This is a program that emulates the functions of the Photo GPS interface on your PC.
Please note that is an early beta and error handling is minimum
The program acts a state machine, assuming input from the GPS and outputting formatted strings when requested by the camera.
The user interface is very straight forward and can be divided into 4 areas
The board emulator, the GPS emulator, the Communication logging window and finally the program setup.
The On/Off button acts as a power switch. Pressing it once activates the board and the power led lights up.
From this point on the board emulator can respond to camera requests.
Pressing it again shuts off the board and there will be no responce from the board to the camera.
The GPS lock led, displays the validity of NMEA data, coming from the GPS. In the actual board this led tells the user if the GPS has a valid fix, without having to look at the GPS screen, in the software version it has a rather cosmetic function :-)
This block provides NMEA data to the board state machine. At this stage the user can change only the UTC date and time and select whether the data will look valid to the board state machine or not.
Below its a gray area that will be used in the future for selection of files containing NMEA dumps.
Communication Logging Window
All actions of the board state machine that are relative to the communication with the camera are displayed in this window. These actions include the opening/closing of the serial port, receipt of commands by the camera and the replies to the camera.
This will be of help during the debugging of scripts
Two are the only parameters that can be set by the user.
Which comm. port to use for communicating with the camera and the format of the "No GPS fix" sentence.
The first is rather easy to understand so let's see a few details about the second.
Unfortunately the Digita scripting language is rather limited in the handling of strings, creating a problem when the user tries to take a picture and the GPS has not a valid fix yet.
This is due to the fact that the function that inputs characters from the serial port expects a pre-defined numbers of characters and exits with an error if this number is not received before the function times out.
Since all of the replies by the Photo GPS interface are of fixed length and longer than 20 characters, this creates a problem with the "No GPS fix" sentence, which might be returned by the Photo GPS interface if the GPS receiver does not have a valid fix.
To fix this problem we pad the "No GPS fix" sentence with spaces till it gets 31 characters long, which is and the max allowed by Digita.
There is an option not to pad the "No GPS fix" sentence, which is left from the original development stage of the emulator but will not be available in future releases or in the Photo GPS interface.
The emulator is written in Visual Basic 4 and (unfortunately) comes with a
lot of baggage.
There two versions to download. A full version with a size of 2.1 MB zipped and a light version which contains only the exe,richtext and mscomm controls.
If you have any other programs installed in your machine that are written in VB4 then download the light version. as the VB4 runtime is already installed, if you are not so lucky be...patient :-)
Click here to download the light version
Click here for the full version = 2.1 MB
Last updated : 04/05/2000