http://www.electronic-engineering.ch/microchip/projects/projects.html#simple_rs232


a good site to start. By the way are you using TTL
between the DB-9 connector and PIC? Use Max232 as the
TTL module between them. The only conclusion that I
can come out with is that the 9v is from the computer
serial port rite? If so DO NOT do it again. Wire your
project correctly without the chance of short
circuiting. Follow the site recommendation. 

John


--- Ben Sinclair <ben@bensinclair.com> wrote:

> I'm fairly new to PIC development and am just trying
> some things out
> right now. I want to get my PC and PIC talking over
> a serial port and
> am having trouble figuring some things out. It's a
> 16F84A.
> 
> I'm using a DB-9 connector from my PC to the PIC,
> with the TX and RX
> pins connected to I/O pins on my PIC. What I'm
> having trouble with is
> pin 5 on the DB-9, which is apparently should go to
> ground.
> 
> If I have pin 5 connected to the same ground as my
> PIC, the PIC will
> not start. I have a serial LCD hooked up for
> debugging, and nothing
> appears. If I disconnect pin 5, the PIC will start
> up just fine and
> display my debugging output.
> 
> My test program is also supposed to send text to the
> PC via the serial
> port. If the serial ground pin is not connected, and
> the PIC starts,
> nothing is received by the PC. If I connect the
> serial ground to the
> PIC ground after it has started, one of the
> following happens: the PC
> will receiving data just fine, the PIC will reset,
> or the PIC will
> just stop doing anything.
> 
> I'm confused on what I should be doing with the
> ground pin on the
> serial port. Should it be on the same ground as the
> PIC? If I connect
> my multimeter to pin 5, then to the PIC ground, I
> see it's putting out
> 9V. Does that seem normal? It seems like I probably
> shouldn't be
> connecting 9V to the same ground line that the PIC
> connects to, but I
> don't know for sure.
> 
> Thanks!
> 
> -- 
> Ben Sinclair
> ben@bensinclair.com
> -- 
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
> 


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