2 dud Nanos, brand new

both nanos hook up to the IOT editor and, after programming, respond to Alexa commands (I can see the appropriate responses in the serial monitor). However, neither of them has any output voltage on the 5v pin (300 mv noise) and their Tx pins are inoperative. My application does not use any other pins except the USB port, so I haven’t checked whether the I/O pins are active.

The parts that are working work fine on USB power and with 8.5v applied to the Vin pin. But still no voltage on the 5v pin.

Am I missing some magic fuse to get the I/Os, specifically Tx, working?

Hello Dr_Quack,

I am not sure about why the TX isn't working, I am guessing that is more code related. As far as I know, the TX1/RX0 pins run off of Serial1 not Serial. However, and just to double-check, if you want 5V out of the pin between RST and A7 you can only power the board through the USB and you have to solder between the two pads directly above the pin. If you power the board through the VIN pin it doesn't output the 5V.

Here is the extract from one of the IOT pages:

5V on that pin is available only when two conditions are met: you make a solder bridge on the two pads marked as VUSB and you power the NANO 33 IoT through the USB port. If you power the board from the VIN pin, you won’t get any regulated 5V and therefore even if you do the solder bridge, nothing will come out of that 5V pin. The 3.3V, on the other hand, is always available and supports enough current to drive your sensors. Please make your designs so that sensors and actuators are driven with 3.3V and work with 3.3V digital IO levels. 5V is now an option for many modules and 3.3V is becoming the standard voltage for electronic ICs.

I have attached an image that I pinched from this post.

Sorry if that is a bit of a surficial answer. Hope it helps!


It's Quark, not Quack! :slight_smile:

Thanks for the info on the 5v. I'll see if I can find info on how Tx works. I assumed that it was like my previous Nanos. I thought that numbered serial ports were only on the Megas.

Sorry about the name!

Yes, there is definitely a move to 3.3V at the moment which is great but also a bit problematic, you have to be super careful not to send any 5V signals, even to the analog pins.

The page I link states the follow on the serial if it helps:

Serial ports on the Arduino NANO 33 IoT
The USB connector of the board is directly connected to the USB host pins of the SAMD21. This routing enables you to use the Arduino NANO 33 IoT as a client USB peripheral (acting as a mouse or a keyboard connected to the computer) or as a USB host device so that devices like a mouse, keyboard, or an Android phone can be connected to the Arduino NANO 33 IoT. This port can also be used as a virtual serial port using the Serial object in the Arduino programming language. The RX0 and TX1 pins are a second serial port available as Serial1.

You are correct! Here's from https://www.arduino.cc/en/Guide/NANO33IoT:

...The RX0 and TX1 pins are a second serial port available as Serial1....

It appears that "serial" points to the UART/USB connector (I do see the serial signal that I expected on the USB connection).

Thanks again.