[OZAPRS] Small GPS

[Andrew Errington]

On Mon, January 10, 2011 09:57, Andrew Rich wrote:
> The considerations I have struck are
>
>
> 1) Does the device do true RS232
> 2) Does the device simulate RS232 at TTL levels
> 3) Does the device do TTL but inverted for the USART in a MICRO
> 4) Does the device meet the minimum requirements for volts in a logic
> "high"
>
>
> I had to invert the TTL from the GPS 18 to make it work with the USART in
>  the 16F628
>
> I could bit bang but I am too lazy.
>
>
> Some GPS modules are now coming out uP happy and are already inverted.

These two from an NZ supplier might be worth looking at.  They both have
TTL options but the polarity is not clear (I understand entirely your
problem wrt RS232, TTL and inverted-TTL):

http://www.efrontier.co.nz/estore/product_info.php?cPath=2_3&products_id=77
http://www.efrontier.co.nz/estore/product_info.php?cPath=2_3&products_id=272

Another cheap and common device is this, but it's RS232 I think:
http://www.usglobalsat.com/p-57-br-355-gps.aspx

The prices at efrontier are very high.  I know you want to keep the
component cost down, but why not just two transistor buffers to invert Rx
and Tx data?  Here's an example:

http://www.ringolake.com/pic_proj/gps_trak/freetrak202.html

73,

Andrew
ZL3AME