Unicorn Hat and Used Pins


#8

I’m very new, but have a question. This thread makes it sounds like I can run the Unicorn Hat via wires. Would I be able to run multiple Unicorn Hats from one Pi by connecting them all to the same pin on the Pi? Looking to have a little fun in my office at work! My coworkers have been spending hundreds of dollars on Hue lights. Unicorn Hat seems cooler!!!


#9

Yes, you could run multiple Unicorn Hats by connecting them all to the same pin.

I’m not sure exactly how many you could connect together before tricksy electrical mischief made the signal basically degrade into useless mush, but certainly a few!


#10

Ciao,

Have you had a chance to think about my question?
I’m still stuck to wiring the Unicorn HAT to the Pi…

Thanks!


#11

I have had success driving it from the following pins:

Pin 2: 5V
Pin 5: GND
Pin 6: GPIO 18

What I have not been able to do use only pi pin 6 for the data signal and use external 5V power for extra juice.


#12

You can do this, but you must have GND and GPIO 18 connected!


#13

Spot on. I grounded the external supply to the pi on pin 3, connected the 5V straight to pin 2 on the unicorn, pulled ground from pin 9 on the pi, and fed data from pin 12. Worked like a charm

The external power makes a huge difference when the brightness is at 1.0 and most of the display is lit up. Before when I was displaying white at full bright, it was more of a yellow, now it is very white.


#14

That looks good. Are you using semi-transparent white tape to diffuse the LEDs?


#15

I’m sorry to be such a bother but I’m still not able to make it work.

You used:

Pin 2: 5V
Pin 5: GND
Pin 6: GPIO 18

As far as I know Pin 2 is 5V (correct), Pin 5 is GPIO3 and Pin 6 is GND.
GPIO 18 is pin 12. Now I’m completely lost…

Can you take a picture of the Pi’s pin board and Unicorn Hat with the wires attached. I don’t need to use an external 5V for this particular project.

To test the result I’m using the preinstalled python examples. They work with the Unicorn Hat attached directly to the Pi.

Thanks once again…


#16

Ground should be pin 9. I’ll put together the circuit and take a pic right now.


Passthru pins on Unicorn HAT?
#17

Just some white paper taped to the board. Still looking for a more elegant solution, but this is saving my eyesight for the time being.


#18

Thanks! Now everything is clear!

Federico


#19

I also need to connect two unicorn hat. Which pins?


#20

Unicorn HAT only runs from Pin 18 using some highly specific signal generation code- the Pi is technically not capable of pushing this sort of signal out on any other pin. You can connect two to this pin, but they will display the same thing.

The normal way of connecting multiple devices with these kind of LEDs is to “daisy chain” them, one after the other. The trouble is, we’ve not provided an “OUT” on the Unicorn HAT so you can’t easily do this.


#21

I think that you have provided an “out” though. It doesn’t work with the unicorn hat library, but if you use the underlying ws2812 library to for your own custom “chain” of LEDs and the algorithms to support it, you should be able to use the breakout pins to drive as many unicorn hats or neopixel strands as you want. They will need to be externally powered though as the Pi can barely handle the unicorn hat itself.


#22

I’ve got my unicorn hat working well with wires coming off the GPIOs on the Pi into the headers on the hat… however I’d like to get a really low profile connection and solder wires direct to the hat. Can I use the VCC / DIN / GND for this and connect to 5v, GND and GPIO 18 on the Pi?


#23

I am guessing no given this: “make sure you plug them into the header and not the little breakout contacts on the side of the HAT though. Unicorn Hat has logic level conversion for the Pi onboard.”


#24

You can run it into the solder contacts on the Unicorn HAT, but it’s most definitely out of spec and could potentially damage your Pi.


#25

Since it’s not the best idea to soder to the 3 breakout contacts. What are they for??

My RPi isn’t arrived yet, but my Unicorn and the case. Any ideas how to connect the head and some other jumpers while the head is placed on the pi?

Like someone said, the Unicorn hat only uses GPIO 18. But why are the other ones connected too?


#26

if you are querying the full size header, the short answer would be that the HAT specifications require a 40-pin header, but regardless, most add-on will use a 40-pin header - as opposed to a shim - for the simple reason that it makes a secure anchor on top of the Pi and leaves little room for interpretation of how to connect it to it.

if you are querying the use of the 3 pin breakout on the side of the HAT, it is, technically, to daisy chain multiple sets of WS2812B,

In term of accessing the rest of the GPIO pins there are many ways to do that, more or less practical depending on what your project requires, from something like the Mini Black HAT Hacker, to accessing them from the bottom of the Pi or solder pads on the underside of the HAT, to even more involved hacks.

I suggest you create a new topic with any questions you may have when you receive your kit, and we can hep you fill the dots and clarify away from any satellite discussions that may be confusing matters more than helping.


#27