FrSky Telemetry with Er9x; short explanation
Posted: Sat Feb 25, 2012 10:56 am
This post describes the Er9x FrSky NOHT firmware when used to display Rx Battery Voltage, Pack Voltage and Altitude when using the Winged Shadow "How High" sensor. This version of ER9x has no Helicopter firmware and no templates. This save space in the ATMEGA chip for the telemetry firmware and more model memory, I suppose.
This description focuses on an electric powered glider or aircraft with either a separate pack for Rx supply or a UBEC connected to the main power pack. Of course the description is generally applicable too. Altitude is important to me as I sometimes compete in F5J where there is a vast increase in penalty for starting altitudes over 200 feet.
No hub is necessary to obtain these displays on the transmitter screen. You will need to buy an altitude sensor and make a voltage divider. I decided to use a stand alone telemetry system for a variometer because I wanted real time audio output without having to look at the screen. My descriptions of this system is here:
http://www.rcgroups.com/forums/showthre ... st20569858
See posts #30 and #36. Of course both the altimeter and variometer are illegal for competition but are very useful for training.
You get the three Received Signal Strength Indication (RSSI) alarms for free, ie without doing anything special or buying sensors. They are not adjustable. As the distance increases you get one beep, then two, then three. Be aware that when the Rx swops over from ariel to ariel ie is using the built in ariel diversity feature of the Receiver chip you get a single beep at the Tx: nothing to worry about but may still be an indication of good or not so good positioning of the ariel on your model. When circling it can happen twice per circle which gives the clue that it is Rx ariel diversity working.
Get worried when you hear the triple beep in flight. To become familiar with the alarms do a range check by walking away from the model with the Tx in your hand in range test mode. This will give you a sense of the proportions of the distances when each alarm sounds and when you finally lose contact.
To display altitude a Winged Shadow "How High" unit is programmed for the correct output and connected into the receiver as described in the How High documentation. Power is taken from one of the receiver channels and the output, a single lead with a male plug, plugged into the signal pin labelled Rx on the side of the FrSky receiver. Despite the right click 9/10 screen having selectable options for metric or Imperial display the display only works with imperial. So the "How High" has to be programmed to Imperial mode and the right click 9/10 screen selected to display "Imp".
The Rx voltage is displayed on the screens when you put a jumper (shorting plug) across the A1 + and A1 Signal pins on the side of the FrSky receiver so that is easy too. The voltage comes up on the display and has two alarms which you can set as well at right click 9/10 screen. You have to calibrate the A1 voltage multiplier on that screen so that the reading you get with your voltmeter at the Rx agrees with the telemetry displayed value at the transmitter.
To display pack voltage take some leads off the main battery pack connector through a voltage divider to give less than 3.3 Volts at the A2 pins. You then have a readout of the main pack voltage. Again you have to calibrate the voltage multiplier on right screen 9/10 in eR9x so that your voltmeter reading agrees with the screen display. This voltage readout is handy for a day's soaring so that you don't run the main pack too low ie do too many climbs. You can set two levels alarms for this telemetry channel too. I suggest using a trim pot for one of the resistors so you can get fairly close to just under 3.3 Volts at the Rx side terminals. A voltage divider is explained in the posts mentioned above for the Variometer.
Just an observation about the right screen 9/10 voltage multiplier values. Highlighting any value using the left side navigation keys and then pressing the top right (enter) key gives you the ability to toggle between a number of alternatives or set numeric values for the voltages alarm numeric values. When finished press the lower right key short to set the value and long to return to the main screens. There's a lower case v and an upper case V option as well as upper case A for current (Amps). For very large multiplier values use V which goes up to 60 Volts I think. For smaller values use v which goes up to 24 Volts I think. The value you have to use is a mystery to me and the value to enter for the v option is about twice the real Voltmeter reading.
Another point; the minimum and maximum values of the voltages, (and also RSSI and TSSI readings) are shown below the instantaneous value. Also the instantaneous value of A1 drifts a bit while calibrating it compared to the actual Voltmeter reading. I have had to set and reset the multipliers a few times over a period of two or three minutes to get a good average display which corresponds with reality.
