If you have an APM (or compatible) flight controller, and Telemetry set, chances are, you’ve hooked it to your smart phone. You need a special USB cable, called usb OTG cable. It convinces your phone’s usb controller to read other peripherals. But cables break, right? Well, mine did… I couldn’t bother fixing it, so I did something better! Ardu Pilot Mega Telemetry-Wifi bridge with ESP8266… it reads APM’s telemetry, and forwards it to ESP8266. ESP creates a Wifi access point, you can connect to, so Tower app can bind to that IP, and control the craft. It’s basically a wireless USB cable 🙂
What we need (Parts List)
ESP8266 (I have ESP01) with NodeMCU,
Telemetry module (preferably air module-without usb),
0.9V-5V to 5V DC-DC Booster Module
1 cell LiPO battery charger,
1 cell LiPo (mine has 650mah-lasts for hours)
3.3v voltage regulator- LM1117 3v3 0.5A should do
a case (I used 2xAA battery case)
booster, ESP, telemetry module, charger with battery
Prepare the ESP8266
Flash the ESP with NodeMCU, I use Terminal, but it can also be done with NodeMCU flasher in Windows. Then use Esplorer, to upload the program, or sketch for Arduino folk 🙂
Esplorer to upload Sketches
On the right pane, select your serial adaptor, 9600 baud and click 
. If you can’t see the adapter, click the 
button. After connecting, if you see the “Can’t autodetect firmware, because proper answer not received.” error, don’t worry, it’s because ESP has initialised before you connected to it. Just click 
on the right, or reset the ESP.
Once you are connectred to it, you need to upload the program to forward data from telemetry to wifi. Download Init.lua.zip and unzip it (I do not claim credit for that init.lua, as it was downloaded from the internet, sadly I forgot where I found it. If you know, drop a comment, I will give credit). In Esplorer, the left pane, Open the init.lua, and it should show the contents in the panel. You can change the AccessPoint name and password. To upload it to ESP, click on 
. That’s it for the ESP, set it aside for now.
Prepare the enclosure
As I said, I used 2xAA battery case from christmas LED lights. I think the price for that was about 2eur, and it also has a switch :). Chop off the LED strip.
Battery enclosure without LEDs
Open it, remove every bit of plastic, except the switch retainers.
Unnecessary plastic removed, left some around the switch
Charger and Booster
For this step, we need the LiPo charger, 3.3v to 5v booster and a LiPo battery. If you use air Telemetry module without the USB connector, you can hack the 5v booster. Just chop off the connector, it makes it a lot smaller. Be careful and leave the four tiny through-holes.
5v booster hack
For the charger, I had the ides to put it at the bottom and also see the status lights. I removed the smd LEDs, and soldered an RGB led. I used common ground led. You can leave it as is.
Hacked LiPo charger with rgb LED
Solder the three together. Battery to Charger, charger to booster, switch between charger and booster.
Battery circuit, soldered
Crude schematic of battery circuit
Connecting everything together
The telemetry also works on 3.3v but the module has its own voltage regulator, and I didn’t want to hack the module. We need another 3.3v voltage regulator to power the ESP8266, so we stick it between booster 5v and ESP8266. It’s also smart to use a capacitor on the regulator output line, something around 10uF should be ok. Also connect Telemetry TX to ESP Rx, and Telemetry RX to ESP Tx.
Final schematics
DO NOT POWER ON WITHOUT ANTENNA, OR YOU MAY DAMAGE THE TELEMETRY!
Put it in a box
I placed the battery circuit on the bottom, placed a slab of veroboard on top, on which I glued/soldered ESP and Telemetry.
Circuit-in-a-box
Be sure to make holes for usb and led. I used my soldering iron to melt the plastics, be creative 🙂
USB and LED openings
LM1117 3v3 voltage regulator is soldered on the bottom of veroboard with some other connections, just to make thing nice (notice the tiny smd capacitor between Gnd and 3v3).
LM1117 3.3 on the bottom
Connect like in the schematics in the picture and hot-glue everything together. Notice the hole for telemetry antenna on the left.
Telemetry and ESP on the top
I wanted to see the smd led through to top, so i poked some holes with my trusty iron tip again.
Holes on the top for SMD leds
Configuring the Tower app
With your smart phone, find the APM Telemetry wifi, and connect to it. Name and password are in the init.lua. Change to whatever you wish. Open the Tower app, and go to Settings
Tower app settings
Change Telemetry Connection Type to TCP
Open USB, TCP and UDP settings, and make it look like that
USB, TCP and UDP settings
That’s it. Click Connect and you should be ready to go… or fly…
Tower Connection successfull
Hi Sirs,
I read this one carefuly, but I don’t understand some matter:
1/ Did you using Telemetry Usb (Ground) connect with phone via OTG cable ?
2/ How to the APM transfer signal with esp ? I don’t see wiring from Telem (apm) to esp.
hello
)
No, there is NO cable from the phone. Phone connects to ESP via WIFI. I broke my OTG cable, faster to build something than buying new cable 🙂
Signal, I don’t know, this bridge/box is usually besides me.
wifi-esp connection is on one of the pictures (
I understand pictures sometimes don’t show, please refresh page.
OH, I think maybe you understood this wrong
Drone has telemetry module, sends telemetry out over air. There is NO ESP on the drone.
My bridge box reads telemetry from drone with telemetry module, relays it to ESP. ESP sends telemetry out wia WIFI. Telemetry and ESP are on the same board.
Phone connects to ESP via wifi, reads telemtry.
Nice solution, well done.
I only have a pair of radios at hand. ie an airborne module and a USB module.
Do you know how I can utilise the USB module in your setup?
Thank you 🙂
Yes, if you have serial to usb converter, you could connect the USB telem to serial converter, and the rest should be the same.
I did actually started making a PNP module just for that, but never quite finished it…
I can whip up the schematics, if you want to try it yourself 🙂
Great idea, thanks. I do have a couple of ftdi converters here so that is an option. I will breadboard it up today and see how it goes.
I like your PnP option too. Is that a usbotg cable to the radio module?
I think that would be a great final solution for me.
great 🙂 The small USB connector is to program the ESP chip, the big one is for the usb telemetry.
I have also looked at the data sheet for the FT232RL chip on the radio module and I could tap into pins 1 and 5 which are the tx/rx inputs and then continue on as above.
nice. Let me know if it works 🙂
Hi. By default, wifi works on the first channel. My friend has the same bridge, when used nearby we will interfere with each other. How to change the wifi work channel? Thank you.
Hi
you can set WIFI.AP channel in cfg table: wifi.ap.config(cfg)
Here is the link to the NodeMCU docs (https://nodemcu.readthedocs.io/en/master/en/modules/wifi/#wifiap-module).
I guess you can scan the air at the beginning to find an empty channel, and set it to that.
Might be doable.
Thanks for reading 🙂