Table of Contents
Radio modems are used to transmit the current position, battery voltage and similar properties to the ground. The PX4 autopilot can be flown without in manual mode, but for setup and advanced features a telemetry link is absolutely necessary.
433 MHz Antennas
The antennas here fit all 433 MHz radios. Some might need adapters (e.g. 3DR's odd choice of RP-SMA for the connector requires an adapter).
Diamond SRH771 1/2 wavelength monopole
A great monopole for usage on the ground:
This small and light antenna is great for onboard usage.
433 MHz / 868 MHz / 900 MHz Long Range / Outdoor
3DR USB Radio
Firmware Upgrade Reference for Developers (Mac OS)
brew install sdcc # in case there is a link error, you can resolve it by issuing: # brew link --force xdcc
compile the firmware
git clone https://github.com/tridge/SiK.git cd SiK/Firmware make install
upload it to the radio (adjust the serial port name):
tools/uploader.py --port /dev/tty.usbserial-CHANGETHIS dst/radio~hm_trp.ihx
Note: The red led first blinks, then becomes solid during programming. After the successful reboot the green led should come on (blinking if the 2nd radio of the pair is off, solid if they are in sync).
AT Commands / Set the net ID
Connect to the radio modem serial port with these settings:
* 57600 baud rate * No parity * 8 data bits * 1 stop bit
On a *nix system screen does the job:
screen /dev/tty.usbserial-CHANGEME 57600 8N1
Then start command mode:
DO NOT TYPE ANYTHING ONE SECOND BEFORE AND AFTER
List the current settings:
Then set the net ID, write settings and reboot radio:
ATS3=55 AT&W ATZ
You might have to power-cycle the radio to connect it to the 2nd radio
jDrones Long-Range Telemetry Set
jDrones offers long-range RFD sets as fully ready made, Plug-N-Play sets for Pixhawk and other users. Modules have all power filtering, level and USB adapter eg. everything needed to connect them to your vehicle. Their firmware is optimized for MAVLink communications and low-latency telemetry use.
These long-range modems are based RFDesign modules and offers easily over 5km ranges with normal antennas without dropping signal.
There are two versions available:
The RFDesign RFD900 is protocol- and firmware-compatible with the 3DR Radio, but offers substantially greater range. You can mix and match the two (e.g. a 3DR Radio on the vehicle and an RFD900 at the base station) as well.
2.4 GHz 3DR WiFi telemetry
The 3DR WiFi telemetry module is running a Lua-based firmware, NodeMCU, and three .lua files stored in the module memory. init.lua, config.lua, setup.lua
Change the module configuration
Download the ESPlorer program, follow the instruction on the website to install it and then run it.
To run it on Linux type:
java -jar ESPlorer.jar
- Connect your module by USB, set baud rate to 9600 and click open.
- Under NodeMCU+MicorPython select the tab Snippets, and Edit the Snippet0 to Config with the command advancedconfig and click Run.
- Download the configuration file: config and extract it.
- In the tab Scripts open the early downloaded file config.lua.
- Set your desired SSID and password.
- Click save to ESP.
Restart the module, you should now be able to connect with the module with your new SSID and password.
2.4 GHz Short Range / Indoor / Vicon
For indoor or short range setups, the use of the Lairdtech PRM123 module is recommended for control channels, since its very reliable and has a low latency. The Roving Networks WiFly modules are recommended for sending back the telemetry data, as its bandwidth is very high and multiple modules can be easily set up with one Wifi Router.
All modules listed below use the XBee pinout. These adapters can be used to connect them onboard or offboard via USB:
- OFFBOARD (computer)
- XBee Explorer USB Dongle (SparkFun Store)
- Onboard socket: Play-Zone
Roving Networks WiFly UART to WIFI bridge
The Roving Networks WiFly modules deliver up to 1 MBit/s (921600 baud) of UART to UDP or TCP/IP bandwidth. The range is limited (as with any Wifi device), but the modules are very helpful for high-bandwidth tests if a lot of telemetry data has to be pushed through the link.
- Recommended module: RN-XV WiFly Module (SparkFun Store)
Digi XBee Proprietary
Wiring these modules to the adapter is standard and straightforward:
- Pixhawk 5V ↔ Module 5V (make sure to use a regulated adapter!)
- Pixhawk RX ↔ Module TX
- Pixhawk TX ↔ Module RX
- Pixhawk RTS ↔ Module CTS
- Pixhawk CTS ↔ Module RTS
- Pixhawk GND ↔ Module GND
NOTE: Leave RTS and CTS unconnected if the module does not support hardware flow control or its disabled (if it does support it, connecting them is highly recommended). The standard Pixhawk pinout is on this page: Pixhawk Autopilot.
WIFI Access Points
The PIXHAWK and sFly ETH projects have tested a wide range of access points (including multiple models from Linksys, Cisco, Netgear and D-Link. The most reliable model and the one with the best range is the D-Link DIR-825.
Rock-solid ASUS router with great reviews. Extra long antennas:
D-Link DIR-825, Wireless Router, DualBand 300Mbit/s, Gigabit
This model is rock-solid and well-proven even in outdoor setups at -15 deg. Celsius.
An example for a ground station / radio tripod can be found here.