Added a small GPS (GP-735 https://www.sparkfun.com/products/13670 ) to the project, and used TinyGPS to decode the NMEA sentence. I played around a long time trying to get the gps commands to turn on and off different settings. Finally ended up using UBlox U-center software to send the commands separately, while listening to them with a Saleae Logic analyzer to help with the formatting. It is set to change the baud rate from the default 9600 to 115,200, and turns off every sentence except for GPGGA. This sentence gives Lat/Lon and altitude. That way the Teensy won't be trying to do too much, since I am making it read from the 9DOF and pressure sensor 100 times per second, as well as doing the orientation math, and sending all the results to the ground station over the radio modem. The GPS outputs data at 10 hertz.

Modified the ground station RocketNXP.pde to accept the lat/lon and display it on the screen and modified the log file to record that data as well. The data file is now named with a date and time stamp for the file name. A new one is created each time RocketNXP is started.

I ran across a few very cool products that I wanted to share. One is the MPU9250 9DOF sensor that is made to be soldered onto the back of a Teensy. Yes, this is small folks! It includes a MS5637 pressure sensor on board, because he had so much extra space left.

But what is very intriguing to me is his Ultimate Sensor Fusion Solution board. It uses the SENtral chip to take all the processing load off the Teensy. Unfortunately, this does not come in a form factor that plugs into existing pins, and must be wired.

I have tried the GPS on the freeway, and at 10 hertz it gives position updates at about every 8 feet (70mph). Sometimes readings to not update every 100ms, and can repeat previous readings one or two times before updating. The readings are time stamped by the .pde program, but the timing of them does not quite make sense. I need to do some more testing, and plan to use GPS time in the XBee data to help sort the issue out. Perhaps the program is doing something that interrupts the update of the GPS lat lon. However, the other sensors are getting their 10ms updates consistently.

After I sort this issue out, it's on to graphing altitude, etc.