What is a debug port and is it required for proper A13 board operation?

[mikenycz]

I am trying to communicate between the Olimex A13 computer and a PC using the UARTs on the A13 board. I am running Debian Linux and I am using both UARTs (ttyS0 and ttyS1, UART1 and UART3 resp.) On UART3(ttyS1) I can communicate (send and receive from the A13) with no problems. When I try to communicate on UART1 (ttyS0) the send works perfectly however the receive loses the 1st byte coming in (sends an error message to the console on the PC saying that the character that is typed is not a command) and then all future characters are received correctly.

If I switch from receiving to sending and then back to receiving the same occurs. If I stay in receive mode I can receive characters for as long as I want with no data loss after the first lost byte.

As I mentioned earlier I do not see this issue on UART3 (ttyS1). I started looking for reasons why the two ports are different. I used the same program to set up send and receive for both UARTS (I used the same program, just switch the pointer to ttyS0 or ttyS1) so the problem is not in the program setup. One thing that I did find when I typed the command dmesg |grep tty I get the following:

[    0.000000] Kernel command line: console=ttyS0,115200 root=/dev/mmcblk0p2 roo twait loglevel=8 panic=10
[    0.446780] sunxi-uart.1: ttyS0 at MMIO 0x1c28400 (irq = 2) is a U6_16550A
[    1.114996] console [ttyS0] enabled
[    1.154643] sunxi-uart.3: ttyS1 at MMIO 0x1c28c00 (irq = 4) is a U6_16550A

I see that ttyS0 has the "console [ttyS0] enabled" associated with it where the ttyS1 does not. I was wondering what the "console [ttyS0] enabled means? In the fex file I see that ttyS0 is designated as a "debug port". Is this the console that is referred to in the dmesg message above? If so, can I run the machine without a debug port? If someone could explain what the debug port does it would be great.

Thank you,
Mike Nycz