That my list of 9x radio mods, Keeping it DIY, and under $200 :)
First one is 'er9x' firmware super easy:
also you can use arduino board.
'eepe' tool is here.
Next one is the 6 position 'mode' switch for ArduPlane/Copter, here is my original mod and complete 'how to' from Paul. That is 2 pole switch, so its 2 switches in one and I used that second switch for LEDs.
Just cut-off some of extra foam but don't try to completely remove it, big mess !
Speaker Mod with Haptic Feedback really cool one :)
Next FrSky Telemetry
There is number of ways to do it 'How to modify your 9x to support telemetry'
one is using 'FrSkyLite' that also used for 'FrSky' firmware upgrades.
But here is another one that also converts 'FrSky' module to support firmware upgrades via FTDI cable.
You'll need to perform minor surgery on that DHT DIY module :)
And some work on the 9x board too.
But the most important part is the new ERSKY9x ARM board for 9x radios !!!
Here is a Feature List:
input voltage 6.5 - 16 volts (7.2V ideal)
Atmel SAM3S ARM Cortex M3 Microprocessor
256K of Eprom , 48K Ram
4mb EEprom - For Model /sound storage
Support for Optrex display F-55472GNFJ-SLW-AAN
Built-in external USB socket for Programming / interface.
2 external RS232 Serial Ports.
PWM control of LED backlight . (dimmable)
1/2 Watt Mono Audio Amp , with digital volume control
8 ohm speaker output with auto switch over headphone jack output.
Micro SD card socket with 4 bit high speed connection to ARM
Support for RN-42 Bluetooth Module (spot for external TTL serial connection)
Haptic output connector , with PWM drive.
ATTiny167 AVR micro for RTC and 12 external switch inputs/encoders or up to 10 A/D inputs , can be battery backuped
External I/O connector with 4 lines one with DAC output
I2C output connector + spare port pin.
On board current sensor , to measure power usage on battery
Second PPM OUTPUT
Software control of Power - off
Should be out soon for $85 !