FrSky Voltage Sensor

One of the reasons I choose to upgrade my Turnigy 9x to the FrSky system was the telemetry(2-way) mode. This gives me signal strength data and most of all, the RX has two analog ports. These two analog ports (3.3v!) can be used for anything with a range of analog values. For example, with a few resistors, i made a voltage divider so that the 12.6v of a lipo is scaled down to 3.3v where it is then sent to the 9x and read out as a battery voltage on the 9x lcd. no need for lipo alarms! I have the ER9x firmware which made the frsky mod possible. also required here.

RX Setup

Here is the schematic. The color dots are the resistor color codes. AIN is A1 or A2 on the RX. Only connect one +. so if you had a 3s batt, you would connect it 12v+ to the 3s resistor.

TX Setup

Hardware Setup

-Build the above circuit for the battery you are using

-Connect it to the battery and RX(dont mess up polarity!)

Turn on your TX

-Power the RX with a bec or something

Voltage Calibration 

model page 10/12 (Telemetry 1)

-A1 channel 11.1v 13.0 line is showing the voltage of the battery 11.1v is a calibration value, 13.0 in this example is the actual battery voltage it reads.
-To set this up, measure the voltage of your battery with a volt meter. 

-Now this voltage should be in this screen. adjust the 11.1v number until the 13.0 number is equal to the volt meter reading

-press exit when done. now you have "calibrated" A1. 

-also, the the "v" from 11.1v can be changed to A for ex to measure the amps the model is drawing (with that amp sensor of course).

Alarms

alrm --- < 0.0v
alrm  --- < 0.0v

These are alarms you can set so it will beep when it is below certain level. 

-Select the "---" and choose yellow, orange or red. these would be the level of the battery. 

-Now, you can change the sign (< or >)most people will use less than (<) then you could set the 0.0v parameter to the a voltage that is related to the yellow orange or red. FOR example

alrm Yel < 11.1v 

this means you would have a yellow alert when the battery on the model drops below 11.1v

alrm Red < 10.0v 

this means you would have a red alert when the battery on the model drops below 10.0v
alrm Yel > 11.1v

this means you would have a yellow alerrt while the battery on the model is above 11.1v
alrm Red > 10.0v

this means you would have a yellow alert when the battery on the model is above 10.0v

Same for if you had a battery on A2

Model page 11/12 (Telemetry 2)
-TxRSSIalarm is a value to set for when the TX signal is less that whatever value. lets you know when youre going out of range
-RxRSSIalarm is the same for telemetry signal from the rx

-mAhalarm is for alarming you when you have drawn x amount of amps from the battery
-ALTalarm is for if you have a baro sensor and it will alarm you if you have gone too high.
-gpsaltmain uses the gps as a baro instead of the separate baro

-Custom Menu this allows you to change what values show on your Telemetry screen while using the TX. i did A1 A2 RSSI and TSSI

will add more pics :)!!