Will the Unicorn Hat work with Raspberry Pi A+


#1

I have been trying to get the Unicorn Hat to work on my Raspberry Pi A+'s, but no luck. I keep getting the error saying that the hardware is not supported.

Yet on the Unicorn spec sheet, it says it is supported.

Anyone out there have this same issue?


#2

It’s possible you could have a model of A+ that’s not in the list of supported devices for the rpi_ws281x library itself. The library deliberately works only with known versions/revisions of the Raspberry Pi to avoid any unexpected results.

You need to find your Pi’s revision ID by running: cat /proc/cpuinfo | grep Revision

If your revision ID isn’t listed here: https://github.com/jgarff/rpi_ws281x/blob/master/rpihw.c#L97-L119

Then raise an issue against the rpi_ws281x repo letting them know, or a PR including it.


#3

There are (at least) two versions of the A+, one with 256 meg of RAM and one with 512 megs of RAM. I have one of each. Both of mine have a Sense Hat on them. They are both also running Raspbian Jessie. Both are running headless and working just fine so I haven’t messed with upgrading them to Stretch.


#4

That definitely seems to be the problem. My A+ is revision 900021 which is not supported (yet).
I opened an issue, thank you for the suggestion.
https://github.com/jgarff/rpi_ws281x/issues/241


#5

Hopefully that will get merged in soon- then I can trickle it down to my distribution of rpi_ws281x and thus Unicorn HAT.

You can potentially modify the library yourself to get up and running in the interim. The rpi_2s281x distribution that Unicorn HAT uses can be found here:

You’ll need to:

git clone https://github.com/pimoroni/rpi_ws281x-python
cd rpi_ws281x-python
git submodule update --init

Then tweak library/lib/rpihw.c


#6

Thank you! Your suggest worked. The A+ format is a perfect size for my project. I’ll update the project area with a video of my progress. You guys are going to be blown away with what I have done. :)


#7

I have an A+ mated to my Sense Hat for the very same reason. Perfect size, its the same outline as the Sense hat. That Pi is running headless and I don’t need all the other ports etc. Looking forward to seeing what your up too.


#8

Here is my demo reel. 6 games so far, still working on a scrolling race game (huge!).

Let me know what you think.

:)


#9

Very nice. Very nicely done. That’s the 8x8 Unicorn hat right? I have the HD 16x16 on my wish list. My Sense Hat has an 8x8 LED matrix. So far I haven’t done anything other than display messages on it.


#10

Yes, I started my project with the 8x8 Unicorn before I knew of the 16x16 variant. The smaller format is very limiting, but I found that to be part of the fun challenge. How do you show the whole time? Scroll! How do you draw pacman? As a single yellow dot. Imagination fills in the rest. :)


#11

On my Sense Hat I display a scrolling message of day, date , time, temp, humidity, pressure, etc. Started with the text as all one color. Then set it up to change each element based on conditions, The temperature part shows in red for temps above 25c, blue it the temp is below 0c etc. My python file just keeps growing and growing lol. At some point I’m going to replace the Sense hat with the Unicorn HD and a BME680.