LPC17xx Virtual COM port - A USB CDC Class device library

With physical COM ports non-existent in laptops and fast disappearing on desktops, its a matter of immense convenience to embedded programmers if a chip has the USB interface.

The LPC1768 has a USB device interface and this library will allow you to use it as a virtual COM port. The library combines function from various sources which have been listed in the link.

Here's a simple example demonstrating the library. Check out the various functions offered in usbSerial.h

To build this example, first download and extract the latest project quick start code base. Then, download and extract to the same folder, the usbSerial library. The contents of main.cpp are as follows:

#include "LPC17xx.h"
extern "C" {
#include "usbSerial.h"
}
int main()
{
    int i=0;
   
    usbSerialInit();
    while(1)
    {
        VCOM_printf("\nLooping %d times. Press a key...",i);
        VCOM_getc_echo();
        i++;
    }
   
    return 0;
}


Download the latest compiled project here. Change the flash start address in the linker file(LPC17xx.ld) and re-build if you are using a secondary bootloader. I've made the changes for NXP secondary USB bootloader.

Windows will ask for a driver the first time the device is used. The .inf file needed is in the library folder itself. For those who might want assistance installing the driver,

Windows 7 lacks a terminal software. So, you'll have to use a terminal emulator if you use windows 7. Some popular ones are TeraTerm, RealTerm, and putty. Another one which caught my eye for its simplicity is Bray's Terminal.

Whichever you may choose to use, you will need to know what number was assigned to the LPC1768 COM port. This information can be obtained from Device Manager.

As can be seen above, COM7 is what i'll need to use for communicating with LPC1768.

References:
1. Code Red RDB1768 example projects.
2. ARM Projects by Martin Thomas