The completely open plotter

[AndersG]

OK. I have hinted at this elsewhere, ie to build a completely open plotter, hardware and software, suitable for use on a sailboat where power is limited. Attached are pictures of the current prototype, which draws under 300mA, including GPS module.

It is a daylight-viewable 7" touch-screen from NewHaven, connected to a Raspberry Pi 2, through an Adafruit TFTFriend and using an Adafruit touch controller (AR1100).

The TFTFriend has a maximum backlight current of 125mA and the display wants 180mA for maximum brightness. My idea is to create a PCB that plugs into the GPIO and has connectors for screen and touch as well as an USB keyboard emulator for frequently used fuctions. The PCB will have a backlight driver (FAN 5333x) capable of 180mA, with ambient light sensing, reducing the current to approx half in low-light conditions.

Sadly, there is quite a glare on the screen. Wonder if it is the resistive touch? It might also be a good idea to increase the contrast, possibly in software.