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Author Topic: Scrolling LED matrix display - Parola for Arduino  (Read 48239 times)
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Thanks !
Any specific reason you see 10 as a limit?
No reason, I actually mis-counted the modules in the video  smiley

Thanks!
Geoff
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The web site has been updated with an additional PDF file documenting the hardware BoM, component sources, and assembly of the PCB.
https://parola.codeplex.com
« Last Edit: November 22, 2013, 09:11:19 pm by marco_c » Logged

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Great job on the PDF Marco
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Marco,

I have just completed populating eight of your boards and would just like to compliment you on your well written assembly documentation
+1 Buddha points from me  smiley-cool

Pedro
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That's top feedback Pedro.  It did look very comprehensive.  I've ordered my components - going to tack 20 of these boards onto my next Seeed order  smiley

Geoff
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You will not be disappointed Geoff. I only have eight going at the moment but four more would be good. I am  currently looking at the code examples to work out how to only use combinations of some of the functions. Great library.
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Marco wanted to say thanks again.  I've made up 20 of these and the result is lovely, and still plenty bright enough even powered from an Arduino.  My intent is to make this into a self-contained display with an ATMega embedded in it.  I have a small bug to work out yet - the 16th module from the left (regardless how I shuffle the modules) has several horizontal lines displayed.  I'll do some more investigation on that.

Cheers ! Geoff
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Thanks. I also got lines sometimes and what fixed mine was powering down the display (remove the connector) and then back on again, followed by an Arduino reset.  To me it seems there is some timing issue on the reset at the start, as it appears to happen more frequently when many modules are used.
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hmm mine is more of a constant.  There is always 4 lines on the 16th module regardless which module I swap in there and tonight I've swapped them around a few times to confirm.  I have seen the effects you mention though, on other parts of the display especially if I hit reset when an animation is in progress.  Hopefully I'll get some time to look into it more closely this week.
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I have received a few private emails about this project and it is good to see that others are able to use the information to do their own thing. Of interest may be the following from one of the emails as it relates to some hardware behaviour noted in earlier posts:

Quote
I didn’t change any of your parts or circuitry, but I did add an adapter board with 3 x 10K resistors on it. They go between DI, CLK and CS to ground. When the Arduino starts up or I reset it, the matrix doesn’t flash up briefly before displaying.
 
One thing I have noticed is that some modules show junk at start up (and it never goes away). If I rearrange the modules (reposition the module that shows junk) they all still work. Just a case of finding a position it works at. I suspect it’s the 7219’s that might be getting through the QA check a little too fast...
 

If anyone finds the solution to the 'junk' being displayed, please let us all know...
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If anyone finds the solution to the 'junk' being displayed, please let us all know...
Hi, Mine is solidly always the module 16th from the left, and always the same pattern.  Has anyone in your PM conversations tried 20?

It's not a major issue as I'm thinking 20 is probably a bit too long to make a mount for and I'm likely to break it into two horizontal rows of 10.  But it's a puzzle!
Geoff
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Same person that gave the feedback above was running 20 of them.
Correction: 20 were made but the display is only 10 modules.

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I ordered some Parola PCB’s from SeeedStudio, got the parts and LED 8x8’s and built up 20 boards. Built them up like Lego’s and they worked first time.

I must say yours is a weird one, being in the same position irrespective of which module it is. If you PM me I can put you in touch with the other 20 board pioneer smiley

« Last Edit: August 14, 2013, 12:14:07 am by marco_c » Logged

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I'm one of the guys with 20 modules that has been doing a lot of testing trying to see what works to get the artifacts off the Parola displays. And I'm posting to say that I was pretty much convinced if the display suffers from that, I was stuck with it. However after a lot of hours of "tweaking", I have a work around that I use.

To start with, after doing everything from building tri-state buffers (to inhibit the signals from a cold boot), triggers to clean up the wave forms, pull-down resistors, and generally mucking around in the MDMAX library, and using my scope to make sure all was well, I found that if I disconnected the Vcc after the Arduino booted up (I'm using a MEGA 2560), then reconnected Vcc and do a soft reset on the Arduino, the crud was gone. Every time. If you try this you'll probably find that once running even when you disconnect Vcc, the displays will stay on. Something isn't right there and I believe that's a "clone" chip problem.

I also found that I needed to add 10+ modules before any artifacts ever showed any way. The artifacts were also random. The best way to force them to appear, power down the Arduino and power it back up within a few seconds. If I let it sit for a few minutes and powered it, I got "luckier" and had less artifacts. Sometimes this lead me to believe I'd found the magic cure. Nope.

So in programmer speak I came up with YAWA based on how I noticed the displays did work. Yet another work around.

What I did was built a power adaptor board where I can cold boot the Arduino, and in the setup() I can enable a pin to turn on the Parola power (after which I delay 1 second to let the chips fall where they may). Hence, when I power up the Arduino, if there are any artifacts on the displays, a warm reset will clear them every time.

The power adaptor uses a 2N3904 to drive a P-Channel MOSFET. It's not designed for high speed switching on and off but it works on my 20 modules every time. Sort of a digital "magic wipe"...smiley

In my project I'm only using 10 of the modules (it's a birthday present for my brother). There's a DS3231 RTC, a Bluetooth HC-04 (connected to Serial1). The project is controlled by any Bluetooth terminal so I can toggle between clock and scrolling message, any changes are stored in EEPROM for a reboot. On the inside from left to right you can see my power board, MEGA with proto-shield; RTC and Bluetooth, and buck converter to take 9-12VDC and knock it down to 7V to feed the Arduino's power jack.

Mel


* PowerBoard.png (22.58 KB, 641x436 - viewed 149 times.)

* Roly_Front.png (205.08 KB, 640x176 - viewed 157 times.)

* Roly_Inside.png (249.64 KB, 640x164 - viewed 165 times.)
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Nice one Mel,

I really do like the wood-grain case.  I'll give your idea of cycling the power manually on my 20-array tonight.  If that works I have some logic-level MOSFETs somewhere so will make up a standalone board with the ATMega and MOSFET to drive that.

Thanks for sharing your experiences,
Geoff
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Nice one Mel,

I really do like the wood-grain case.  I'll give your idea of cycling the power manually on my 20-array tonight.  If that works I have some logic-level MOSFETs somewhere so will make up a standalone board with the ATMega and MOSFET to drive that.

Thanks for sharing your experiences,
Geoff

I just put together a second 10 module unit tonight and it works with the power adaptor board as well. Curious to see how yours works out Geoff and if that mod does help with the artifacts. To save you time wiring the board thing up, you can simply disconnect Vcc at the Parola, give it second or two, plug it back in, then do a soft reset on the Arduino. That should work as well.

Mel
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