I wanted to preserve the usb capability of the ground module, as well as add bluetooth capability. I will start with this one, since it was the more straightforward module for me to put together. For the bluetooth module, I used an HC-05 that I had laying around from an earlier project. This module is very easy to integrate with the ground radio that I received. I began by first cutting off and desoldering the 6 pin header that was installed on the bluetooth module, and then cut the 4 wire cable that will be later used for the air module to get 4 short pieces of wire that I soldered up like so:
I then searched for the HM-TRP datasheet which is found here:
https://www.hoperf.de/upload/rf_app/HM-TRP.pdf to get the pinout for the RF module itself. We can intercept the UART data from here, as well as power. I soldered the wires previously soldered to the bluetooth module to the pads marked VCC DTX GND and DRX on this module with power and ground going to VCC and GND of course, and with TXD from the bluetooth module going to DRX on the Hope module, and RXD from the bluetooth module going to DTX on the Hope module as shown here:
That completes assembly of the ground module, so I just shrink tubed the bluetooth module by itself and then piggybacked the boards and used a larger piece of shrink tube to make a reasonably neat and compact package like so:
My intention is to use this module as a "relay" between the long range RF and short range bluetooth by plugging it into a small usb power source that are all over the place these days. Something like this:
The air module is a bit more involved and tricky, but still very doable. I forgot to mention that I added a very nice magnetic switch from Featherlight Altimeters:
https://shop.featherweightaltimeters.com/product.sc?productId=33&categoryId=2 to enable easy remote turn on and off when all of this is mounted in the rocket. I apologize that I didn't get pictures of a few of the steps I took making this up.
To begin this I took the 4 wire connector mentioned above and cut it to a length that would leave me adequate wire length but also not be excessive. I did not think to take a picture of this, but I'm thinking it was around an inch. I then cut the connector off of the gps module and stripped the 4 wires about 1/8" and tinned them. The pinout for the GPS module is described here:
https://www.aliexpress.com/item/HAKRC-Ublox-7-Chip-Core-OP-GPS-for-Openpilot-NAZE32-F3-Flight-Controller/32799709822.html?spm=a2g0s.9042311.0.0.hLQ1i2 , and the pinout of the connector for the air module wasn't marked on my PCB, but mine was RX,TX,VCC,GND, going from top to bottom of the connector with the antenna connector on your right side. I will try to show this with a picture:
. So now I took VCC and GND from the GPS and air module connector and soldered them together, along with the RX from the GPS to the TX from the air module and vice versa. This is then soldered to the pads marked OUT and GND on the Featherweight magnetic switch. Last is to install a battery connector to the magnetic switch and then heat shrinking the connections and the magnetic switch itself:
If you are not using the switch, then solder the battery connector directly to the power and ground wires soldered together between the air module and gps, or to your screw switch, or whatever you decide you want to do. At this point the soldering is all done and all I did from there was to piggyback the switch and air module together and again heatshrink them to each other:
That was all the construction for me.
At this point it's time to configure the radios and get them talking. I can add a screenshot later of my settings if needed, but from memory, I just changed the baud to 9 (9600), tx power to 20db, and mavlink to raw data and saved the settings. Then if everything went well, you will have screens looking like this:
and it should all be working.
Sorry for the formatting with the pictures. I'm not good with formatting forum posts.
