(Read 2 times)
May 03, 2012, 09:42 pm
Yes, but will the arduino run a DMD like that?
Location: Pittsburgh, PA, USA
I learn a bit every time I visit the forum.
May 04, 2012, 12:57 am
The Arduino chip can run the chips that can, even if it's chips on a shield on an Arduino.
SPI bus is (clock /
bits per second, IIRC. That takes 3 pins plus 1 pin for every control line. Some chips like shift registers, one control line does a whole line of them.
I find it harder to express logic in English than in Code.
Sometimes an example says more than many times as many words.
May 04, 2012, 07:15 am
Hi, I'm still going for the option of handmaking the DMD, how many shift registers can I use before the signal degrades, I would use rows of 4 down 128 across or vice versa (32 registers down, 16 across) will the signal degrade? I want to use a seperate arduino for the display, what is the smallest I can use. I would use a serial output from the main CPU to the DMD CPU which would use built in commands to detect, eg. It detects a three so it uses the assigned bitmap.
Will this work,
Location: Boston area, metrowest
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May 04, 2012, 08:15 am
I would use an octal register wired like a shift register,
use a part like sn74ac574 so you have good drive current, 24mA, not the measly 4-6mA of an HC595. That will drive the rows of anodes.
May need a buffer on the clock line, have to check the '574 input current requirements.
Then for the columns, shift registers driving MOSFETs to sink all the cathode current.
Size may be driven by the SRAM you need to hold the data array that you be shifting out.
Pinwise, need enough IO for Rx/Tx, SCK-MISO-MOSI, SS for columns and SS for rows.
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May 04, 2012, 09:36 am
Im not familiar with octal registers, are they larger versions of shift registers. I plan to use the chipKIT max32 to run the main machine, switches, bumpers etc. but a seperate controller for the DMD, I would prefer to use the chipKIT to run it as well, but if it simplifies it I would rather seperate. Will it be simpler?