Proper way to connect FTDI cable to Xenon

Hardware
1

I have a Xenon that is connected to a PC via an FTDI RS232 cable (3.3V). The Xenon is powered from an external source via its VUSB using 5V.

What is the correct way to connect the FTDI’s VCC and GND cables? For a common ground, GND should be connected to Xenon’s GND? What about the VCC cable? Do I connect it to the 3.3V pin on the Xenon or leave it disconnected?

Thanks in advance for the community’s help.

2

It depends on the adapter. For example, the SparkFun adapter has a switch to determine how to power the chip.

  • If USB powered is selected, then the converter is powered by USB and VCC does not need to be connected. Be careful, however, that your adapter does not generate TX-O at 5V when you do that, because the mesh devices are not 5V tolerant.
  • If host powered is selected, then the converter is powered by VCC and you connect that to 3V3 on the Argon/Boron/Xenon.

If there is no switch but there’s a VCC pin, then you probably need to connect RX, TX, GND, and VCC to 3V3.

Of course GND always needs to be connected.

3

Thank you @rickkas7.

There is no switch on the cable. I made sure this cable is the 3.3v version.

In testing, I did not connect the VCC cable to the Xenon. It works fine, however, I noticed that sometimes, the Xenon would not restart when recycling power (led does not light up at all). In this case, the only was to restart it is to unplug the FTDI cable.

Does this mean that the cable VCC needs to be connected to the 3.3 V pin on the Xenon?

I was hoping to avoid that because if I need to recycle power to the Xenon I would also have to unplug the cable and then replug it as the Xenon is powered separately but would be getting power from the cable.

I had to power the Xenon separately via the VUSB pin with a custom feather as I need 5V for a sensor.

I would really appreciate your input and thanks in advance.