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RPi + Other Software [Help] APA102 not receiving signal.

Discussion in 'Hardware Support' started by Brandon Horsley, 22 May 2018.

  1. Brandon Horsley

    Brandon Horsley New Member

    I will post code when I get home from work.

    I have 150 (I will only need like 100 of them) apa102 LEDs hooked up through a logic voltage converter chip using an 5V 8A power supply on the high side and 3.3v from my rPi 3 on the low side. Here is the chip:


    As a note I have also hooked things up without said chip and I get the same issue. There is no difference.

    Ground for said chip is connected to both the rpi and the negative voltage on the power supply. Pin 19 is going to the left most input, and the output is going to DI. Pin 23 is going to the right most input, and its output is going to CI. I have double and triple checked which pins I am using.

    Observations: When one of the data cables (i forget if it is c or d) is disconnected, the LEDS cascade to white. If ground is unplugged, they randomly shuffle colors. power supply is 5.65V, but my rpi's 5v pin is outputting at 6.3V for some reason. At no point have I ever seen a cascade of Hypercon starting up, a color select from hypercon's color preview, or a direct call of hyperion giving it an output value. I have run an spi test found here:


    It comes back as shown when pin 21 is connected to 19, and comes back as all zeros when pin 21 is disconnected. I do not have an O-scope yet, but I will be getting my hands on one soon to view the signal coming from pins 19 and 23. Using a DMM, I have measured 5.6V on the 5V side of the LED strip, and 0V on the ground side, relative to the rpi's ground.

    Software: I freshly reinstalled raspbian, initiated SSH and SPI, and then ran hypercon from my laptop, installing hyperion over ssh. Hypercon config is stock values using apa102 at spidev 0.0 and 0.1, and varied bitrates from 50k to 8MHz. Config file successfuly saves and sends, and the SSH log shows a proper config file initated whenever hyperion is started up. I have tried uninstalling and reinstalling my OS and hyperion.

    Thoughts: There might be a library I need but don't know about, since I did not run any git pulls like I saw in previous builds. I also previously used a WS8201 using the PWM, and almost got it working, but it was still shuffling colors and being a real pain, so I just waited for my 5v and apa102 to show up in the mail before reinstalling a fresh raspbian, and retrying with the apa102s.
  2. Akriss

    Akriss Active Member

    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    I have much better results using a level shifter from the 74HCT family. I use mostly use a 74AHCT125.
    Some reference reading: (https://happyinmotion.com/?p=1247).

    Hope it's of help