Thread: DIY digital compass: electronics experts needed!
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sarahn is offline sarahn
2009-09-28 , 00:46
Posts: 243 | Thanked: 172 times | Joined on Sep 2007 @ silicon valley
#32
Originally Posted by hopslink View Post
Seems quite reasonable. Take a look at the RN-41 BT module, it has a built in antenna and is cheaper at digikey. I haven't looked at the datasheet but they claim a 30mA power draw when transmitting, which is less than you have estimated: http://www.rovingnetworks.com/rn-41.php
I think meant to put down the rn-21 actually because physical integration looked easier. It still needs an external antenna according to the DS. I think I pulled 100mA off the datasheet somewhere but maybe it was the wrong one, thanks for pointing that out.


Originally Posted by hopslink View Post
While it may be slightly easier to prototype with complete modules like arduino you will have to start again when you move to your final design. If you use one of the common, low end microcontrollers from Microchip (PIC) or Atmel (AVR) you should find very cheap programmers and free development tools exist along with loads of example code for i2c and serial comms. HTH
The arduino has the same chip I picked out, the ATmega328. In fact given it's creative commons, starting with an arduino schematic and adding bluetooth / magnetometer to it may be the best solution.

The one thing which is different from board to proto is the bluetooth module, and I am unsure that is a big deal. In fact I think for prototyping it may be better to use what was used with the n900 push http://blogs.nokia.com/pushn900/wp-c..._guidev1.0.pdf

It is going to be in the sheet but not in the prototyping total.

I am going to update the original sheet. I would have used a smaller battery but there is nothing on sparkfun between 100mAh and 1100mAh right now.