[RTEMS Project] #3858: PC386 BSP serial console outputs garbage on real hardware

[RTEMS trac]

#3858: PC386 BSP serial console outputs garbage on real hardware
------------------------+------------------------------------------------
  Reporter:  Lou Woods  |      Owner:  (none)
      Type:  defect     |     Status:  new
  Priority:  normal     |  Milestone:
 Component:  bsps       |    Version:  5
  Severity:  normal     |   Keywords:  console, serial, pc386, corruption
Blocked By:             |   Blocking:
------------------------+------------------------------------------------
 = Problem description
 When the RTEMS ticker test, possibly others, is started with the
 -–console=/dev/com1 command line argument the output to COM1 using the
 pc386 BSP on real hardware the console output is invalid/garbage
 characters instead of the expected ticker output.  The serial output looks
 like a baud rate mismatch.

 Ticker works as expected when left to output to the VGA console.

 = Test configuration
 == Hardware tested
 Winsystems EBC-855 (Intel® Celeron-M ZC Dothan 1GHz)
 Dell Optiplex 755 (Intel Core 2 Duo)
 == Hardware configuration
 *The PC386 target COM1 is connected to a Raspberry Pi 3 with a Keyspan
 RS232 serial to USB converter. (This hardware combination works with other
 boards)
 *The PC386 is connected via a network to the Raspberry Pi 3 running a TFTP
 server that provides the boot images.

 == Software configuration
 * RTEMS Master e22554535796fc29a7ed7c5e2338128e324a621d
 * RTEMS configuration
 {{{#!bash
 ../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 BSP defaults COM1 to 9600bps 8-N-1 with no flow control.
 * The Raspberry Pi serial host is running Debian (Raspian) Stretch
 * The executable is booted from the Raspberry Pi TFTP host by chain
 loading RTEMS via IPXE

 == General Notes
 The test setup's serial connection was verified to work using the Optiplex
 755 running Windows and the same hardware components with a simple Foxterm
 serial session.

 == Things attempted one at a time
 * sweeping the baud rate on the serial host while holding the board at
 9600 8N1
 * trying different baud rates in lock-step, target 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;
 currently haven’t tracked down the error.
 * 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

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Ticket URL: <http://devel.rtems.org/ticket/3858>
RTEMS Project <http://www.rtems.org/>
RTEMS Project