Basically, anything above, say 1.2 volts is taken as a logic "1",
anything
below (like ground) is a "0". That is how it can take 5 volt logic.
Ground
is always ground, and 5 volts saturates the input, but is still taken as a
high. As long as the GPS is putting out 1.2 to 1.5 volts (or so), it will
work.
BTW the MAX 232 chip converts 12 volt RS232 to ttl:
http://www.piclist.com/techref/io/serial/rs2322ttl.htm
Sincerely,
Dennis Ideue,
Advanced Merchant Solutions, Inc.,
A Registered Visa / Mastercard Independent
Sales Organization (ISO) for Columbus Bank
and Trust, Columbus, Georgia.
http://www.MerchantAnywhere.com
PalmSource Software Champion
Microsoft Mobile Solutions Partner
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-----Original Message-----
From: bounce-636821-60916@news.palmos.com
[mailto:bounce-636821-60916@news.palmos.com] On Behalf Of Luc Le Blanc
Sent: Wednesday, April 16, 2008 11:22 AM
To: Communication Developer Forum
Subject: RE: Expected voltage of serial signals ?
Dennis Ideue wrote:
> 3.3v and ground (low-level TTL), although the devices can talk to, and
> receive 5v TTL logic signals.
Thanks for the prompt answer. I'll pass it on to a hardware developer
wishing to exchange data with my app.
But out of curiosity, how can my GPS, powered by 2 AA batteries, maintain
3.3V? Unless they raise the voltage, which I doubt, it's probably more like
2.8 - 3V.
Regards,
Luc le Blanc
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