Serial Tool Aborts or Reset

When I issue an at+join command, the node joins but the serial port tool locks up or crashes. When I connect back in board resets and shows not joined so I’m not able to send data.

This seems to be a basic functionality that should work, is there a know issue with the serial port tool or any recommendations or workaround?

Serial Port Tool: V1.2.1
Module RAK4200



I’d suspect that the board is asking for more power than your USB can give.

I use the serial tool with a 4200 on both an EVB and directly using a USB-serial convertor to a breakout board with out issue.

Are you using a 4200 on the EVB? Have you installed the USB-serial driver? Can you try a different USB port or different computer?

I had the same suspicion. A power brownout making the module reset. That shouldn’t crash the serial port tool though but maybe it powering down the whole USB adapter where the serial port is removed from the PC.

I will monitor power, I think you 've pointed me in the right direction. Thanks for the suggestion.

If you’re doing something like stealing current from the on-chip regulator of an FTDI USB UART (or its clone) then browning that out with LoRa radio transmit current would cause the USB device to fail, and the OS to throw errors at any program trying to use it.

You probably can power the board from USB, but you should use the USB VBus and a distinct regulator, not the low-current output of a USB-UART board which can only spare a few milliamps.

It is also theoretically possible that a poor USB implementation could be sufficiently disturbed by radio frequency energy from transmission to drop the connection - not likely, but still possible. Consider trying other (shorter) USB cables. If you were using a hub, try it without, if you were not using a hub, try it with one, try a different computer, etc.

Ideally a serial line connecting to a radio device would have ferrite beads or small chokes to keep undesired energy from coupling that way; typically this is done to protect the radio receiver from computer noise, but technically it works both ways.

And please do clarify if you are using the EVB or your own USB UART solution.

From memory, FTDI can only do about 50mA whereas the other chips can usually delivery >250mA.

Confirmed. The USB adapter browns out with the radio TX current surge.

I’m using our own board with a CH340 USB adapter. When powering through external source the transmission is successful.

Thanks for the help.

Hmmm, most of my USB-Serial adapters are CH340 (about 5 in front of me right now) - which can do 300mA - with a Tx typically at 140mA you must have other stuff running - LEDs, sensors at full power and so forth.