Phoenix connector polarity


Hi everyone,

I’m probably missing something, but in the datasheet for the balenFin, I can’t find any reference as to the polarity of the phoenix-connector. On the PCB there seems to be a small minus-character to the right side of the connector, but I’m not sure enough that it refers to the connector to take the plunge and risk blowing up my Fin. Can anyone tell me what the correct polarity is?



Hi @martenjacobs the positive terminal is the one with the square pad, nearest the barrel jack. We’ve improved this in newer PCB revisions by marking both the + and - on the PCB to make it clearer, and we also mention in the getting started guide that the negative is denoted by the - symbol, but it doesn’t hurt to check. I hope this helps!


Hey Chris,

Two suggestions:

  1. Add that comment to the datasheet as well.

  2. Add a similar comment in both places clarifying that the DC barrel jack is center pin positive. AFAIK there is no standard for these things, merely industry-specific conventions. Musical instrument peripherals seem to use center pin negative, for instance.


@jschon thanks for the suggestions - always welcome!

Here’s a photo of the silkscreen on our latest revision :slight_smile:



Awesome. :slight_smile:


Hi I just received my first Balena Fin V1.1 as a Kit I was expecting to see the Phoenix connector in the kit but its not there so I looked on your site under accessories and its not there either ?

Can you tell me how I order this part please?



Hi Alan,

The phoenix connector is soldered to the board (the one between the barrel jack and the micro-usb).



Thanks, I’m talking about the green 15 way connector that is shown in the images for the kit?


Alan, you can find the “phoenix ring” variant of the case in our store.



Hi Nicolas, I see that you can use the mini PCI express slot for extra storage what storage can I use ??

The Mini PCI express port on the Fin expands the connectivity capabilities to a number of different modules (4G LTE, Zigbee, LoRa, additional storage, RS232/485, CANbus). The 4-pin USB header allows a wide set of possible design applications such as additional storage, secondary ethernet port, multimedia readers, additional radio interfaces, etc. The co-processor 18-pin header allows analog and time-sensitive I/O

Also is there another serial port on the 18pin header and if so do you have a descriptive pinout document?