2 Application questions about mesh products

[ScruffR]

@TomEldredge

Can a xenon run application code without being connected to the cloud and without trying to connect to the cloud?

Yes, when using a non-AUTOMATIC SYSTEM_MODE

@TomEldredge

Mesh device charging circuit. The mesh products can run with the Li battery, but the Li will have to be charged when not connected to the PC. Do you apply the external charging voltage to the USB pin? Do PC’s usually have diode protection on the USB to prevent conflicts with other external charging voltages?

You can connect a USB charger or supply 5V to the VUSB pin.
The docs do feature a block diagram that shows the input power block
https://docs.particle.io/datasheets/mesh/xenon-datasheet/#block-diagram

@TomEldredge

Presently we use the Electron and I think we charge through the VM pin

What is the VM pin? Do you mean Vin?
On mesh devices VUSB is the same thing as on Gen1&2 devices Vin but there is no protection diode between USB and Vin to prevent back-feeding into the USB port.

There are some posts that address the potential back-feeding and possible workarounds (if needed)

Power to boron / xenon

Unlike the Electron/Photon on mesh devices there is no protection diode between the USB connector and VUSB. So when supplying power both ways you need to be extra careful (others even suggest to keep it mutually exclusive) but grounding EN does not mitigate the potential danger for your USB port in case of back-feeding via VUSB in any way. What you can do is to manufacture a custom USB cable which disconnects the USB Vcc line. I’ve 3D printed myself a little insulator inlay for the USB-A conn…