strandtest failing for Rpi and DotStar LED strip

[danielharan]

I just got the DotStar LED strip (#2436, order 1555529-6079104889).

After cutting it to have only 40 LEDs on the strip and connecting it (a USB power supply, reads 4.99V), I tried to run strandtest.py, even though it's meant for colour. Tried again with 30 (changing the variable value in the script), same result.

No error is showing, and after a while the first 3 LEDs light up. I double checked that clock and data pins were correctly connected, added a ground from the strip to the Pi... still nothing. 5V and GND seem are making contact from start to end of the strip. Those 3 LEDs stay lit up and I have to disconnect power to reset them.

Is there anything else I should be checking? Is there an lower-level / easier way to get to "Hello World" with this than strandtest.py?

[adafruit_support_rick]

Are you using a level shifter on clock and data?

[danielharan]

I have no idea what those are. I'm just trying to run the basic strandtest.

led_strip_test.jpg (792.01 KiB) Viewed 355 times

[Arudinne]

I have no idea what those are. I'm just trying to run the basic strandtest.

led_strip_test.jpg

You need a level shifter to convert the RPi Signal to the higher voltage used by the Dotstar Strips.

Take a look at this guide: https://learn.adafruit.com/dotstar-pi-p ... star-strip

[danielharan]

Argh - I skipped over the section that's bolded but nested between a comparison with a product I didn't buy and right before code for the Arduino. I also ignored the 3.3V stuff at the end of the section on Rpi because I thought earlier models didn't have 5V, which the latest versions have (?) so it didn't seem relevant.

Anyways, I'm annoyed by this delay and hope you'll make the product description and docs clearer about what's needed to make this product work.

[adafruit_support_rick]

It's also pointed out here:
https://learn.adafruit.com/adafruit-dot ... tstar-leds

[danielharan]

Now that I bought a couple of those quad level-shifters, I'm wondering if there's a tutorial anywhere that shows a simple diagram of how they're supposed to be connected?

[Arudinne]

Now that I bought a couple of those quad level-shifters, I'm wondering if there's a tutorial anywhere that shows a simple diagram of how they're supposed to be connected?

https://learn.adafruit.com/dotstar-pi-p ... star-strip