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Topic: Powering and programming the Nano 33 BLE through an external FT232RL chip (Read 130 times) previous topic - next topic

TheAliw1

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

gbafamily

If the goal is to extend the Nano micro USB port to a connector on the enclosure, take a look at this panel mount micro USB extender.

https://www.adafruit.com/product/4213

TheAliw1

Thanks gbafamilty for your reply,

In my application I am however not only trying to extend the Micro USB port. In my project I am making an Arduino shield that adds some sensors the values of which I send over bluetooth to another Arduino. The Arduino will be ran off of a couple 18650 Li-ion batteries. I want the package to be as small as possible. Let's however not go into discussion about the batteries.

After looking at the schematic for over a week now I conclude myself that D+ and D- of the USB interface on pin 54 and 55 of the NINA-B3X have to be 5V tolerant. There is nothing between them on the schematic. So I will be connecting my USB Vbus to the Vbus pin next to the reset pin and close the solder joint SJ1 (red box of my previous post). GND to one of the ground pins. For D+ and D- I could use the small pads. However I think adding another USB to serial interface and connect them to the external TX and RX pins of the Arduino will be more convenient.

The questions remains: is TX and RX 5V tolerant? Pins 37 and 38 of the NINA-B3X

david_2018

If your intent is to be able to upload sketches to the board, then connecting an external USB to serial interface to the RX and TX pins probably will not work without modifications to the bootloader, because it is expected that the internal USB interface will be used for that.  The D+ and D- points are tolerant of the voltages on a USB port, since they are connected directly to the USB port on the board, and to the built-in USB port of the NINA-B3X.  RX and TX would not be 5v tolerant, because they are connected to GPIO pins, but there are FTDI boards that allow you to select 3.3v compliant levels for the RX and TX lines (and some that allow doing this while maintaining 5v on the VCC output).

If you are good at soldering, you could tack wires onto D1/PRTR5V on the top of the board, instead of using the points on the bottom of the board, although using a USB extension cable seems to be the easiest method.

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