I have been trying to get the serial ports working on an Olimex LPC-P2103 development board. First I got UART0 working, which was straightforward; everything works as expected. Then I started on UART1.
After soldering a 3-pin header onto the board, I found that UART1 can transmit just fine but cannot receive anything. This was puzzling because the same code works just fine for UART0. I spent hours looking for bugs in my driver code, but I just couldn’t figure out what was wrong.
Then I thought maybe I’d damaged the board when I soldered the header on. I began to trace back from the RX pin on the header, and discovered there is no continuity between the MAX3232 driver chip’s R2OUT pin and the P0.9/RXD1 pin on the micro. Looking at the schematic, the letters “NC” appear next to R29 - could that stand for “No Connection?” Sure enough, when I looked at the board, there is a pair of empty pads where R29 should go.
Can anyone explain why Olimex would put everything in place for two fully-functional UARTs and then leave out this one critical little component? Maybe it’s obvious to those of you with lots of embedded experience, but for me it was completely unexpected and caused me to waste a lot of time chasing down a non-existent coding error.
More importantly, how do I make it fully functional? Can I simply solder a short piece of wire across the two empty pads?
Thanks for any insight you can provide. 