Tuesday 28 May 2019

MEGAphone screen testing

Just a quick post about recent testing of the interface for the screen on the MEGAphone rev1 PCB.  

First, we knew once the PCBs had been ordered that the screen connector was in the wrong place, and will have to be shifted sideways.  Then a bit further exploration revealed we had the display enable line tied low instead of high, which had been causing the display to remain blank. With that fixed (seethe thin blue wires near the screen connector), and a bit of the usual jiggery-pokery, we finally had an image on the screen:

 We then also found that the viewing angle of these particular screens is all wrong for us: It expects the screen to be used upside-down.  When viewed from the wrong angle it is quite dim, and there is blurring and doubling of the image, as the various anti-glare and polarisation filters are all misaligned from that perspective, as the following images show.

However, as the MEGAphone and MEGA65 have no frame buffer, we can't just easily invert the image.  So we are looking for another supplier of compatible screens.  This is not too hard, as these 800x480 4.3" screens are a dime a dozen, and are manufactured by a whole bunch of Chinese companies.  We are talking with a supplier now about one that not only claims full 180 degree viewing angle, but also 2x brightness. This will be very welcome.

Just for fun, we also enabled the on-screen-keyboard to see how it looks. We might still need to darken the background behind the keyboard (it is composited over the top of the regular display) a bit more.  I'll make a video of this when we get a bit further, as the animation of it appearing looks quite nice already. I also hooked up one of the buttons so that pressing the button automatically makes the keyboard appear or disappear: No software cooperation required!

Anyway, that's it for now. I did say it would be a short one :)

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