Rebuild of this amazing little transmitter to OpenAVRc system inside. OpenAVRc is based on OpenTX 2.1.8, but customized for ATmega2560 MCU, which is inside now. Transmitter supports voices (own voices with numbers like speed, voltage, time,...), it has haptic vibrating motor, and also 4in1 multimodule, which support almost all known protocols like FrSky, Devo, FlySky and many toys copters protocols based on NRF24L01 chip.
Original MCU and RF module was removed. Actually from original FSi6 was used everything, what you see from outside, LCD and the circuit board.

Used parts:
(banggood.com)
Transmitter FSi6 http://goo.gl/M6i955
Multimodule 4in1 http://goo.gl/1qbJtQ
MP3 voice module https://goo.gl/dm6mQs
DC 5V booster https://goo.gl/cUjg4x
(aliexpress.com)
Mini speakers https://goo.gl/ZYQ3R9
Haptic https://goo.gl/CbH1xy
ATmega2560 pro mini https://goo.gl/LfxmTq

On the ATmega is sticked 5V to 3,3V converter, which is only 13x resistor divider for LCD data pins.