[OZAPRS] Small GPS

[Andrew Rich]

The reason I ask is there is TTL and there is TTL

My Garmin GPS 18 5Hz puts out TTL instead of RS323.

In that it goes from 5 volts to 0 volts and tricks the RS232 drivers into 
thinking it is RS232 levels.

Then there is the PIC TTL.

I have to invert the TTL from the GPS 18 to feed into the PIC

The PIC wants a zero to be a high and then swing low.

I see some "uP friendly" GPS around that do this inverted TTL - feed 
straight into the PIC

Trying to get my component count down.

- Andrew -

----- Original Message ----- 
From: "James Cameron" <vk2lqz at wia.org.au>
To: "Andrew Rich" <vk4tec at tech-software.net>; "Australian APRS Users" 
<ozaprs at aprs.net.au>
Sent: Monday, January 10, 2011 10:15 AM
Subject: Re: [OZAPRS] Small GPS


>I would expect a PIC with a USART to be connected directly to a TTL
> serial port on a GPS, provided the GPS and the PIC operate on similar
> levels.  That is, a GPS TTL port may actually be a 3.3V limited port, in
> which case the PIC should be operated from 3.3V as well.  Unless you add
> level buffering.
>
> -- 
> James Cameron
> http://quozl.linux.org.au/
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