Communication medium
Having recently acquired a military tripod which I plan to turn into a rocket launch pad, I wanted to experiment with the possibility of creating a wireless launch controller.
For this project safety is paramount, however I’ll the discussions around this to a later post. For now I wanted to experiment with different communication mediums and components.
I really want to be able to control the launch pad from my Android phone, without any extra hardware. That means the wireless options available to this project are:
GSM
Either communicating by SMS, GSM Serial or TCP/IP; the launch pad would need a paid SIM as well as sufficient signal (as would my phone). Most of the launch sites I fly from have good signal coverage however this is not my primary choice. I deemed this medium reasonably secure, as you’d need to know the number of the pad to hijack it – which is unlikely to be guessed. Additional encryption atop this is probably unnecessary. However, this implementation has many more “moving parts” than the alternatives so for now, it’s sidelined.
Bluetooth
The Bluetooth protocol is very well suited to this application, providing a simple, secure Serial channel over which to communicate. However, I struggled to find any cost effective units which had sufficient range for launching rockets (despite quoted module and protocol ranges). Perhaps they exist, I didn’t look very hard before moving on.
I did some experimentation with the HM-10 BLE module which I found to be excellent and can highly recommend. Just beware the myriad knockoffs which looks almost identical. These come with ancient, undocumented firmware which did sort of work, but there’s plenty of people having issues with them across the web and I failed to flash modern firmware to it.
WiFi
This is my current preferred medium and the one I’m pursuing. The pad can be configured to connect to a hotspot of my choosing using WPA2, so its extremely secure. Line of sight in a field should yield at least a hundred metres of connectivity.
I’ve been experimenting with the ESP-201 and the WEMOS D1 Mini Pro, both of which use the ESP-8266 chipset and feature IPX external antenna connections.
The ESP-201 is a bit more primitive than the D1 and I had trouble getting it set up and flashing it. Documentation is non existent except on a few other experimenters’ blogs, each of which give conflicting instructions as to what magic state to put each pin in for flashing.
So far I love the D1, its plug and play and hasn’t given me any issues. A range test is to follow with a variety of external antennae.
