slowest practical baud rate?

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I'm trying to run a PIC12F675 with an external 32.768KHz crystal to maximize
battery life.

I would like to interface to the part with a serial interface.  I've tried
300 baud and 110 baud (no partiy, 8 data, 1 stop) but they didn't work.  300
baud gave invalid character returns and 110 baud didn't show anything.  I'm
interfacing with a HyperTerminal session.   I have serial input going in to
pin A3 (I declared NOMCLR in the fuses) and output going out of pin A2.

I can see the program running (as indicated by toggling of a heartbeat
indicator) but the code does not recognize the serial input characters
correctly.

Has anyone tried this "extreme" condition or am I just "spitting into the
wind"? :)

Thanks.


Dave



Re: slowest practical baud rate?



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Don't bother with hyperteminal - google for "bray terminal" - this lets you see
precisely what is going on and allows you to control handshaking pins.
I assume you are using a simple RS232 interface powered from the port?


Geo

Re: slowest practical baud rate?



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Thanks for the response.  I'll check into the "bray terminal".

Yes... I have a simple three-wire interface with a ICL3232 (MAX232 clone).
I'm running the whole system on two AA cells (about 3.2VDC with a
multimeter).

I have been trapping the log from the HyperTerminal session to a text file
that I examine in hex after the fact.  The characters (when I see them)
don't look anything like what was sent.

Dave



Re: slowest practical baud rate?


SNIP
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Normal Max232's won't run reliably at 3.3 V, as I found out recently. 2
solutions- use a 2N7000  pulled to RST and set RST true ( works fine for me)
or use a true 3.3 v compatible mrs232 chip......



Re: slowest practical baud rate?



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The Intersil ICL3232 is rated to run from 3.0VDC to 5.5VDC, it only draws
1uA quiescent current, and it takes 0.1uF caps.

I've never had a problem.   Good chip.


Dave



Re: slowest practical baud rate?



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You can see hex directly with "Terminal".
You can also set parity data and stop bits BUT - I have just noticed that it
lowest baud rate is 600...
An alternative (on my desktop) might be TeraTerm Pro
http://hp.vector.co.jp/authors/VA002416/teraterm.html
which does list 110 baud but I am not sure of its hex capabilities.

Geo

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