The circuit it is self is pretty simple, take in the data on one pin, parse it, format it and then display it to a 4×20 LCD module . That is the basic idea, but I might add in somthing like a mechanical encoder that would allow for changing options or changing settings in the display unit. This might be as simple as a SPDT switch if the options are as simple as two settings.
This project is based on a PIC16F84
Here is the schematic. I used a 4 Bit configuration for the LCD to PIC wiring. This all that would be required for this application. Plus, the 16F84 does not have a lot of port pins, so I have to use them wisely. You can see the GPS data is comming in on PORT A PIN 1. The LCD data goes out on PORT B PINS 0-3. The LCD’s Register Select (Rs) is on PORT A PIN 2 and the LCD’s Enable (E) is on PORT A PIN 3. In the original design, I had included a MAX232 level converter to do the TTL to Serial conversion before it came into the PIC. I found a serial routine that did software inversion and allowed me to eliminate the MAX232, so one less part. This is really nice because basically the entire circuit could be layed out on a board the same size as the 4×20 LCD.
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