Flight Computer Prototype Component List

• SparkFun Arduino Mega Pro
• Falcom GPS
• RF Monolithics DNT900 Radio
• SparkFun Power Shield
• SparkFun 2000mAh LiPo Battery
• DS18B20 Temperature Sensor

I started using a battery to power the flight computer and radio.  The SparkFun Power Shield and LiPo battery work very well to provide power for both.  I chose the 2000 mAh battery because the radio may transmit up to 1 watt requiring 1.2 amps for a brief instant.  Additionally, I use some of their sample code to read the battery voltage, and transmit it along with the GPS data.

To improve the data throughput performance, I increased the baud rate of the GPS to 19200 from 9600, and similarly for the radio to 19200 from 9600.  I modify the GPS in the flight computer program because it requires a battery to persist a baud rate different from the default.  Also, if the flight computer detects errors from the GPS, I can reset the GPS and baud rate.  Lastly, the GPS presents multiple NMEA sentences by default.  I reduced them to just two that provide relevant information similar to what an APRS packet contains.  This also improved performance a little.

While I was looking forward to planning battery life tests and communication distance tests, I thought I would add temperature sensors.  I added two Maxim DS18B20 sensors.  With the microlan and single pull up, I thought these were easy to install.  Also, there is sample code available in many places which helped me evaluate them quickly.  After some optimizations to the code, I’ll be ready to begin some tests.