Greetings all,
I am in the process of incorporating a Neopixel LED strip into my project and for appearance purposes, I would prefer not to have the controller constantly attached to the strip. Is it feasible to pre-program a gradient of colors, say from red to green, upload it to the strip, disconnect the controller, and have the colors saved on the strip with only power still connected? Appreciate the clarification.
Regards,
Peter
Does the Neopixel have memory?
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- adafruit_support_bill
- Posts: 88093
- Joined: Sat Feb 07, 2009 10:11 am
Re: Does the Neopixel have memory?
As long as power is connected, they should retain their current state. All memory will be lost when the power goes away.
One concern is the potential for noise on the unconnected signal line. Since the Neopixel protocol is a one-wire protocol, it is possible for it to mistake noise on that line for pixel commands and end up with some random behavior. If it becomes a problem, a weak (100K should do) pulldown resistor on the signal line should prevent that.
One concern is the potential for noise on the unconnected signal line. Since the Neopixel protocol is a one-wire protocol, it is possible for it to mistake noise on that line for pixel commands and end up with some random behavior. If it becomes a problem, a weak (100K should do) pulldown resistor on the signal line should prevent that.
- jps2000
- Posts: 811
- Joined: Fri Jun 02, 2017 4:12 pm
Re: Does the Neopixel have memory?
I would suggest a CMOS bidirectional switch at the input ( Like a 4053) to have the input grounded when the controller is off.
The out of the switch goes to the neopixel. The NC in of the switch goes to GND, the NO goes to the controller. The switch is supplied by neopixel supply and needs a >100k resistor in the control line to the controller.
This avoids the controller to be back powered via ESD diodes in off. This problem you have anyway when switching just the controller off an leave the neopixel on power.
You can control the switch via a hardware logic such that 2 pins of the controller operate the switch that one pin needs to be H and the other needs to be L. This avoids that during reset when all pins goes H the switch goes on.
Concluding: It is tricky but should work.
The out of the switch goes to the neopixel. The NC in of the switch goes to GND, the NO goes to the controller. The switch is supplied by neopixel supply and needs a >100k resistor in the control line to the controller.
This avoids the controller to be back powered via ESD diodes in off. This problem you have anyway when switching just the controller off an leave the neopixel on power.
You can control the switch via a hardware logic such that 2 pins of the controller operate the switch that one pin needs to be H and the other needs to be L. This avoids that during reset when all pins goes H the switch goes on.
Concluding: It is tricky but should work.
Please be positive and constructive with your questions and comments.