[OZAPRS] Small GPS

[Gerard Hill]

Well VK2SKY and VK3JFK are subscribed to this list.
There would have to be others out there too.

With RS232 signalling, you could mostly get away without using negative 
voltages because the popular receiver chip, the MC1489 had a logic 
switching threshold of about 1 volt with some built in hysteresis. This 
was used in the PC and many other places.

The chip also had the (possibly unfortunate) capability to shift the 
threshold to a different voltage. Some purist design engineers shifted 
the threshold to 0 volts which stuffed up compatibility with a lot of 
devices that generated no negative rail. Certainly, some PCs had been 
designed by the purists and then didn't work with some devices.

Cheers ... Gerard, VK2IO

On 10/01/2011 8:28 PM, Andrew Rich wrote:
> Who's Richard ?
>
>     ----- Original Message -----
>     *From:* Chris Herd <mailto:zl2tch at gmail.com>
>     *To:* 'Andrew Rich' <mailto:vk4tec at tech-software.net> ; 'Australian
>     APRS Users' <mailto:ozaprs at aprs.net.au>
>     *Sent:* Monday, January 10, 2011 7:12 PM
>     *Subject:* RE: [OZAPRS] Small GPS
>
>     Hi Richard
>
>     Try here.
>
>     http://www.sparkfun.com/categories/4
>
>     Chris
>
>     *From:*ozaprs-bounces at aprs.net.au
>     <mailto:ozaprs-bounces at aprs.net.au>
>     [mailto:ozaprs-bounces at aprs.net.au] *On Behalf Of *Andrew Rich
>     *Sent:* Monday, 10 January 2011 1:08 p.m.
>     *To:* Australian APRS Users
>     *Subject:* [OZAPRS] Small GPS
>
>     Hello looking for a tiny GPS for a project.
>
>     The ones that have a patch antenna and electronics on the bottom.
>
>     Some of them say "TTL" and some say "RS232"
>
>     RS232 is pretty obvious.
>
>     I am using it with a PIC micro which is idle high in the USART.
>
>     Any suggestions ?
>
>     At the moment I have a GPS 18 which has to go through a MAX232 to go
>     from suido "RS232" (TTL) to be "flipped" for the USART in the PIC.
>
>     - Andrew VK4TEC -