On 27/11/2010 06:22, Dena Meier wrote:
> Thank you for your ideas.
>
> I have tried loopback with hyperterminal, and it works just fine.  Huh?  =
I
> got
> echoes of characters at 57600 baud.
>
> The PICDEM PIC18 Explorer Demonstration Board has both a standard 9 pin
> RS-232 interface
> and the USB serial interface (USB B connector).  There are two jumpters
> 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
> interface.
> The firmware works very fine with the RS-232 interface.  It works very
> well at 57600 baud.
>
> I calculate a pulse train coming out of the PIC18F8722 TxD port (approx.)
> 2.26 ms long.
> I measure with a scope approx 2.2 ms.  The pulse trains occur once per
> 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
> 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
> TxD.  Hyperterm
> proved this.
>
> But the PIC18LF2450 RxD does not like (work with) the TxD of the
> PIC18F8722.  I am getting
> signals from the PIC18F8722 TxD to the PIC18LF2450 RxD.  My scope proves
> that.
>
> I had tried a split configuration.  I configured the PC software to use
> USB COM4 for sending
> commands/data to the PIC18F8722 (thru the USB).  I configured the PC
> software to receive
> data from the PIC18F8722 via RS-232 COM1.  The receiving of data from the
> RS-232 COM1 works
> fine, even when I connect the PIC18LF2450 RxD to the PIC18F8722 TxD.  Thi=
s
> checks if the
> PIC18F8722 is pulling down the line.  It is not doing so.  It just seems
> that data from the
> PIC18F8722 is not being processed by the PIC18LF2450.  This split setup
> 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
> 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
> assembly.
>
> More ideas would be welcome.  The USB serial interface uses the built-in
> Windows communications
> class USB driver.  This is what Device Manager tells me.
>
> Thanks everyone!
> Dena Meier
>
>

Not sure if I understand exactly, so sorry if I have missed something..
If connecting the 2450 Tx to Rx works, but the 8722 does not, then it=20
would seem to be an issue with how the 8722 is sending it's data - have=20
you got it set up for correct polarity/stop bits etc?
I assume there should be some notes with the required info regarding how=20
the 2450 is set up, so maybe have a look there.
Also, try simplifying the data being sent in case you are sending it too=20
fast - just send one character every second or something, not a stream.


--=20
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