# RC transmitter and receiver for Raspberry Pi possible? [closed]

I've got a pet project in which I'm trying to write/build a self learning autopilot for my rc plane. I've got a Raspberry Pi with an IMU and a pitot tube in the plane and it can now control the servos of the plane. So far so good.

I'm now thinking about connectivity. I want to be able to send commands in json from my laptop to the Raspberry Pi in the plane. I got it working over wifi, but that means I need to take my router outside when I go flying. Plus the range of the wifi is not very good (I tested it outside and it comes to about 50 meters).

Does anybody know whether there are any simple modules which I can attach to my raspi and laptop to send json with this rc technology to and from the pi over a range of at least 200 meters? All tips are welcome!

## closed as too broad by brhans, Chris Stratton, Voltage Spike, Finbarr, Dwayne ReidJan 6 at 17:15

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• tiny antennas have tiny areas to gather in the EM energy. You need to use a much lower frequency than WiFi. – analogsystemsrf Dec 25 '18 at 0:31
• Most serious hobby RC gear uses the nRF24, its semi/compatibles, or incompatible competitors like the A7105 or (EOL) CYRF6936. But a pi is a grossly unsuitable choice for an autopilot. That is a job for an MCU with a simple software stack, not a desktop OS running off a flaky SD card. You also don't want json for control, rather compact binary packets. – Chris Stratton Dec 25 '18 at 1:14
• You will find the USB WiFi antenna's have much more range, but it will cost you a USB port on your Rpi, and a change in some files so eth0=wlan0, and shutdown the internal WiFi. The whip antenna may imbalance your rc plane. The above comments are important as well. Just creating a control panel (in Python 3) to flash some LED's in sequence used 10% of the CPU's resources. The Pi is a toy for children. It is not even a complete basic motherboard. It has no RTC. It has no shutdown sequencer unless you buy one as a pi-hat. It has no multi-task queue. Fast interrupts can damage the SD card. – Sparky256 Dec 25 '18 at 2:39
• @analogsystemsrf - but I see systems such as the Flysky fs-i6 with the FSiA6B receiver, which operate on 2.4GHz but according to some reviews still manage to get a range of 400meter to 4km on a clear day. Wifi is also on 2.4GHz, so why shouldn't I be able to get such a range? – kramer65 Dec 25 '18 at 6:19
• Look at LORA modules. (ICs available but modules better cost/benefit). One example. and A zillion examples – Russell McMahon Dec 25 '18 at 10:34

WiFi should be able to work well for your application.
ESP8266, ESP32 and their kin should be suitable. Operation with external antennas at 2.4 GHz can achieve ranges of many km - especially in ground to aerial operation.

But, look at LORA ("Long Range") modules which should easily meet your needs.
LORA - Wikipedia. Ranges of "over 10km in rural areas" are cited (antennae unspecified) but there is every reason to expect that this range can be exceeded in ground to air operation with 'sensible' antennae.

LORA utilises 'spread spectrum' techniques to achieve astounding-but-true real-world link budgets of typically 168 dB. eg -148 dBm RX levels at 100 mW tx power (!).

ICs are available but modules offer vastly better cost-benefit. There are numerous on web Raspberry Pi + LORA related pages.

A zillion examples

Digikey - LORA modules - wow!!!

Seeed Studio module from Digikey - $US7.91/1 in stock (!) Datasheet for above - github Raspberry Pi LORA-GPS module -$35 Digikey. Adds LORA to RasPi and can add GPS functionality with GPS input to RasPi serial port. When are you buying one ? :-).

Wiki for above

LORA SPECIFICATION

Lora Specification for above RasPi module:

168 dB maximum link budget. <- !!! (!!!!!) +20 dBm - 100 mW constant RF output
+14 dBm high efficiency PA.
Programmable bit rate up to 300 kbps.
High sensitivity: down to -148 dBm. <- natural consequence of power and link budget
Bullet-proof front end: IIP3 = -12.5 dBm.
Excellent blocking immunity.
Low RX current of 10.3 mA, 200 nA register retention.
Fully integrated synthesizer with a resolution of 61 Hz.
FSK, GFSK, MSK, GMSK, LoRaTM and OOK modulation.
Built-in bit synchronizer for clock recovery.
Preamble detection.