So this is Arduino related and not really about Perl, but all the code I've been hacking on prototyping in Perl and porting to C has gotten me a lot of progress. I suppose it is Perl related to some degree, as if it wasn't for me knowing Perl and all the experience I've gained about writing C/XS, I wouldn't be here.

I have the GPS connected to my Trinket Pro on battery, with a GPS unit and a 0.96", 128x32 pixel OLED screen. I also have a button to switch between the "home" display contents, and the "return" display contents, and a button that writes to EEPROM that saves the coordinates of the current location.

The idea is that I can press the "save" button before going on a long hike, and turn the unit off. Then, if I ever get lost, I turn it back on, press the "return screen" button, and it guides me back to my starting location. Here are the screen layouts (in all cases I obscure some of the numbers as to not give out my home location :) Also, all coordinates have been shaved to 5 decimal points which is one metre. We don't need to be more precise than that, so it allowed me to shave some screen area) All of the N|W locations are generated dynamically based on whether the headings are negative or positive:

Home display. Top line is the current date and time in UTC. Second line is fixed-width north heading along with current heading (direction). Third line is fixed-width east heading, followed by the number of satellites we're currently locked onto. Fourth line is altitude, followed by current speed in KM/h.

17.06.03 21:17:16 UTC
N:051.11111 H:288
W:114.11111 s:6
A:1090 S:0.00
[download]

Return screen. First line is fixed-width north point of the destination we need to return to, followed by the distance in Km. Second line is the fixed-width west point we're returning to, followed by the direction in degrees we need to travel. Third line is the fixed-width north point that we're currently located followed by our current heading in degrees, and fourth line is our fixed-width west point followed by our current speed of travel in Km/h.

N:050.95355 K:38.687
W:114.58056 D:244.96
N:051.11111 H:288.07
W:114.11111 S:0.00
[download]

I have manually saved the coordinates of a location I'm driving to tomorrow (Bragg Creek, Alberta, Canada), and am going to give it a test run on that driving distance. Later this week, I will go for a hike about 8km and test the actual intended functionality. For now, I'm just going to do code cleanup, fix up a couple of tiny things, and if it all works after my tests this week, I'll be contemplating how I want to package it, and solder everything together.

I have not converted the awesome magnetic declination code into C yet, so the direction has not been calibrated. I'll hack together that code after the unit is packaged and field ready, before my first real life tests of it.