FEZ Hydra

Hi Guys,

I have just received a FEZ Hydra and I am looking forward to using it. I have a couple of questions.

  1. l notice on the PCB that the RTCLK crystal is missing, is this correct? The board version is 1.2.

  2. I cannot find a definitive answer to what voltage the uC runs on I think it is 3.3v, the schematic shows VCC and +5v.

Thanks for any help.


Not sure about (1), but I think the RTC was left off to keep cost down. All gadgeteer mainboards make both 5V and 3.3V available to each socket, so it is not one or the other, but both. Pin 1 = 5V, Pin2 = 3.3V on every socket. You’ll notice that on the DP power module, for instance, the recommended power input minimum is 6V, 1A. This is to make sure there is adequate power available to the mainboard.

[edit] - the mainboard itself uses the voltages Gus mentions below.

  1. This is optional since most users do nto need it. See pictures here please http://www.ghielectronics.com/catalog/product/328

  2. It is 3.3V and 1.2V but why asking? As this is a .NET Gadgeteer mainboard, you should be using the power module (the red module) to power up hydra. Please see product description above. Of course if you have electronics background then you can make your own “power module”.

Welcome to the community.


Thanks for the reply. I do have an electronics background thats why I asked the question because the uC power supply requirements are missing on the schematic, only showing VCC to the power connections to the uC, and making a guess in this environment is not an option. Currently I cannot source the power supply they appear to be out of stock in the UK. I am really looking forward to using the Hydra, I currently have the FEZ Panda II (for about a week) and slowly getting to grips with C#. Thanks for what appears to be a great product.


Gus if one wanted to enable the RTC on the Hydra, what’s involved? Other than installing a crystal, where would one connect the battery. I assume there are no base classes for RTC on the Hydra.

Good but I have to be careful not give the wrong answer to software people. We do not want to see smoke coming out of a new board :slight_smile:
I suggest you read the gadgeteer design guides by Microsoft and the (partially complete) ebook we have to understand more on the gadgeteer concept. For example, every single gadgeteer maiboard MUST accept and require 3.3V and 5V, which si what the red module provides.

Get any standard 32.768Khz crystal. That is it. You of course need a battery but note that VBAT pin on hydra is 1.2V max.


This would be a 1.2v button cell connected to VBAT and GND on connector 1, looking at the schematic.
Or any 1.2v battery.


it is 1.2v, up to you where it comes from

They’re part of SparkFun’s Crystal Kit http://www.sparkfun.com/products/9994 which is always nice to have laying around :slight_smile:

Just wondering if the “specs” of the crystal are important in this case. This is what’s in the Sparkfun package:

Does that sound about right?

Those are very common and I doubt you will find common one that wouldn’t work.

The one you pointed out is fine.