Hi everyone,
I am trying to find a way to use the nano 33 BLE with an external (not the on-board micro usb receptacle) usb input.
Currently I am thinking of two possible ways I could achieve this:
- I could connect VBUS from my external usb input to the 5V pin of the nano 33 BLE and short out SJ1 (see SJ1 in section C5 of the official arduino nano 33 BLE schematic and the green box in the picture below).
Now I see that D- and D+ are directly connected to NINA-B3X section B3 of the same schematic. I see this notice posted everywhere: Please note: Arduino Nano 33 BLE only supports 3.3V I/Os and is NOT 5V tolerant so please make sure you are not directly connecting 5V signals to this board or it will be damaged. Also, as opposed to Arduino Nano boards that support 5V operation, the 5V pin does NOT supply voltage but is rather connected, through a jumper, to the USB power input.
This notice however leaves me wondering if I can connect D- D+ directly to pin 54 and 55 of the NINA-B3X chip as well? This trace is not well accessible but being familiar with the previous arduino nano I know there were D- and D+ pads on the back (I never knew what they are and what they are meant to be used for so If someone here knows please share!) that I could connect them to I am guessing that these are the pads in the red square in the picture below. Connect GND to the ground pins of the nano and that should be it right?
- Another way would be to use a USB UART IC for example the FT232RL chip and connect the USB D- and D+ to the FT232RL and from there connect the FT232RL to the nano via the Rx and Tx pins however this results in the same question as above can the Tx and Rx pins of the Nano 33 BLE handle this? The FT232RL has a 3.3V low dropout regulator built in but I don't think this is a good idea to use because of the maximum rated 50mA (datasheet bottom of page 7) which can be drawn from this pin.
I would like to eventually solder the nano to a custom pcb with its castellations. Making solder connections on the bottom of the nano are not ideal in this case as they would elevate the nano. Maybe a large cutout on the pcb at the place of the the solder joint would do the trick and prevent the board from being elevated?
I'd love to hear your suggestions
Alex