Has anyone tried having a single strip driven by two controllers (not at the same time)? Does it make sense to put diodes on the clock and data lines to prevent data (or rather, pulses) from one controller to ‘back-feed’ into the other?
It might - though I would think that the non-active controller would just ignore the activity on the line. Just make sure that you don’t have both controllers running at the same time.
(And dear gods, why would you want to do something like that?)
Working on a master-slave setup, where the slave is “local” to the strip and the master is some distance away. Normally the slave controls the strip, but if the master needs to take control, it tells the slave to stop sending data to the strip, allowing the master to then send data. The only other solution I can think of is to send data through the slave, but that just becomes cumbersome in the end. And particularly since I have no more IO pins available on the slave …
Yes I do need 2 controller to run 1 matrix because 1 use for text display and other for XYmatrix
@Nail_ENVY you realize that one controller’s led output will wipe the data from the other, right? You can’t use the 2 controller setup we’re talking about here to get overlay effects.
Yeah, I’m not trying to do what @Nail_ENVY is trying to do. Different setup.
Interesting setup - I think diodes should be enough (though, as a side question, will diodes interfere w/the data/clock rates you can get?). Also - make sure you’re using FastLED3.1 – I’m pretty sure I’ve adjusted all the SPI code for all the platforms on there so that it releases/disables the SPI hardware after writing out a frame (important for making sure your slave doesn’t suddenly believe that it is receiving SPI data 
Yeah that’s a test I’m going to have to perform … soon.
It is easy for me to get both @Aaron_Liddiment matrix control rolling text , and @Mark_Kriegsman XYmatrix together on the same display but not at the same time.
Love them both,so I put each on a separate controller.
I use a small 5vDC relay (control by the master) to switch the data and clock line.
Diodes allow charge to flow in one direction. This means you can transition from (say) LOW to HIGH through a diode. Once this charge passes the diode, it cannot pass in the reverse direction. Pulling the line LOW from the controller is done by connecting the line to ground through the controller. This will have no effect after the diode, because charge cannot be pulled through the diode in that direction, so as far as the LED strip can tell, it stays HIGH.
tl;dr: A diode won’t work.
@Luminous_Elements beat me to it (stupid typing on glass). While you can think of a diode as a one way valve, the clock and data are essentially AC waveforms.
You need a switch, be it electro mechanical, or silicon (or even more exotic) based.
… or none at all?
Just use a OR gate as long as you sending one at a time it will let you switch between the two
Hrm, interesting suggestion. That would be the simplest idea yet that I’ve come across. And you’re right, as long as both aren’t sending, it should work … Thanks!
A MUX should do the trick; didn’t look at the data sheet for this particular chip to see what timing looks like but it states that SPI signals will work.
I can’t do that. I don’t have any GPIO pins left to control a MUX, or anything else for that matter. The OR Gate idea should work …