When using the AM4 for a GPS application, please note that the current generation 4.X operating system (firmware) requires that you use a full file name reference in your GPS playlist. That is, even if using our "8 dot 3" file-naming convention, the full file name including extension is required, not just the significant numerical digit. For instance, while our regular serial control protocol allows the use of 1PL to play file snd00001.mp3, the GPS playlist will require the entire snd00001.mp3 name in the Data1 field of GPS Builder. Personalized literal file names are also allowed; such as, MySoundClip.mp3, just so long as you include the extension and do not have any internal spaces in the name.
Also new to the AM4 for OS 4.X is the elimination of the CF card Write Protect feature. This ability is no longer supported and position 3 of the DIP switch is now undefined. So, after setting up your AM4 and preparing it for GPS use in your vehicle, make sure position 3 of the DIP switch is up for OFF, and make sure position 4 is down to turn GPS mode ON.