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Interfacing (DSI, CSI, I2C, etc.) • Re: I2C Bus 1 Not Responding

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is there a hardware problem?
Yes.
Most likely something will be pulling SCL low and therefore the I2C controller thinks the bus is busy or clock stretching and times out. Check your wiring carefully.
If using Raspberry Pi OS you could also use "pinctrl get 2,3" to observe the actual state of the GPIO lines that i2c-1 are exposed through. I don't know whether Ubuntu provides that utility (https://github.com/raspberrypi/utils/tr ... er/pinctrl)
Thanks. I just tried this (ADS1115 on a blank breadboard, tried it at 3V3 then 5V, same result), and here's the output:

Code:

 2: a3    pu | hi // GPIO2 = SDA1 3: a3    pu | hi // GPIO3 = SCL1
Here's the output without either SDA/SCL plugged in:

Code:

 2: a3    pu | hi // GPIO2 = SDA1 3: a3    pu | hi // GPIO3 = SCL1
I see that a3 means it's set to an alt mode, but I don't know what else to make of this. Is this normal output otherwise?

Statistics: Posted by siyengar — Thu Feb 12, 2026 7:49 am



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