Arduino Nano 33 IOT Power supply

Official Hardware Nano Family Nano 33 IoT
1

Dear all,
Apparently I ran into an 3.3V power issue when powering the Nano via USB and use the Serial.printLn() function for debug output.

I developed the Sketch for a Arduino UNO wifi rev 2, it works well on that device but I needed more resources and switched to the Nano 33 IOT what works quite well beside this issue here.

I connected a sensor via I2C but see that the 3.3 V power supply shows a lot of noise... but only if I have the „serial monitor“ window of the IDE open. Without that, the 3.3V power appears to be much mor stable...

So the setup is:

  • Arduino Nano 33 IOT +seeed nano base shield with grove connector for I2C + Seeed RGB Sensor with I2C interface and (Short) cable

  • Sketch is quite large, used WIFI and a sensor connected via I2C.

  • WIFI is constantly connected.

  • Sensor is read every second.

  • Some processing of data is going on.

  • No specific power saving mechanisms implemented.

  • connected and powered via USB (USB Hub with separate power supply, tested also directly with PC)

  • IDE is 1.8.13

Test... Protocol...:

  • no Changes done to use the Sketch crated for an UNO WiFi rev2 on a Nano 33 IOT

  • Sketch is compiled and loaded to the Nano

  • „serial monitor“ window of IDE is closed

  • reset Nano

  • => 3.3V Power seems to be OK

  • => Nano works as expected (SKetch running, WIFI connection established, no Idea if the sensor read works)

  • open „serial monitor“ window in IDE

  • => 3.3V Power becomes extremely noisy

  • => WiFi and Sketch still running

  • => „serial monitor“ window in IDE showing serial debug output and shows that the sensor read does not work, probably due to 3.3V VCC noise measured on the Sensor.

  • close „serial monitor“ window in IDE

  • => 3.3V Power is still extremely noisy

  • reset Nano

  • => 3.3V Power seems to be OK

  • => Nano works as expected (SKetch running, WIFI connection established, no Idea if the sensor read works)

Question:
Anny Suggestions what might be the cause of this and/or how to fix it?

2

Please be aware that there are different NANO's and that some of the earlier and older NANO shields may not be fully compatible.

The newer NAO's have thier own sections lower down the section page if you need the post to be moved.
Use REPORT TO MODERATOR for that to be done for you.

3

Thanks for the hint, I will request to move this thread(?) to the nano 33 IOT forum and rename it so it includes the "seeed shield" term so that others with the same issue can find it easely...

First (in the hope that this response will be moved as well) some more information:

I solved the issue, it is, in fact, related to the shield.

The 8 grove connectors on that shield all provide a signal called VCC, but that signal is NOT connected to the NANO VCC but to the VUSB output of the nano 33 IOT... what is open by default (you have to solder a bridge on the NANO 33 side to provide the 5V from the USB Port directly there)

So in my setup the sensor had no "official" power supply at all but was still able to do "something" (e.g. become initialized), probably by the I2C IO lines via backfeeding... (modern times, circuits almost don't need any power anymore :-))

4

Your post, and perhaps a few others, prompted me to add a 0.1uf decoupling capacitor to my A0 sensor. This cleaned the instability I was getting. My project is working reliably now, so I’m planning to repackage it all to eliminate the jumper wires and keep my capacitor close to ground. Good luck!