Hi everyone,
Over the last couple of months I've read posts about using the MAX7221 to drive a matrix and may have even posted a question. It's been very useful, but there were still a few areas that tripped me up.
This is absolutely a matter of a beginner not joining the dots and getting to the bottom of the problems through trial and error has been for me, a very satisfying outcome.
Things I forgot, or missed in the documentation -
- Remember to make sure the pins driving the Max (CLK etc) are set to output mode;
- The max starts up, turned off. You need to explicitly enable the pins.
None of this is a surprise but with circuit diagrams looking like latin, I assumed that my initial problems were wiring related when in fact it was all down to software.
I've done a more complete write up with some basic, end-to-end code in the hope that it might benefit someone else later on.
Hope it helps, pictures are still outstanding (the first set were worse than useless) but any corrections on my understanding of things are very welcome.
Does anyone have any tips for wiring up the junctions? My soldering is at a similiarly basic level so a pre-built 4 position socket would be great (if lazy!)
Tips also for a frame would be good too - I've been thinking about coat hanger wire (or a similar grade of bulk wire) to form the matrix support but am open to suggestions.
Cheers
Thanks for creating a blog and posting it. It may save me a lot of research when I get around to adapting an 8x8 direct-drive array to more than that size.
Is there some way to print that complete article? Firefox's File>Print Preview and File>Print only get the first page. It's probably a Blogspot thing, but if anyone knows how to print the whole article in one go, I'd appreciate that tip.
Is there some way to print that complete article?
A rather over the top way is to install Firebug and edit the HTML of the page on the fly to get rid of the styling on one of the many, many DIVs being used.
I changed
<div id="main" class="main section">
to
<div id="main" class="xxx">
and it now prints fine.
Andrew
Thanks, Andrew. I'll look into Firebug, or maybe automate a way with Perl or Python from a saved HTML version of the page. This isn't the first time that print problem has happened to me. The code change for <div ...> is the magic incantation I was looking for.
P.S., I think that's originally your 8x8 direct LED driver I'm using at Arduino Playground - DirectDriveLEDMatrix, no?
Yep, that's mine, written with a complete disregard for current limiting resistors.
As for DIVs, I'm no CSS expert but I think it should be possible to create a web page that looks nice on screen and is still printable. Paper hasn't gone away yet - not until I get my A4 sized colour eBook reader anyway.
Andrew
Surprinsingly, IE 7 can print the page correctly (WYSIWYG), with no extra efforts.
It works perfectly well in Safari, also. Firefox will catch up, I'm sure.