TCA9548A multi falsely detects several i2c devices per port

[hopfi]

Hey!

I am trying to get several MPU6050 IMUs to work on the TCA9548A multiplexer.

My current setup is to test with just one IMU, as in the following two pictures.

DSC01426.JPG (193.72 KiB) Viewed 876 times

DSC01427.JPG (204.24 KiB) Viewed 876 times

Now my problem is that when I run the scanner code from https://learn.adafruit.com/adafruit-tca ... g-and-test it tells me that there are several devices attached to each of the 8 channels. As you can see it detects the presence of my IMU with address 0x68 on port 0, but it also detects the addresses 0x0 and 0x60 on every port, although there is nothing else attached but my one IMU on port 0.

Code: Select all

TCAScanner ready!
TCA Port #0
Found I2C 0x0
Found I2C 0x60
Found I2C 0x68
TCA Port #1
Found I2C 0x0
Found I2C 0x60
TCA Port #2
Found I2C 0x0
Found I2C 0x60
TCA Port #3
Found I2C 0x0
Found I2C 0x60
TCA Port #4
Found I2C 0x0
Found I2C 0x60
TCA Port #5
Found I2C 0x0
Found I2C 0x60
TCA Port #6
Found I2C 0x0
Found I2C 0x60
TCA Port #7
Found I2C 0x0
Found I2C 0x60

It feels like I am missing something here. Any suggestions?

Thanks in advance for any feedback.

//Michael

[adafruit_support_mike]

Just to check, try disconnecting the IMU and see if you still get false positives on the other addresses.

[hopfi]

Yes, I disconnected the IMU (removed the sda and scl cables to it) and this is what I get:

Code: Select all

TCAScanner ready!
TCA Port #0
Found I2C 0x0
Found I2C 0x60
TCA Port #1
Found I2C 0x0
Found I2C 0x60
TCA Port #2
Found I2C 0x0
Found I2C 0x60
TCA Port #3
Found I2C 0x0
Found I2C 0x60
TCA Port #4
Found I2C 0x0
Found I2C 0x60
TCA Port #5
Found I2C 0x0
Found I2C 0x60
TCA Port #6
Found I2C 0x0
Found I2C 0x60
TCA Port #7
Found I2C 0x0
Found I2C 0x60

done

[hopfi]

I just noticed that it doesn't really affect what I am doing since I can simply run

Code: Select all

tcaselect(0)

and then in the code that connects to the IMU I can of course use the 0x68 address and it actually works.

Still I am bit curious as to why those "devices" appear there. Are 0x0 and 0x60 some special/reserved addresses that actually mean something?

Regards,
//Michael

[adafruit_support_mike]

There's nothing special about those addresses. The TCA9548's own I2C address should be 0x70.

It sounds like there's some kind of glitch in the chip. Let's get you another one.

Send a note containing a link to this thread and your order number to [email protected]. The folks there will get you a replacement.


(#2717)

[adafruit_support_bill]

In your first photo, it looks like you have a motor shield attached. The default address for the motor shield is 0x60, with an 'all-call' address of 0x70. And since it is directly connected to the Arduino, it will be detected regardless of the multiplexer channel selection.

[Freimund]

Obviously way late, but I'm having a similar issue using multiplexer and motor shield. Is there a way to work around the 'all-call'? I'm trying to get measurements from two VL53L0X connected through the multiplexer. I measure accurately seperately and can measure them correctly with the multiplexer and no motor shield, but not with everything together.

[adafruit_support_bill]

The All-Call address of the PCA9685 is fixed at 0x70. But the TCA9548 can be addressed anywhere from 0x70 to 0X77 using the address jumpers on the back of the board:

[Freimund]

And that solves the issue of having 0x0 and 0x60 active on every port?

[adafruit_support_bill]

Yes. You will be able to address the multiplexer separately from the motor shield.