Thank you for your ideas.

I have tried loopback with hyperterminal, and it works just fine.  Huh?  I =
=20
got
echoes of characters at 57600 baud.

The PICDEM PIC18 Explorer Demonstration Board has both a standard 9 pin =20
RS-232 interface
and the USB serial interface (USB B connector).  There are two jumpters =20
that select the
RxD and TxD for either interface to use.

I wrote the firmware for the onboard PIC18F8722 to use the 9 pin RS-232 =20
interface.
The firmware works very fine with the RS-232 interface.  It works very =20
well at 57600 baud.

I calculate a pulse train coming out of the PIC18F8722 TxD port (approx.) =
=20
2.26 ms long.
I measure with a scope approx 2.2 ms.  The pulse trains occur once per =20
second.  This
is binary data being sent out of the PIC TxD port.

This is strange.  All of my PC software (a user interface) and my PIC =20
firmware works
very well with the RS-232, not a single problem.

The PIC18LF2450 works when you loop it back, i.e., connect its RxD to its =
=20
TxD.  Hyperterm
proved this.

But the PIC18LF2450 RxD does not like (work with) the TxD of the =20
PIC18F8722.  I am getting
signals from the PIC18F8722 TxD to the PIC18LF2450 RxD.  My scope proves =20
that.

I had tried a split configuration.  I configured the PC software to use =20
USB COM4 for sending
commands/data to the PIC18F8722 (thru the USB).  I configured the PC =20
software to receive
data from the PIC18F8722 via RS-232 COM1.  The receiving of data from the =
=20
RS-232 COM1 works
fine, even when I connect the PIC18LF2450 RxD to the PIC18F8722 TxD.  This =
=20
checks if the
PIC18F8722 is pulling down the line.  It is not doing so.  It just seems =20
that data from the
PIC18F8722 is not being processed by the PIC18LF2450.  This split setup =20
works fine also
and sending commands to the PIC18F8722 via USB works fine.

I do not have source code for the PIC18LF2450.  It came preprogrammed by =20
Microchip.  They
have only provided the HEX file in the documentation files.

I could debug, but I would have to debug maching language, not even =20
assembly.

More ideas would be welcome.  The USB serial interface uses the built-in =20
Windows communications
class USB driver.  This is what Device Manager tells me.

Thanks everyone!
Dena Meier


--=20
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