BMP280 Undetectable on Nano until BMP280 ran on UNO

Hardware Nano Family Classic Nano
1

I completed my weather station project(just a simple DHT11) through the UNO and wanted to move it to something with a smaller footprint.

Purchased the Elegoo brand of Nano with the CH340 chip on the ATmega328P board. In IDE, I selected the new board(port auto-connected, but I had to choose Nano manually). Then, I uploaded the sketch, and it worked flawlessly.

I received my BMP280s(confirmed by getting out the magnifying glass...made me feel old) and plugged it into the I2C configuration. Nothing when I ran the Adafruit BMP280 sketch.

I tried to run the I2C sketch to determine if it was 0x76 or 0x77. Out of frustration, I went back to the UNO, hooked everything up, and had zero issues. It was detected immediately and working. I moved the BMP280 to the Nano, which was finally detectable and working after hooking the same sensor up to the UNO.

I have a few breadboards and jumper wires. All the cables stayed the same. The only thing that changed was I physically moved the sensor from the UNO to Nano. I checked the soldering, and all joints were good and had good continuity.

Was this just a weird coincidence that the UNO "woke" up the BMP280 to where the Nano CH340 could detect said sensor?

2

My bet is on a bad connection. Or maybe a swap of SDA and SCL.

3

Wiring was solid and not touched. Visually and continuity checked. Even did it on a 2nd board.

Did this on both sensors I checked. I guess I could record the other 3 to see if it can be reproduced.

4

The form factor and pinouts of Uno and Nano are different, you could not replace the Uno with Nano without changing the wiring. (An Uno will not even plug into a Breadboard.) When you did that, you fixed whatever mistake you made before.

There is no memory on the BMP280 sensor which could remember that it had been "activated" by the Uno and subsequently cause it to work on a Nano.

5

Breadboard A(Nano) wiring done. Sensor did not work.

Wired Breadboard B for the Uno to check the sensor. You can very well use a breadboard with an Uno. Doesn't have to plug into the breadboard to utilize it.

Plugged sensor into Breadboard B and the I2C scan found it.

Unplugged sensor from Breadboard B back to A without touching the wiring.

Sensor now works on both Uno and Nano without any wiring changed.

Hope that makes it clear.

6

Even when not touching the wires in the breadboards, the breadboard setups are always my #1 reason for weird problems. Especially the cheap Ebay/Ali ones that seem to oxidize like a vintage Alfa Romeo.

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