I2C indexing issue

[lbos_7]

I'm using a Raspberry Pi 4 model B with a 16 channel relay board (address: 0x20), an adafruit mcp 4725 digital to analog converter (address: 0x63), 2 adafruit ads 1115 (addresses: 0x48, 0x4b), and 7 adafruit mcp 9601 thermocouple amplifiers (addresses: 0x60, 0x61, 0x62, 0x64, 0x65, 0x66, 0x67) and I'm having an issues detecting all of the devices consistently when I run the sudo i2cdetect -y -r 1 command in the terminal window. Sometimes the 0x65, 0x66, and 0x67 addresses never show up, sometimes some of them do, and sometimes all of them show up with no issue. I also can disconnect other pieces of hardware and the addresses that I'm missing will show up. I suspect this may have something to do with all of the sets of pullup resistors, but I'm not sure where the pull up resistors are on the hardware I have, how to disconnect them, or if it's even possible to disconnect them.

[lbos_7]

Here is a picture of the terminal and the issue that keeps occurring

[lbos_7]

and here is the link to another forum post relating to the pullup resistors with i2c viewtopic.php?p=866848&hilit=remove+pullups#p866848

[adafruit_support_mike]

Check the resistance between the RasPi's 3.3V pin and the SDA/SCL pins.

According to the I2C spec, the pull-ups should draw about 1mA when either SDA or SCL is pulled low. For a 3.3V supply, that puts the expected pull-up resistance around 3.3k.

I2C works far outside that estimate, but given the number of items you've connected, there's a small chance that the combined pull-up resistances are too strong for the RasPi's I2C pins. I'd only expect that to be a problem if the combined pull-up resistance is less than about 1k though.

[lbos_7]

Thanks for your response. One thing I realized I forgot to mention is that I'm using a HAT for the Pi that is a 3.3V to 5V converter. Does that affect the recommended procedure that you gave me?

[lbos_7]

I just checked the resistances and I got around 1.3 kOhm for both.

[adafruit_support_mike]

Thanks for your response. One thing I realized I forgot to mention is that I'm using a HAT for the Pi that is a 3.3V to 5V converter. Does that affect the recommended procedure that you gave me?

No. The RasPi's SDA and SCL pins operate at 3.3V, and that's all that matters.

I just checked the resistances and I got around 1.3 kOhm for both.

That's a little low, but still a reasonable value. It puts the pull-down current at 2.5mA, which a RasPi pin can handle.

Let's take a look at the hardware. Post a photo showing your hardware and connections and we'll take a look. 800x600 images usually work best.

[lbos_7]

Thanks for your help. The issue has been resolved.