Now, a problem with the system is that the display controller (MAX7219 must run on ~5V) and the ANT+ module (nRF24AP2) is at ~3V.
To over come the differences a level converter was employed (http://www.freetronics.com/products/logic-level-converter-module).
Worked like a charm.
Now, we still have a problem in that our LiPo batteries aren't going to give 5V (even 4.2V at full charge wasn't enough to get the display updating properly).
Prototype one (without ANT+) used a boost converter to get to 5V from a single battery however the battery ran out after about 3.5 hours on the road.
As we need more power capacity and increased voltage I just added another identical battery in series and a 5V regulator (https://www.sparkfun.com/products/107).
This gives me a 5V source for the display subsystem and the Arduino Pro Mini 3v3 has its own 3V regulator.
The level converter is then put between the 3V Arduino SPI signals and the 5V display.
To over come the differences a level converter was employed (http://www.freetronics.com/products/logic-level-converter-module).
Worked like a charm.
Now, we still have a problem in that our LiPo batteries aren't going to give 5V (even 4.2V at full charge wasn't enough to get the display updating properly).
Prototype one (without ANT+) used a boost converter to get to 5V from a single battery however the battery ran out after about 3.5 hours on the road.
As we need more power capacity and increased voltage I just added another identical battery in series and a 5V regulator (https://www.sparkfun.com/products/107).
This gives me a 5V source for the display subsystem and the Arduino Pro Mini 3v3 has its own 3V regulator.
The level converter is then put between the 3V Arduino SPI signals and the 5V display.
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