Here are the three screens for the FrSky Telemetry.
Descriptions are for the pictures below.
Mutchy
This description focuses on an electric powered glider or aircraft with either a separate pack for Rx supply or a UBEC connected to the main power pack. Of course the description is generally applicable too. Altitude is important to me as I sometimes compete in F5J where there is a vast increase in penalty for starting altitudes over 200 feet.
No hub is necessary to obtain these displays on the transmitter screen. You will need to buy an altitude sensor and make a voltage divider. I decided to use a stand alone telemetry system for a variometer because I wanted real time audio output without having to look at the screen. My descriptions of this system is here:
http://www.rcgroups.com/forums/showthre ... st20569858
See posts #30 and #36. Of course both the altimeter and variometer are illegal for competition but are very useful for training.
You get the three Received Signal Strength Indication (RSSI) alarms for free, ie without doing anything special or buying sensors. They are not adjustable. As the distance increases you get one beep, then two, then three. Be aware that when the Rx swops over from ariel to ariel ie is using the built in ariel diversity feature of the Receiver chip you get a single beep at the Tx: nothing to worry about but may still be an indication of good or not so good positioning of the ariel on your model. When circling it can happen twice per circle which gives the clue that it is Rx ariel diversity working.
Get worried when you hear the triple beep in flight. To become familiar with the alarms do a range check by walking away from the model with the Tx in your hand in range test mode. This will give you a sense of the proportions of the distances when each alarm sounds and when you finally lose contact.
To display altitude a Winged Shadow "How High" unit is programmed for the correct output and connected into the receiver as described in the How High documentation. Power is taken from one of the receiver channels and the output, a single lead with a male plug, plugged into the signal pin labelled Rx on the side of the FrSky receiver. Despite the right click 9/10 screen having selectable options for metric or Imperial display the display only works with imperial. So the "How High" has to be programmed to Imperial mode and the right click 9/10 screen selected to display "Imp".
The Rx voltage is displayed on the screens when you put a jumper (shorting plug) across the A1 + and A1 Signal pins on the side of the FrSky receiver so that is easy too. The voltage comes up on the display and has two alarms which you can set as well at right click 9/10 screen. You have to calibrate the A1 voltage multiplier on that screen so that the reading you get with your voltmeter at the Rx agrees with the telemetry displayed value at the transmitter.
To display pack voltage take some leads off the main battery pack connector through a voltage divider to give less than 3.3 Volts at the A2 pins. You then have a readout of the main pack voltage. Again you have to calibrate the voltage multiplier on right screen 9/10 in eR9x so that your voltmeter reading agrees with the screen display. This voltage readout is handy for a day's soaring so that you don't run the main pack too low ie do too many climbs. You can set two levels alarms for this telemetry channel too. I suggest using a trim pot for one of the resistors so you can get fairly close to just under 3.3 Volts at the Rx side terminals. A voltage divider is explained in the posts mentioned above for the Variometer.
Just an observation about the right screen 9/10 voltage multiplier values. Highlighting any value using the left side navigation keys and then pressing the top right (enter) key gives you the ability to toggle between a number of alternatives or set numeric values for the voltages alarm numeric values. When finished press the lower right key short to set the value and long to return to the main screens. There's a lower case v and an upper case V option as well as upper case A for current (Amps). For very large multiplier values use V which goes up to 60 Volts I think. For smaller values use v which goes up to 24 Volts I think. The value you have to use is a mystery to me and the value to enter for the v option is about twice the real Voltmeter reading.
Another point; the minimum and maximum values of the voltages, (and also RSSI and TSSI readings) are shown below the instantaneous value. Also the instantaneous value of A1 drifts a bit while calibrating it compared to the actual Voltmeter reading. I have had to set and reset the multipliers a few times over a period of two or three minutes to get a good average display which corresponds with reality.
Here are the three screens for the FrSky Telemetry.
Descriptions are for the pictures below.
Mutchy