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Author Topic: Semi-newbie needs direct drive 8X8 matrix help  (Read 647 times)
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Help with 8X8 matrix please ...
Moving from the realm of Arduino beginner to Arduino intermediate, I'm using and Auduino Uno and am now trying to code and hook-up a mini 8X8 direct drive red led matrix from:  http://www.interactionlab.biz/v2/?p=176 .  This code won't compile correctly at this point:

for (int i = 1; i <= 8; i++) {digitalWrite(cols[i - 1], LOW);

I know that the trouble is with:  i &lt;=8    Should it be rewritten as:  i <= 8 

Also, since my Jameco 8X8 led matrix came without indicating which pin is #1, I'm trying to discover which is pin #1 by using this note from the same web page:

"Best way to figure out rows and columns is to get a pen and paper, put your multimeter on the diode check setting, and start touching pins. Once you get one LED lit up, know that your positive meter lead is on a row, and your negative is on a column.  Keeping the positive lead in place, move the negative lead in order to find the other columns."

I'm assuming that I can perform this operation without connecting the matrix to the Uno by holding the positive lead of my multimeter on any matrix pin and then touching the negative lead to any other matrix pin ... but nothing ever lights up.  What am I doing wrong?
Thanking you in advance for your help. - arduinodude97209 - 
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This may help, I did something similar:

http://www.gammon.com.au/forum/?id=11516

Quote
I know that the trouble is with:  i &lt;=8    Should it be rewritten as:  i <= 8 

Yes. That's HTML for less than.

Quote
I'm assuming that I can perform this operation without connecting the matrix to the Uno by holding the positive lead of my multimeter on any matrix pin and then touching the negative lead to any other matrix pin ... but nothing ever lights up.

What mode is your meter on? You probably need ohms mode so it puts out a voltage. Also try reversing. If you have the lead the wrong way (for a particular pin) it will never light up.
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