I haven't updated this thread in a long time, but my son and I continue to plod along iterating and updating our telemetry flight computer project. My plan has always been to open source this for students and hobbyists, but no matter how much progress we make, it always seems like it is in a massive state of work in progress and it keeps getting more complex -- defeating our original "cheap and easy" intent. Eventually, we'll reach a point where we can take a snapshot and share a version.
As a recap... we have a flight computer that is based on an dual-core ESP32, running Arduino code, that integrates a GPS, IMU, 200G accelerometer, barometer, SD logging, and transmits (bi-directionally) to a handheld base using high power serial radios. It has other bells and whistles, like hall sensors to detect fore/aft separation and remotely turns on/off cameras. At this point, we are just using it for flight data, event data, and tracking, but the next step is to also use it for staging and firing events.
Originally, we had a handheld Arduino with a TFT display and serial radio, acting as the base station. This served us well -- with a pretty common code base between the rocket and the base, but in the last year we decided to port the base application to an iPad mini to vastly improve the tracking, weight, and overall experience. Surprisingly, creating the app on the iPad (using iOS Swift) turned out to be much easier and far more powerful than we thought. We interface the iPad to the serial radio/modem using a Redpark serial cable and we mount the whole thing on a pistol-grip plate with a Yagi antenna. We've tested it to 14 miles line of sight and flown it dozens of times. Using the iPad gave us native access to the device GPS, magnetometer, maps, voice synthesizer, and dozens of other bells and whistles that you can't get using an Arduino and LCD display. But... at a cost of the iPad mini and the $100/year developer fee to Apple, so not the low cost option.
That said, the new version on the iPad has been amazing and fun to work with. It has been simple to add things like spoken warnings if the rocket is descending directly overhead or spoken warnings if the descent air speed is too fast (e.g., no drogue). We get to see all the telemetry data live, including the direction bearing and horizon angle, and distance, along with the speed. Additional screens on the iPad show the rocket location(s) on a satellite map, allow us to send the rocket commands, see radio streaming data, view log files real-time, etc.
This project for us has gone way beyond our original "quick and easy" for students, but my lesson learned is that if I had to do it again from scratch I would have used an iPad or Android tablet (or phone) to as the base station. There is so much power and capability in the device and very little incremental effort, once you master how to code "hello world" in the device IDE.
We are going to keep iterating and improving it, but in the meantime, here are some photos:
Here is where we started - the old base station:
Here is the current rocket board in a 3" package (board, radio, battery, GPS):
Here is the new iPad "base station":
screen shots:
And here is a quick one minute video overview of the base station screens: