nokia pcd8544 display - spi

by tldr on Sun Nov 18, 2012 11:38 pm

so there's this conflation of your furby teardown and a robobrrd bouncing around the void between my ears. what i hear in there crying to be released is a robobrrd chassis, with a pi brain, an adafruit 16 channel pwm controller to run four servos, (1 beak, 2 wings, and one to pan the eyes), and however many leds i can muster, and a pair of the nokia lcds for eyes. i've got the pi with festival running on it, so the brrd will be able to speak, the pwm controller arrived yesterday, the servos are in a box around here somewhere, and there are leds everywhere. sometime next week the nokia displays will get here, so i started looking at the arduino library and got to wondering why it doesn't use hardware spi. is it just to save the miso pin, since it's not used.

there are a couple of pcd8544 libraries out there for the pi, but they're based on your's and bit bang the spi. seems like on a chip that fast it would be nice to let the hardware go ahead and do it's spi thing so another process could steal a few cycles while the bits go dribbling out..

so i guess my question was, is there a compelling reason to not use hardware spi to drive this display?

also, since the datasheet says the chip can handle a 4Mb/sec data rate, it sounds like you could pick up the pace a bit on an arduino with an 8MHz spi clock.
"If I had known it was harmless, I would have killed it myself." - Phillip K. Dick, A Scanner Darkly
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Re: nokia pcd8544 display - spi

by tldr on Mon Nov 19, 2012 8:29 am

i guess on an arduino soft spi also frees a pwm pin and avoids any accidental invocation of slave mode.

may as well get out my thesaurus of obscenity and profanity and dive into python.
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