Well, I agree with Michael somehow. If I was in your position I would do the following: Since you don't have to mess with many chips and all you need is a uC, as the main processor, and a USB interface plus some simple peripherals (LEDs, buzzer, matrix keyboard, radio link module with RS232 as you mention), it is easier to choose the proper uC (for me it is Cygnal if you need many I/O pins) and interface them to it. For the USB interface you can choose either a chip from FTDI or a USB-to-UART bridge like Michael and Erik proposed. You 'll see it want be something too difficult. You won't have to face many different, and in many cases difficult, protocols/buses. Just some simple LEDs, buzzer, etc. as you say. Imagine if you had to do with TCP/IP, ATA, wireless USB, etc. I believe you'll save time designing your own PCB, than loosing time searching for a ready one...