USB output with RCM5700 Interface Board in non-programming mode

Hey everyone, thanks for making this a great forum.

I have a Rabbit MiniCore RCM5750 on a Development Kit Interface Board (part#20-101-1236). Programs fine and everything works cool.

I would like to use the USB UART connected to serial port A (typically used for programming & debugging) as a diagnostic output for field service technicians while the board is in RUN mode (ie: JP1.Smode is NOT jumped). On the surface, it seems perfect: if a tech wants to know what’s going on with my firmware, connect a PC to the USB port of the Interface Board, crank up HyperTerm and configure it for COM6 (or whatever is shows up as), and check out whatever my firmware cares to tell, such as version numbers and error codes.

Unfortunately, opening serial port A and outputting characters does not seem to be getting out through the USB-UART.

Q1: Is this even possible with the hardware? Is the USB-UART even connected to serial port A when the interface board is jumped to RUN mode? Schematic looks cool for this, but maybe I’m missing something.

Q2: If I’m on a worthy path, is there more configuration that I must do besides opening port A at my desired baud rate and sending characters? I’ve programmed the other serial ports before (B, C, D, …) and find it exceptionally easy.

Thanks for taking the time to read and respond. I promise to do the same when I have something to add.

Can you not just use printf to write info to port A in run mode? it should be set up as the console.


Hey Peter, thanks for the advise. Unfortunately that does not appear to work, at least not for me. Does this work for your firmware?

Here’s what I did: Within Dynamic C and RCM5700 in program mode on the Interface Board, I can upload firmware and see debug “printf” output fine in the console window. Close Dynamic C, remove jumper for Run mode, start HyperTerm on the PC, set to COM6 (USB-UART on the Interface Board) and 115200 baud, and reset the RCM5700. I can see that the firmware is running (I flash the on-board LED) but no output occurs to that COM port.

Am I missing something here?

As stated in the initial post, I have also tried to open Serial Port A in my firmware, configured to 115200 baud, and write out to the serial port using serAwrite. No dice there either.

Thanks again for your post,

Have you had a look at the stdio_serial.c sample program in the samples directory?

That shows how to set up printf to output to the serial ports in run mode.