Saturday, 7 July 2012

Raspberry Pi week 1

Because of the need to run cables all over the lounge, plugging my Raspberry Pi into the antiquated telly is a bit of a bother still. So I have not fired it up again the last few evenings, first trick is to get a power supply. I want to be running it off a regulated boost supply from rechargeable batteries. This might prove all more difficult than it needs to be. I need another 30 quid in the budget, although a digital monitor would have made things move along a lot faster actually.

I have a 128x64 graphical LCD, which should give me 128/6=21 x 64/6=10 (21x10 characters) albeit super tiny using a 5x5 font. I have found a VT102 arduino app written using AVR libraries (not sketches) so it should be trivial to get a basic display using a serial terminal on the ttys0 :
This hack includes keyboard, which I do not want/need actually, will just have to reconfigure the keyboard to come from stdin I suspect. On second thoughts, the 5x5 font does not do upper and lowercase very well, which might be difficult to view, anyway I will have fun trying. Pictured below is a standard 8x5 font.
 (This display is available at Hobbytronics, and looks easier to drive and prettier than mine)

Portable power is still a problem, the boost regulator I have seems to have a design flaw, and the trimmer pot for ref voltage adjust has burned it's track and gone open-circuit at one end. Consequently the reg generates 14 volts from a 3.5v supply instead of the intended 5v. I get the impression I'll need a crowbar fuse. The shed in the back yard is a bit hot and time is limited tonight, so repair will have to wait, besides I need to modify the booster a bit since it's power-up surge is a bit too hungry. I'm still not set on what batteries to use either, nor on what solar charger setup I will use to top them up yet. I do know the charger will be having 3 solar panels, each about the size of my outspread hand though.

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