Garmin GNS530
Version 1
The GPS was developed around the GNS530WAS software, supplied by RealityXP. This software used the GNS530 Trainer software supplied by Garmin, to provide an extremely accurate simulation of the real unit.
The first version was constructed using the LCD screen from a SONY PSOne add-on display and OpenCockpits interfaces. Initially hand-built dual concentric rotary encoders were employed, but these were later replaced with ELMA E37 units. The firmware for the OpenCockpits Encoder interface was modified so that it would work with the E37.
A VGA interface was added to the PSOne display, to improve the quality of the video output. Due to the vertical and horizontal timing requirements of the display, the 'Powerstrip' utility software application was installed to allow customisation of the graphics card video timing.
Version 2
The development second version comprised the replacement of the OpenCockpits interfaces with a PIC 18F4550 micro-controller development board and the replacement of the PSOne display. The replacement display was a 640x480dpi unit complete with a VGA interface, it was purchased from a Chinese website at a very reasonable price and was delivered to the UK within 10 days.
With the move from Microsoft Simulator FSX to Lockheed Martin Prepar3D, it was found that the RealityXP software was not compatible and that there was little support for the product and hence it was unlikely to be made compatible in the future. As an alternative the GNS530 software from MindStar Incorporated was installed and although this functioned with Prepar3D, it did not provide the full set of features available with the Garmin Trainer based RealityXP product.
Garmin GTN750
Due to the limitations of the Mindstar version of the GNS530, an alternative was sought.
In 2014 Flight1 released a Garmin GNS650/750 product for both Microsoft Flight Simulator and Lockheed Martin Prepar3D. Like the RealityXP GNS530, this product used the official Garmin Trainer software.
The main problem encountered during the development was to find a suitable display. The GTN750 display is 4.46inches wide by 5.27inches high with the diagonal size being 6.9inches, the resolution is 600 x 708 pixels.
It was not possible to the source a LCD display of the exact dimensions, so it was decided to use an oversize display but to make the front panel dimensions the correct size and then scale and position the displayed image so that it filled the front panel aperture.
A HJ080IA-1B/1E 1024x768 IPS LCD 8inch display complete with VGA was purchased from China at a cost of £73. The unit came complete with a resistive touch screen and interface, but unfortunately, due to the size constraints imposed by the front panel, this touch screen had to be replaced with something slightly smaller. A GPS tablet PC 171 x 132 mm 170 x 131 touch screen glass 8'' 4 wire resistive was purchased, again ordered directly from China at a cost of £7.
A micro-controller interface was added to connect the front panel buttons and rotary encoders. A low pin count PIC 18F14K50 was used, configured as a HID (Human Interface Device) joystick as the total requirement was only to interface 4 switches and 3 rotary encoders i.e. a total of 10 input channels.
Documentation
- gns530development.pdf
- GNS530 Version 1 Development
- garmingns530-version2.pdf
- GNS530 Version 2 Development
- garmingtn750gps.pdf
- GTN750 Development
