I am working with a single discrete NeoPixel, which doesn't seem to be sold directly by Adafruit any more, but this still seemed like the best place to post. I got my NeoPixels from https://www.digikey.com/en/products/det ... 58/6134706.
I have a board design that is fairly basic. It has an RF module, SMA antenna connector, a single NeoPixel, and a 40-pin female socket header mounted on the back side. The purpose of the socket header is to be able to mate the board directly onto a Raspberry Pi, like this:
A ground plane fills the board on top and bottom.
The design looks like this:
Here's my problem: The NeoPixel only updates when I am touching the tip of a multimeter probe to the net of the NeoPixel's Din pin. The other end of the probe doesn't need to be connected to anything. Touching the Din net with a different wire doesn't help. Additionally, I can touch the Din net at the Din pin on the NeoPixel, at the header pin on top of the board, or at the corresponding header pin on the bottom of the RPi. Same behavior in all cases. This is very weird to me because I am pretty sure that the issue isn't just a bad connection. Some things I've tried:
- - two separate boards, one with the RF components and one without; same issue on both.
- resoldering the NeoPixel connections on one of the boards twice.
One thing that DOES work: If I remove my board from the RPi so that it is no longer mated directly to it, and I run jumper wires between the two, the NeoPixel works fine.
Any ideas here? I am at a bit of a loss, and any thoughts would be greatly appreciated. Thanks!