Cube:Bit with Raspberry Pi - no blinkenlights


#1

I bought the 5x5x5 Cube:Bit kit, along with a Zero to drive it with. Unfortunately there seems to be very little documentation on the Pimoroni site as to how to get it working. But since it uses Neopixels, I figured I could use the Adafruit libraries to get things going.

The TL;DR version of the story is that I couldn’t get any of the LEDs to light. Initially I thought I was using the wrong GPIO pin, but on closer inspection is appears the PWM pin used to drive the chain doesn’t actually go where it needs to. I was able to use hookup cables to drive the array via the GVS headers, but not on the RasPi headers. So, in the end I put a jumper between the BCM18 on the Pi header, and the DIN pin on the GVS header, and it works…


#2

On closer inspection, the pin on the Pi header seems to disappear off to the Micro:Bit header, then possibly over to the small transistor shown below:


#3

However, the board on the product page looks like this:

image

Have I got an old (or maybe new) version of the board? I don’t really want to keep a jumper cable attached, and even a bodge wire is going to look pretty crap. Although the cube itself is pretty cool…

Any ideas? Sorry for multiple posts, but apparently I’m only allowed to put one image in a post.


#4

Hi,
The BCM18 pin (pin 12) is connected to the equivalent pin on the Microbit header and then passed through the level shifter FET so it works with >5V power supplies. This level shifter is new to version 1.0 of the base board - the image on the web site is of an earlier version.

Exactly what power supply are you using into the base? I will try to re-create the same scenario

Gareth (4tronix)


#5

Tested with a 1A USB power supply (labelled Raspberry Pi), a RPi Zero WH and the purpleRain code from https://4tronix.co.uk/blog/?p=1827 using version 1.0 base. All works fine. So I suspect either there is something wrong with your base or the power supply, hence the question which supply are you using?

Gareth (4tronix)


#6

I’m using a 2.5A Raspberry PI (Element 14) USB PSU. Bought from Pimoroni.

It seems to work fine with the jumper wire installed…


#7

Hi,
That’s actually rather strange. It was exactly this power supply that led us to incorporating the FET level shifter as it kicks out more than 5.2V. We’ve since found other, high current, PSUs generally stick out >5.2V when unde rlight load. This can cause the neopixels to misinterpret the 3.3V command signals. Hence the level shifter to make these command signals up to 5V. I think we need to get your base unit changed as something must be wrong with the (trivial) level shifter. I’d love to find out why, but would need it back here to do that.

I’ll sort it out with Pimoroni

Gareth (4tronix)


#8

Cool, I’ll drop them a line.


#9

Hey all,

We’ll get a replacement base out for marria01 and have sent on our freepost address for the return, @4tronix please let us know if you’d like it sending on to you once we have it, cheers.

Matt


#10

yes, please do that
Gareth