Low cost high quality DMX multi-chain interface for RPi

[Phil Smith]

This is a picture of the pi with proto hat whilst testing.

[richbass]

exciting!

[Phil Smith]

Oh is that how you're supposed to do it! I'm embarrassed by my effort now..

[richbass]

Oh is that how you're supposed to do it! I'm embarrassed by my effort now..

Its not been tested yet
Looking neat is one thing, but actually doing what its supposed to is something altogether different!

And if it wasn’t for the hard work of others I would never have known how to do it at all.

[liebetim]

Hi all,

I'm attempting to build one of these myself, following the instructions others have described above. Unfortunately so far I've been unable to output to my lights. I've attached an image of my setup and the datasheet for the IC I'm using. The list below is everything I've tried/checked so far. Hopefully someone else sees the missing piece that I'm overlooking!

• Triple checked all wiring
• Disabled bluetooth output per Massimo's instructions
• Checked pin voltages:
  • Pin 4: 4.83V
  • Pin 8: 0.01V
  • Pin 12: 4.82v
  • Pin 16: 4.80V
• Used a second MC348N
• Swapped the +/- outputs (blue and yellow wires)
• Tried multiple cap values, and using no cap at all
• Ensured universe 1 output is set to UART

At this point, I'm not sure what else to try. I'm hoping there is a simple mistake that I'm missing. Any help would be appreciated!

Thanks,
Tim

[GGGss]

Without a scope or a DMX tester, you cannot judge if the DMX timing is respected so your fixtures will accept the DMX payload...
I can't see problems with your circuitry, except for the fact that you have all 4 blocks working, which is unnecessary. You can only use 1 of the 4 blocks.
I don't understand why the capacitance is between V+ and gnd. It will short-circuit high frequency voltage ripples.

[liebetim]

Without a scope or a DMX tester, you cannot judge if the DMX timing is respected so your fixtures will accept the DMX payload...
I can't see problems with your circuitry, except for the fact that you have all 4 blocks working, which is unnecessary. You can only use 1 of the 4 blocks.
I don't understand why the capacitance is between V+ and gnd. It will short-circuit high frequency voltage ripples.

I appreciate you taking a look. I had initially wired it up with only one block and without the capacitor, but when it didn't work I figured I'd copy Phil's layout to a T. I may try some more experimenting. I'll post my solution here if I get it to work, otherwise I'll probably just pick up a USB adapter.

-Tim

[liebetim]

Turns out it was just a bad SD card. I clued into the issue when I kept having to re-flash the image after rebooting. Bought a new SD card and everything worked like a charm. I did also have to disable Bluetooth to utilize the UART pin.

I attached some pictures of my build along with the vero layout I came up with. I've also uploaded the files for the case to Thingiverse in case anyone would like to use the design.

Thanks to all!

-Tim