Event38 Bluetooth Telemetry Bridge Review

April 6, 2014 14:52 | By | Add a Comment

After a successful Kickstarter campaign, Event38 set out t0 eliminate the need for laptops on the flying field. Sure you can use bluetooth to control and monitor your drone, but that only gets you how far, 30 meters, maybe 40? If you want to use a 430MHz or 900MHz telemetry transmitter, you need an android tablet/phone capable of USB host mode, AND it’s another thing connected to your mobile device.

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Event38’s Bluetooth bridge eliminates all this by offering you a simple self-contained, self-powered device you can just bring to the flying field, clip onto your belt and forget about, using your phone or tablet to control even the most complex and demanding Drone missions. But is the $140 price tag justified? Find out in our in-depth review after the break!

Operating Principle

There’s not much to this device really: The Bluetooth bridge consists of a Bluetooth module and a telemetry radio in a frequency band of your choice – you have to specify whether you want the 430MHz or the 900MHz version when ordering. The two are connected via simple serial RX/TX lines. Your mobile device binds and connects to the Bluetooth transceiver. Any data sent to it is being retransmitted via the telemetry radio, and vice versa. This extends the range of telemetry to about 1 km. You simply pair your mobile device to the Bluetooth device “Event38” which appears when you turn on the unit. There’s no need to enter any pairing codes.

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Hardware Overview

The Bridge is a neat little self-contained device. People looking for fancy blinkenlights and indicators will be disappointed.

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There’s an RP-SMA jack for the antenna, an indicator LED showing the charge status of the built-in LiPo, a micro-USB connector for charging, and a physical power switch. Event38 gets bonus points for the physical switch which isn’t too easy to snag on, so it won’t turn off accidentally. A look inside reveals a very tidy job in electronics design.

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Alongside the 1000mAh 1S LiPo is the main board, containing the charging circuitry , Bluetooth radio, and telemetry radio module. The good: There are pads for anything you might want, including the serial data connections of both radios. This may well come in handy in the future. The LiPo also features a protection circuit, so there’s no way to completely kill the battery by accidentally leaving the unit turned on.

The bad: The micro USB connector is designed to be physically supported by a case. It is not meant to be soldered onto a PCB without some form of support keeping it in place, as repeated connects and disconnects will eventually wear out the solder joints. This may sound like a minor oversight, but our experience with Crius AIO boards has proven why the designers of this connectors don’t support this kind of use. As a quick fix, a dab of hot glue over the connector and PCB will help a lot in keeping the connector from breaking off the PCB. While you’re at it, you might want to secure the solder joints of the LiPo battery on the back of the PCB as well.

Charging the LiPo is a slow affair – the charge current is very low and it may take 5 hours or more for a full charge. Note that the LED lights blue when charging, irrespective of the current charge state. Switching on the device will make the LED blink red, yellow or green, corresponding to the LiPo charge status. Event38 states that continuous operation of up to 10 hours should be possible – while we haven’t tested the exact run time, we can say that after about 5 hours of flying the LED changed from green to yellow, so 10 hours does not seem too far fetched.

Setup

This is the part where things get a little bit cumbersome. Basically you have to configure the 3DR telemetry radio parameters to match your airborne transmitter. The USB connector is a bit misleading because it is really only used for charging. What we had to do to get going was connect our existing USB telemetry transmitter, read out the parameters, and then write those same parameters to the Bluetooth bridge via… well.. Bluetooth.

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The way this procedure works is as follows: Connect your USB Telemetry transmitter and note the com port assigned to it. Then bind the bluetooth bridge and also note its com port number. Then, start APM Mission Planner, go to the initial setup page, and select the 3DR Radio configuration. Set the com port of your USB transmitter, press the “Load Settings” button (Do NOT press Connect on the top right!), then wait until the values are all read successfully. You may need to set your Baud rate to 57600 or lower.

After that, change the COM port on the top right to the Bluetooth serial device of your Bridge, and press the “Save Settings” button – and you’re done! Note that you don’t have to fiddle with the “remote” side in the config.

Thankfully, Event38 hosts a brief but informative wiki page on the device on their wikispaces site.

Verdict

The Event38 Bluetooth Bridge worked flawlessly and is perfectly suited for the flying field. It even has the appropriate holes in the rubber casing to allow securing it on your belt. Having to lug around a laptop to interface with 430/900MHz telemetry system used to be a pain, and this nifty little device really trims down the amount of needed hardware. It’s a bit sad that Event38 didn’t go the extra mile to add an FTDI interface to the USB port so it would be possible to configure settings via USB as well as charge. As it is, the asking price of USD $140.- may be a bit steep, considering we’re talking about hardware costs of around $70. On the plus side, it really is a self-contained unit with a custom PCB in a solid case. Perhaps people who don’t shy away from building their own hacks have little use for this, since it’s trivial to connect the two radio modules together and get a LiPo battery plus charging circuit for a few dollars off ebay. But for those who’d rather get a finished device to finally leave your laptop at home when doing complex waypoint missions, this product is not a bad choice.

What we liked:

  • Solid build
  • Simple operation
  • Good range (approx. 1km at 100mW transmit power)
  • Battery lasts for an entire day of flying
  • PCB is hacker-friendly

What we didn’t like:

  • USB charging is very slow, port used for charging only
  • USB connector should be physically secured to the PCB
  • Requires familiarity with 3DR transceivers to set up

Where to buy

If this device caught your interest, you can order it from the Event38 website right now.

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