0x20.
<info> app: TWI device detected at address 0x22.

However, if I clean the solution, then run the <TWI scanner> again, it can only detect 0x20 address (no idea why I have this address). 

Note: my sensor requires a command (0x3608) to enter the continuous data reading mode. This command is unspecified in <TWI scanner> example. It's specified in <TWI sensor>. 

Question: 

1) Why I have a "ghost" address 0x20? 

2) Why I must run <TWI sensor> first, then run <TWI scanner>, then I can see 2 addresses (1 address is correct)? 

[Einar Thorsrud]

Hi,

I am not able to answer these questions at the moment, unfortunately. However I have ordered a SDP3x EK (EK-P4) so that I can test on my side. I t might take a couple of days before I get it, though. I will let you know when I have been able to test on my side.

[StevenW807]

Many appreciations, Einar! 

[StevenW807]

Hi, Einar. From Sensirion company official GitHub, it seems like they only support nRF51. 

I asked them that SDP3x will support nRF52 or not. And the reply email from Sensirion company says: 

No, we don’t support your specific microcontroller. I’m sorry but we don’t have the resources to customize drivers to every possible platform. We can only provide examples for some of the most common platforms.

Since I'm new to nRF52, does that mean it's impossible to get SDP31 measurements via nRF52 over TWI, pls?

What modifications should I make to let nRF52 get SDP31 measurements over TWI, pls? 

Thanks