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2 serial links over USB?

Topic last updated 18 Jul 2016, by Andy A. 1 reply
Leon M
17 Jul 2016

Hello,

Is it possible to put 2 serial links over the USB device interface of the MBED? (not the debug interface of course). I want to declare 2 "USB Serial", but it doesn't work.

My goal is to use 2 interfaces for a homemade radio modem, with a custom protocol.

  • One of the 2 serial link would transport "SLIP" connexion (Serial Line IP) between PC and Mbed.
  • The second would be connected to a terminal, so that the user can manage the modem.

I don't want to use the debug interface for the second port, because I want to port the program to a microcontroller without the debug chip (LPC1768/69).

Thank you for your help!

Leon.

Andy A
18 Jul 2016

While it may well be possible it would require custom drivers on the PC side of the link.

The more standard way to do this would be to use the normal modem escape sequence of +++AT<cr> to enter command mode

This does mean that you can't configure the modem at the same time as passing data but that is rarely an issue.

If you must have two ports you could always use an FTDI usb to serial chip con convert one of the uart ports to USB, this is effectively what the debug port on the module is doing.