DMD2 and EtherTen

The Dot Matrix Display (DMD) is a 32x16 array of high-brightness LEDs for visually striking effects. [Product Page]
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eggman
Posts: 4
Joined: Thu Jan 07, 2016 4:48 am

DMD2 and EtherTen

Post by eggman » Wed Dec 18, 2019 4:35 am

Hi, I am trying to get a Freetronics EtherTen to work with a DMD display using the DMD2 library. Obviously there are issues with shared SPI pins. I note that the usage of SoftDMD permits non standard pins to be specified. However the question is which other pins are suitable to use? I have seen a number of other threads referring to similar scenarios. However nobody seems to be doing exactly what I am doing. Any assistance on the specific alternate pinout would be greatly appreciated. Many thanks.

Brissieboy
Posts: 190
Joined: Fri Sep 20, 2013 7:25 am

Re: DMD2 and EtherTen

Post by Brissieboy » Wed Dec 18, 2019 7:04 am

Once you sort out sharing the SPI, you should be able to use any available digital pin that is free for the others by using:
SoftDMD(byte panelsWide, byte panelsHigh, byte pin_noe, byte pin_a, byte pin_b, byte pin_sck, byte pin_clk, byte pin_r_data)
I don't think you have any choice with the SPI pins. They will be hard-wired on the board in any case.
I suspect you may have trouble with interrupts taking the focus away from what you are trying to do. The 'ether' part will probably generate an interrupt when it needs attention and this could occur when you are in the middle of a DMD update causing corruption.
I haven't used the EtherTen so can't be more help than that, but it does appear that others have been successful using DMD (not DMD2) on EtherTen here.
Best way is to give it a go - the more you experiment, the more you learn.

eggman
Posts: 4
Joined: Thu Jan 07, 2016 4:48 am

Re: DMD2 and EtherTen

Post by eggman » Tue Dec 24, 2019 1:18 am

Thanks Brissieboy. I have successfully used the DMD library with the Etherten previously. The problem arises when you dim the display. That is when the flickering is noticable as I gather the PWM that is responsible for the dimming function is in conflict with the Ethernet activity. I was hoping that by using the SoftDMD pin assignments I could remove any interrupt conflicts.

However I gather from your response is that the conflict is on the SPI pins which cannot be changed. And therefore a pointless exercise.

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