alt_vario

This high-precision altimeter/variometer is designed to work with Team Black Sheep's Crossfire and Tracer PWM receivers, and should also work great with any RC receivers that are able to speak the CRSF protocol at 416,666 baud, and transmitters that can receive and display it.

It uses an MS5607 barometer, and converts pressure to altitude. Since pressure changes quite a bit with the weather, its is recommended to zero-out the altitude value on your transmitter on every launch, and then view the relative altitude during the flight.

It sends CRSF messages to your transmitter for Altitude and Vertical Speed.

Altimeter Setup: To connect to your RC receiver, solder a short servo cable (or pin headers for a direct connection into your radio receiver) to the 3 pads on the altimeter. The square pad is Ground(-), then VCC(+3V to +6V), then Data. Optionally connect your Receiver's battery to the 2 additional pins for power and ground, to avoid having to plug your battery directly into your radio receiver. (See photo for pin-out.) Then make sure to cover the barometer chip such that air can circulate into the tiny holes, but light can not get in. Light leaking into the barometer can throw off the altitude data by tens of meters!

Radio Setup: Then set up your receiver's Output Map to set up the appropriate channels (3 & 4 for my nano RX) as CRSF RX and CRSF TX. Connect the altimeter to the CRSF RX channel's pins, since the receiver will be receiving CRSF data from the altimeter. The CRSF TX pins are unused, so I use those pins to connect my battery. Make sure your RC TX has Telemetry set to On. Then power up your plane and transmitter, and tell your transmitter to Discover New Sensors. It should find a few new sensors, and the ones you want to use are ALT and VSpd.

Then use this value as you want! I set up my transmitter's Discus Launch Glider model to speak the Alt sensor value 3 seconds after each launch, to get instant feedback on how high my launches are going, and then the Transmitter's Variometer watches the VSpd sensor to beep when I'm in rising or sinking air.

Board specs, without wiring or tape/heat shrink:
Size: 11mm x 22mm
Weight: 1.1g

Note that this product is unrelated to the UDB5mini/UDB6mini, and is meant for gliders/planes without a full flight controller.