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WS2801 with Rasberr Pi 3b+
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WS2801 with Rasberr Pi 3b+

by jucofan on Thu Nov 21, 2019 4:35 pm

I am working on a Christmas light project that I have done for the last few years. In my first iteration of the project, I used 1 stand of the RGB WS2801 LEDs. I drove them through SPI from my rPi 3b+, and simply wired my +5v to a standalone power supply, and tied my grounds together (power supply, pi, and LEDs). My LED strand worked with the code, and everything was great. After the Christmas season, I disassembled and boxed everything up.

Last year, I followed my written instructions, and replicated the project. Everything worked, except for the LEDs. Only the first 4 would light, and only the first one of those four would behave properly. After dozens of times checking code and wiring, I couldn't find anything wrong or different from the previous year (other than raspbian updates that I had performed). I figured I had a bad LED strip. So, I bought another one, only to find that this one is behaving the same way. I don't know what is wrong or different than before.

I am using Python3 to call my file, which was probably written in Python2. All of my digital outputs and sequencing are working with no problems at all. It's just the SPI won't behave.

I have the 6V power supply running only the LED strand (have also tried a 5V supply). My 5V supply was capable of providing 2 amps, a nd the 6V supply is rated at 0.75 A. I had the same experience with both supplied I am using pin 6 on the Pi as a common ground. I have also tried numerous ground configurations.

My Data connection is MOSI on pin 19 and SCLK is Pin 23. I have verified numerous times, and even tried reversing them. I am pretty confident my wiring is correct, because the first LED on the strand acts as it should. The next three light up, but only one of those changes colors, although not as it should. Beyond light #4, nothing happens.

What could be going wrong with my setup? My code has not changed, but I'm reading a ton about having to have occidentalis installed, but it has since been depricated. Was there an update to Raspbian that removed or changed the functionality of SPI?

I've tried downloading a few of the libraries associated with the WS2801 lights, but I have not had any success. All of the research and tutorials from Adafruit all lead me back to a depricated solution.

jucofan
 
Posts: 2
Joined: Thu Nov 21, 2019 3:21 pm

Re: WS2801 with Rasberr Pi 3b+

by jucofan on Thu Nov 21, 2019 5:35 pm

Update - I looked at the wiring diagram on the Adafruit tutorial a dozen times, but never picked up on the fact that I should be SUPPLYING power to the 5VDC pin (pin#2), so I removed my USB supply and tied my 5VDC in such that my power supply (switched back to the 2A 5VDC supply) is now powering the Pi through pin 2 AND the LED strip. And, not noticeable difference.

FWIW, I can feel the non-illuminating LEDs, and they are as warm as the ones that are illuminating, which makes me think the chips are getting power, but makes me wonder about the pulse train being sent down the line...

jucofan
 
Posts: 2
Joined: Thu Nov 21, 2019 3:21 pm

Please be positive and constructive with your questions and comments.