How to interface with a USB-VCOM IC like those from FTDI?

Mbed OS
1

Hi,

I am trying to communicate with a FT231X from FTDI with MBed. FT231X is a USB-VCOM chip. It will emulate as virtual COM port when connected to Windows. I assume I will need to use USB Host and in full speed mode.

Between USB-CDC and USB Serial, which one is the correct one to use?

Thanks in advance.

2

Hello,

I am not sure I understand, but FTDI converts data from a device’s UART to USB of a host and vise versa of course.
On Mbed target side you have to connect it to an UART and chose Buffered/UnbufferedSerial.

  • can be with or without flow control (2 or more pins)
  • The baud rate does not need to be set inside the chip, it has autodetection. Only on the host side.

I do not know what a target do you use, but for example I chose Nucleo-F429ZI. With that board and USB-CDC or USB Serial you can achieve similar/same result like with FTDI, I think.

If you want to set some data inside to FTDI memory and so on. These APIs are insufficient for this. Mbed provide only USBDEVICE APIs not HOST.

BR, Jan

3

It is an odd use case. The problem is I have to communicate with that FT231X chip from Mbed boards via USB. It would be a lot easier if I have access to the UART on the other side of FT231X, but I don’t.

4

You’ll probably need to implement a custom USB driver, because, IIRC, FTDI’s chips use a proprietary USB interface. Maybe the Linux FTDI driver would be useful as a reference?