As I mentioned in my first post about HC-12 433MHz radio modules, I’ve put my interest in them for telemetry purposes. While S.Port telemetry I’m using in FrSky Taranis radio might have higher range than HC-12, it is closed environment. Since $10 for a pair of HC-12 is not much, I’ve decided for more open DIY solution.
Setup on a quadcopter consist of one HC-12 configured for FU3 mode and baud rate 9600bps connected to SPRacingF3 UART3 port and “air cooled” (shortened with a coil) 433MHz whip antenna. Well, to be precise, it’s 450MHz since I changed working frequency. Antenna is not tuned or scientifically computed. Just 433MHz version shortened a little using proportions. Antenna is mounted on GPS mast. In next version I will probably replace whip antenna with Vee antenna.
Continue reading HC-12 433MHz RF serial module range test
HC-12 are cheap 433MHz wireless serial port communication modules with a range up to 1800m in open space. They are SI4463 based. Each costs about $5 when bought from China, and 2 of them can create wireless UART link that can be used, for example, to transfer telemetry data from UAV. Or drive IoT device. Or connect sensors. Or whatever else one can think of.
It is based on SI4463 RF chip, has built in microcontroller, can be configured using AT commands and allows to use an external antenna. Working frequency is divided into 100 channels starting from 433,4MHz up to 473,0MHz with 400kHz channel separation. Maximum output power is 100mW (20dBm) and receiver sensitivity differs from -117dBm to -100dBm, depending on transmission speed. It accepts 3,2V-5,5V power supply and can be used with 3.3V and 5V UART voltage devices (5V safe). Continue reading HC-12 433MHz wireless serial communication module configuration
Some time ago I have written a tutorial how to setup Bluetooth based telemetry link between Cleanflight and PC or smartphone. It's simple and it works. But it has some disadvantages. For example, connection is very very slow and has a limited range: up to 10 meters. While it is enough to change PIDs before flight or plan a mission with EZ-GUI, it is not enough to have a real, usable and reliable, telemetry link.
Luckily, Bluetooth is not the only cheap radio protocol we can use for purposes like this. Why not to use WiFi? Since market saw ESP8266 some time ago, cheap programmable WiFi modules became a reality. There are cheap, they are simple to use and can be programmed to do much more than just act as Access Point or network client. There are many alternative firmwares. For example ones that provides transparent bridges via TCP to allow pass serial ports over WiFi. Almost like serial over Bluetooth, but using WiFi instead. In theory that gives more range, higher speed and lower delay. Why not to use it to connect Android smartphone to drone flight controller and have nice an cheap telemetry solution? Exactly, why not. In this example how to do it with Android EZ-GUI and Flip32 running Cleanflight 1.12, but exactly the same trick can be used for Betaflight, SPracingF3, iNav, Baseflight, Naze32, APM, Pixhawx, MultiWii. If anything is using UART, it can also use ESP8266 as serial bridge over WiFi. Continue reading WiFi telemetry for Cleanflight with EZ-GUI and ESP8266
With their latest transmitters and receivers FrSky changed telemetry protocol. XJT module, Taranis radios, X8R, X4R and X4RSB are using SmartPort telemetry protocol. And that creates few problems. First of all, SmartPort is a serial protocol. That means, flight controller has to have free serial port to connect S.Port device. Second of all, TX and RX lines shares the same wire. The work in half-duplex mode. Third of all, SmartPort signal levels are inverted: logical 0 is in HIGH state, logical 1 is in high state. All of that combined, connecting SmartPort receiver to flight controller and sending telemetry data is not so easy to archive. Specially on FCs without hardware inverters. That applies to most popular STM32F1 devices like Naze32 and Flip32. Not only numer of UARTs there is limited, but also they lack hardare inverters. Of curse, everything is possible and hardware solution for Cleanflight, Naze32 and SmartPort telemetry can be found here.
Luckily, there is simpler solution for Cleanflight that uses SoftSerial and does not require any hardware hacks besides special wire. Requirements:
- Cleanflight capable flight controller (STM32F1 or STM32F3),
- SmartPort enabled receiver: FrSky X8R, X6R, X4R, X4RSB,
- Possibility to enable SoftSerial. Depending on FC type, different fetures like Parallel PWM, Sonar, LED Strip or Current Meter collides with SoftSerial functionality. Check documentation first. In case of Naze32/Flip32 WS2812b LED strips and Parallel PWM can not be used.
Continue reading Smartport telemetry for Cleanflight
When few weeks I wrote how to solve a problem of broken USB port in Flip32+ flight controller, I suggested that one of the solutions is adding a serial Bluetooth module to provide wireless connection with a bord. And telemetry. Excellent news is: this is pretty simple and cheap.
What we will need: