3.3V and 5V How to use on the Spark Core


I have a question witch i cant find an answer on anywhere so i have to make this question.

As i can see the Spark Core is running on 3.3V DC.
Or can it also run on 5V as the Arduino ? When supporting the board without the USB power. On the GND and VCC connections.

Does that mean the I/O ports then only provides 3.3 V when they are set to High ?
And what about 5 V DC on input ports, will that damage it

Because now i use Arduino witch components requiring 5V, will that not be possible on the Spark Core ?

Or will i then need to have a 5V to 3.3V DC Converter to power the Spark Core and the normal components requiring 5V ?

Hi @Centauri,

You are correct that the Spark Core runs at 3.3V. However there are a number of ways to work with a 5V circuit.

The Shield Shield will convert between 3.3V and 5V, so you should be able to use any 5V Arduino shield with the Spark Core.

Most of the pins are 5V tolerant, with the exception of the analog pins (A0 to A7) and D2 which are only 3.3V tolerant. This information is documented on the Spark Core github page, and will be further documented (more clearly) when our new documentation page is published.

The Spark Core is also intended to run off of 5V power, which it regulates down to 3.3V. This is how it is powered off of USB, which is 5V. If you connect your 5V power source to the RAW pin, it will be regulated down to 3.3V, and the VCC pin will be a 3.3V output.

Hope that helps!

EDIT: I forgot about D2 when I first wrote this post, so edited this post to be correct.

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I’m looking to buy some Spark Cores, but I’m having some difficulties understanding how to power the Spark Core itself and other items in the circuit.

Most of those items require 5V, but I can’t even seem to find a battery setup providing 5V. And do I then hook up these distance sensors, potentiometers, LEDs, … directly to my power on a breadboard, or does the power come from the Spark Core (or should these I/O items only be connected to the Spark Core via their switch pin to manage “user input”)? Something like parallel vs in series. Can I fry the device when connecting something the wrong way?

I haven’t even begin to think about amperage and whatnot. And these are just a few of the questions I have. Just trying to grasp the basics and hoping I’m ordering the right stuff.


I have another question on powering the spark.

Let’s say I have a power supply connected on the RAW pin. Will it kill the spark when I also connect a USB cable? ( You can’t do this with Arduino right?)

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@Quagh The Spark Core will comfortably take up to 6V, so a few AA batteries should do the trick if you’re looking for a simple battery set-up. Otherwise you can get our Battery Shield, which’ll provide power from a LiPo battery. In fact, since the Spark Core can be powered over USB, the easiest way to handle battery power is using an off-the-shelf USB battery pack (the same one that you’d use for a micro USB phone).

There are always many ways to implement your sensors and actuators, but generally speaking a good place to start is by powering them from the 3.3V and the 3.3V• pins on the Spark Core. 3.3V will provide a regulated 3.3V whereas 3.3V• provides a separate filtered 3.3V specifically for analog sensors. If they need higher voltages than 3.3V, though, you could power them directly from your power source rather than from the Core.

The Spark Core can be fried (specifically the on-board voltage regulator) if it’s provided voltage higher than 6V, but it has protection against high current draw, so it should be resilient to shorts. However power is always the best way to accidentally break your Core, which is why we recommend providing power over USB, at least to start.


@Joris if you power the Spark Core over RAW and also attach a USB cable, it should be fine; the circuit has a protective diode to protect any upstream devices (like your computer or power supply providing power over USB).

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Specifically this information is documented on the GitHub under pin mapping: https://github.com/spark/core/tree/master/Pin%20mapping

I really wish the SparkCore had an official “datasheet” of sorts where all the information was in one centralized place. I guess if the github was a little easier to navigate that would work.

Hi, trying to hookup a barcode scanner to to the spark core. I just took a look at the schematic on github and it looks like +5v on the USB cable is connected directly to VIN. As the ps2 scanner requires 5v does that mean I can safely use VIN as a +5v supply for the scanner if my project is powered from microUSB?

Many thanks.

Yep that should work. The only possible concern is if it draws a ton of current, but I don’t think that would be a problem

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Excellent, thanks for the ridiculously quick reply, I was planning on using a spare iPad mini charger (5V @ 1A). IIRC the scanner draws 275ma so there should be more than enough current available for both at full load.

Thanks again!


Im about to buy this GPS module https://www.sparkfun.com/products/11571
It seems it also requires 5V I was thinking if this module can be connected to TX/TR and VIN pins for 5V power source… [UPDATE: it seems it uses 3.3v so thats great]

Hi @cjnewbs , I needed to increase the voltage to 5V for the step motor and I came to this piece that help me test it.

This should work, its a really easy step up.


That’s a nice step up converter but it’s only rated for 120mA output. The Core consumes up to 300mA max (however I don’t know if that’s considering loads on all of the I/O or not).

What kind of amperage could I get to the core without shorting it out. I want to hook up a 5v/2amp power suppy to a breadboard to power some gas sensors and the Spark Core. Would that be too much over the VIN?


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@hubertron, the “power” goes to both the Core AND your sensors. That way, the Core consumes what it needs and so do the sensors. You are not using the Core’s onboard regulator. :smile:

It was my understanding that on the VIN it went through the Sparks voltage regulator to step it down to 3.3 v. Is that not the case?

Yes but are you powering the sensors with 5V or 3.3V?

I’m about to use the Spark core in a project where the RX/TX will connect directly to the TX/RX of a 5V Atmega. I could not, from the Spark documentaton, get a sense of whether the Spark RX pin is 5V tolerant. In one part of the docs it says pretty much all the pins except the analog ins and D2 can handle 5V, in another part it lists out only D0,1,3,4,5,6,7.

I actually had to go to the Spark schematic (https://github.com/spark/core/blob/master/PDFs/core-schematic-v1.pdf) to see which STM32 pin is used for RX (PA3) and then to the ST datasheet (http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00161566.pdf) to look up the pin and see that it is indeed NOT a 5V tolerant pin.

Well, at least Spark is open and I can easily work this out!

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So does the shield shield convert everything so that the spark core is protected from over-volting?

Or is it only the power into through the power supply, and not the power into the pins?


It’s is protected by the Logic Level Converter IC used on the shield shield but always good not to have overvoltage conditions :slight_smile: