用于将 GPS 坐标转换为 NMEA 格式的 AVR 代码

Question

I made an Android application that takes data from the GPS and sends it. It's picked up by aPC, and sent over USB to an AVR kit, which needs to convert the longitude, latitude format to NMEA format and return it back to USB. The message format is:

latitude='23.353434333' and longitude='45.34333345'

I need to convert the above message using an ATmega32 to NMEA GPS format, but since I don't know AVR programming, can somebody suggest how I can do it or the code for above?

Answer 1

That you have no experience with AVR programming has nothing to do with implementing NMEA. Knowing C however would help ;)

Your given representation latitude='23.353434333' and longitude='45.34333345' is called decimal degrees (your example is missing the N/S and E/W indication).

I assume you are aware that NMEA is a protocol specification, not just a coordinate format. The NMEA standard uses the following coordinate notation in the datasets:

XXYY.ZZZZ

This can be directly represented in the degrees minutes seconds format like this:

XX°YY'(0.ZZZZ * 60)"

So the conversion between the two is trivial, as well as the conversion from degrees minutes seconds to decimal degrees :

decimal degrees = degrees + minutes/60 + seconds/3600

So in essence you just have to perform the given conversions in reverse and you get your NMEA coordinate format.

A NMEA dataset looks like this:

$GPRMC,162614,A, 5230.5900,N,01322.3900,E ,10.0,90.0,131006,1.2,E,A*13

I highlighted the coordinate information in bold. Implementing the conversion is nothing special, while implementing the NMEA protocol requires some additional reading about the implementation details.

Answer 2

Convert a NMEA decimal-decimal degree value into degrees/minutes/seconds First. convert the decimal-decimal value to a decimal: 5144.3855 (ddmm.mmmm) = 51 44.3855 = 51 + 44.3855/60 = 51.7397583 degrees

Then convert the decimal to degrees, minutes seconds: 51 degress + .7397583 * 60 = 44.385498 = 44 minutes .385498 = 23.1 seconds Result: 51 44' 23.1"