I-Bus Altitude Sensor for FlySky Telemetry

Requirements

• FlySky transmitter with AFHDS-2A telemetry. Preferably FS-i6 with modified firmware from qba667.
• Receiver with I-Bus sensor input, such as FS-iA6B. No firmware modification required.
• Atmel AVR-based board. Tested with SparkFun ProMicro clone, and Arduino Nano clone. ProMicro is about the lightest but powerful ATmega-based board. Nano is a bit heavier, but it has 3.3V dedicated output, so that it can be directly used with BMP-280 breakout board.
• Supported pressure sensor with I2C on a break-out board. Currently supported is BMP-180 on a GY-68 board, and BMP-280 break-out board. The later is more precise, but it requires 3.3 V power.
• 390K and 15K resistors for voltage divider for reading the battery voltage (optional).
• some wires and a 3-pin servo female connector for I-Bus.
• AVR toolchain (avr-gcc, avr-libc, avrdude, make, ...).

Wiring

Here is how to connect things together:

And here is my (rather messy) real-world example in Sky Surfer 1400:

Here is the version with Arduino Nano and BMP-280:

Firmware

The firmware is based on the following libraries:

• AVR BMP085 library by Davide Gironi
• AVR BMP280 library by Yours Truly.
• I2C/TWI master library by Peter Fleury

The I-Bus code is in the main file ibus-sensor.c. It provides the following sensors:

• Temperature sensor from BMPxxx
• Altitude relative to the power-on value
• Absolute altitude (reported as GPS-Altitude sensor)
• Maximum relative altitude reached since power on
• Climb rate
• External voltage (can be used for battery voltage alarm; optional)

It also provides visual feedback about the main loop (on-board Tx LED) and the I-Bus communication (on-board Rx LED).

Edit the Makefile to set up the exact AVR board version and pressure sensor used.

License

This project, is licensed under the terms of GNU General Public License, version 2 (only). See the file COPYING.

Author

Written by Jan "Yenya" Kasprzak.