2019-08-18

Touch Screen

The Comvette system employs a GeeekPi 5 inch diagonal capacitive touch screen. Its native resolution is 800x480. The GeekPi capacitive touch screen responds to touch in the same way as your smart-phone. A light touch is all that is needed to trigger a response.

Note: I do not recommend using a "resistive" touch screen. Initially I used a 5" resistive touch screen from another manufacturer but I soon discovered that a resistive touch screen requires you to use a stylus or your fingernail when tapping on the screen. The soft pad of your fingertip doesn't register reliably with a resistive touch screen.

The GeekPi touch screen:

The GeekPi touch screen dimensions:

The Raspberry Pi must be configured to work with the touch screen. This is accomplished by adding the block of text items shown below to the Raspberry Pi's /boot/config.txt file.

# When using the GeeekPi 5 Inch 800x480 Capacitive Touch Screen HDMI
# Monitor the following settings must be used:
#
# framebuffer_width (console framebuffer width in pixels)
# framebuffer_height (console framebuffer height in pixels)
# hdmi_force_hotplug (HDMI output even if no HDMI monitor is detected)
# hdmi_group (DMT (Display Monitor Timings))
# hdmi_mode (custom video mode)
# hdmi_cvt (custom CVT Coordinated Video Timings)
#
framebuffer_width=800
framebuffer_height=480
hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=87
hdmi_cvt=800 480 60 6 0 0 0

The touch screen is attached to the Raspberry Pi with a standard HDMI cable. The HDMI cable carries video from the Raspberry Pi to the touch screen. The touch screen receives power (5 volts) from the Raspberry Pi via a USB cable. The touch sreen also sends touch screen events back to the Raspberry Pi via the USB cable.

Note: Because the Raspberry Pi has very little power to spare I recommend that you plug the USB cable into a powered USB hub attached to the Raspberry Pi and *not* into the Raspberry Pi itself.

A Wiki is available that describes the touch screen in more detail. It can be found here.