dmd connector board

The Dot Matrix Display (DMD) is a 32x16 array of high-brightness LEDs for visually striking effects. [Product Page]
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i_demidov
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Joined: Sun Aug 21, 2016 2:19 pm

dmd connector board

Post by i_demidov » Sun Aug 21, 2016 3:29 pm

Where I can find the dmd connector board? I looked for him in shop, but haven't found. He goes complete with the display? I from Kazakhstan. Whether the dmd connector board will come here?

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stryker
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Re: dmd connector board

Post by stryker » Mon Aug 29, 2016 10:34 am

Hi, The DMD Connector Board (DMDCON) and a ribbon cable are included in the Dot Matrix Display package. I've not seen them sold as an individual part but anyone who has used multiple DMDs in a single display has spares. I don't know if Freetronics can ship to your country.

Brissieboy
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Re: dmd connector board

Post by Brissieboy » Tue Aug 30, 2016 5:29 am

You don't really need the DMDCON board. It does provide a convenient way to interconnect the cable supplied with a DMD to a Uno, but it does nothing other than provide those connections. You can simply cable the DMD to the Uno directly without using the board.
The latest version of the DMDCON also includes a pull-down resistor on the OE line which disables the DMD display while the OE is left floating (such as during power-up or reset). The latest version also has corrected the label on the 'OE' line which was incorrectly marked as 'nOE' on the earlier version.

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stryker
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Re: dmd connector board

Post by stryker » Tue Aug 30, 2016 6:58 am

Well spotted on the resistor - they've followed your lead Brissieboy. Will DMD2 library dim without it? I may have goofed removing your resistor in the latest versions of my boards is all...

Brissieboy
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Re: dmd connector board

Post by Brissieboy » Thu Sep 01, 2016 10:45 am

G'day Stryker,
That resistor is only useful when the OE line is not active (driven either high or low).
The only time this would normally occur is during powerup or a reset when the DMD has power applied but the Arduino has not yet had time to set the appropriate pin to an output. The Arduino pins start up in high impedance state.
The DMD will have some sort of random data in its latches and the OE line needs to be held low to prevent LEDs from lighting during this time.
All it does is prevent that flash of random LEDs on startup, and should have no effect on brightness control whatsoever. It is high enough resistance to prevent loading the line down, but low enough to pull the line low when it is not asserted.
It really should have been included as part of the DMD design.
And they also fixed the incorrect label of the 'nOE' to 'OE'. Great to see they do take notice. Thanks folks, great site!!

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stryker
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Re: dmd connector board

Post by stryker » Thu Sep 01, 2016 11:49 am

Thanks for the explanation. Based on that I'll restore a resistor there in my own boards in ongoing designs. I had removed it in the latest version which I intend to use DMD2, rather than your modded DMD library.

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