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OlduinoChristmas Card (SD Card and LCD)

December 26, 2013

Once the SD card was working combining it with the LCD was dead easy. You can see the result on youtube: 

The olduino is reading a bitmap file from the SD card and writing it to the LCD – easy peasy.

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In the first picture you see the membership card at the top, the olduino below that, and the shield adapter below that. The shield adapter and the olduino sit on the 30 pin MC connector. You can see an extra set of 8 headers at the left end of the 30 pin set – these bring up the N lines and /MRD from the MC. The shield adapter is only talking to the 1802, it doesn’t use any of the olduino components and would work without it if you loaded the code into the MC some other way.

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In the second picture you see the rest of the hardware stack. The SD card shield on top mounts on the shield adapter with the two sets of 8 and 6 pin headers at the right. The protoboard, bottom right mounts to the same headers passing through the SD card shield, in the middle bottom is a little adapter that just converts the Olduino’s 5 volts to 3.3 for the LCD and, off to the left is the LCD meant for a Nokia 5110 cellphone. These LCDs are cheap and easy to find. They display 84 pixels across by 48 down.

In the next few you can see the whole stack assembled and the bitmap displayed on the LCD.

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The bitmap by the way was done with something called lcdAssistant(http://en.radzio.dxp.pl/bitmap_converter/) that takes a windows bitmap and converts it for use with popular LCDs. That’s really the whole point of the Olduino for me, being able to use hardware and software developed for the arduino community with the 1802.

I haven’t measured the transfer speed but it should be 20,000 bytes per second because the read loop is 5 instructions. The reality is it takes around a tenth of a second to read a 512 byte sector or write the 504 bytes to the lcd. I’ll have to look into why.

If anybody has some better low res graphics from pixie days, I’d be interested. I’ve also been thinking maybe I could do a grey scale display by alternating display of two bit maps on the LCD: I’d get 3 values depending on whether a pixel was on in one, both, or neither of the bitmaps. For a static image I could probably do 3 bit maps for 4 levels of intensity without seeing a flicker.

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