PC386 BSP Serial Console Problems

[Lou Woods]

Hello all,

I've been working on getting an old PC based SBC (Winsystems EBC-855) up and running in our RTEMS lab and I'm having a problem getting the serial console to work.  The VGA console is works, however when the executable is started with the -console=/dev/com1 command line argument the output to COM1 is unprintable/incorrect characters AKA garbage.  The serial output looks like a baud rate mismatch.  It is almost like baud rate is just a little off.  Unfortunately, I don't have the means to measure the actual baud rate.

Has anyone done this recently?

I'm using the latest RTEMS head, pc386 BSP, and ticker test.  I've been testing this configuration by chain loading TFTP via IPXE which seems to work well.  In order to verify my end to end configuration works, I also tested this on a Dell Optiplex 755 Intel Core 2 Duo computer.  With this configuration I was able verify the same serial corruption exists on this computer under RTEMS and I was able to demonstrate that while running Windows I could use the same serial port, cabling, baud rates and serial host computer for serial communications.

The BSP is configured to use 9600bps 8-N-1 with no flow control by default.
Here is how RTEMS is configured:
../rtems/configure --target=i386-rtems5 --enable-rtemsbsp=pc386 IDE_USE_PRIMARY_INTERFACE=0 --prefix=/home/woods/pc386/bsp-install/ --disable-networking --enable-posix --disable-smp --disable-multiprocessing --enable-tests --enable-cxx --enable-maintainer-mode

The serial host is a Raspberry Pi 3 running Debian (Raspian) Stretch.

These are the things I've tried, not in combination:
- sweeping the baud rate on the serial host while holding the board at 9600 8N1
- trying different baud rates in lock-step board and serial host.
- various combination of hardware flow control, parity, word size, stop bits.
- Winsystems board talking to a Windows PC running Foxterm.
- Running RTEMS 4.11 branch with current i386 toolschain - exe hangs, haven't tracked down error yet.
- COM2 port on the Winsystems board.
- Changing the clock rate for the baud-rate divisor in RTEMS
- 3 wire serial communications with RX, TX, and GND

Does anyone have any ideas?  I will open a ticket on this as well.

Thanks,
Lou Woods
OAR
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