Is the PIC taking readings while the transmission is going on?  And if so,
is it interrupt driven?
If it is, you may be getting a corrupted return address, or you might get
data that the PC interprets as new line.
Are you using any sort of flow control between the PIC and the PC?  If not,
the above scenario becomes even more likely.
Just food for thought.

Jim

-----Original Message-----
From: piclist-bounces@MIT.EDU [mailto:piclist-bounces@MIT.EDU] On Behalf Of
Oli Glaser
Sent: Saturday, September 11, 2010 5:39 PM
To: Microcontroller discussion list - Public.
Subject: Hyperterminal and Max232 to PIC16F

Hi all - I have some work to finish a 16F temperature logging project for=20
someone (paid for a working version within the next 3 days)

It is using a PIC16F877, 4-line LCD with 4 buttons attached to the DB4-7=20
lines, 4 Maxim DS18B20 temp sensors, a couple of 32KB I2C eeproms, a MOSFET=
=20
to switch the LCD off when the PIC sleeps between readings (every hour for=
=20
at least 10 weeks) and a Maxim DS1307 RTC to timestamp and trigger the=20
interrupt to wake up and take reading.
All is working reasonably for and has been for a while on a breadboard, but=
=20
the chap I'm doing it for has it's own board that has been fraught with=20
problems from the start (I offered to do the whole thing myself and send it=
=20
fully working to him, but he wants to do it this way, which means I have to=
=20
write code, then send it to him and debug remotely...)

To get to the point - we are using a Max232 to Hyperterminal to upload the=
=20
data to the PC. I was using the PicKit2 Uart tool with no problems at all,=
=20
but with Hyperterminal things behave strangely - it gets to the end of the=
=20
readings (say 100 for now) then the cursor files down the screen with=20
newlines and cannot be stopped, like it loses itself. At this point I get a=
=20
"serial not present" message on the LCD (I show a message on=20
connect/disconnect)
The odd things the PIC, carries on with no problems - it does not hang, and=
=20
will carry on taking readings if they are activated. Putting a scope probe=
=20
on the Tx output pin of the Max232 though appears to show data still being=
=20
sent, even though the PIC is NOT actually sending anything and proceeding=20
normally??
I am not very experienced with Hyperterminal, or indeed RS232(before my tim=
e

really - I have always used USB) but as this is not my project I have no=20
choice. I know there is better software available but would like to know=20
what is going on with Hyperterminal, just in case he insists on using it.
I am thinking it may be something to do with not using a null modem cable?=
=20
the PC thinks it's talking to a modem and expects some handshake at the end=
?
Any suggestions as to what is causing this would be great - by the way, I=20
can send one or two lines okay to the PC, it seems to be just when a lot of=
=20
data is sent that it does this.
Any ideas?
=20


--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.