Hi everyone, I'm very happy to announce something that 3D Robotics has been working on since late last year in cooperation with a few very talented developers. Today we are announcing the 3DR Radio telemetry system, an open-source alternative to XBee telemetry set-ups, with superior performance, great range and a much lower price (half the price of the equivalent Xbee kit).
This is a 2-way, half-duplex wireless communication system with a standard TTL UART interface, based on HopeRF's HM-TRP data link modules, and custom firmware that improves upon the module's original features and performance.
The SiK firmware includes a bootloader that permits radio firmware updates over the serial interface, and radio firmware with configurable parameters. Updates and configuration are fully supported in the APM Mission Planner (press control-A to bring up the window below), and also possible through AT commands.
From the wiki:
- light weight (under 4 grams without antenna)
- available in 900MHz or 433MHz variants
- receiver sensitivity to -121 dBm
- transmit power up to 20dBm (100mW)
- transparent serial link
- air data rates up to 250kbps
- MAVLink protocol framing and status reporting
- frequency hopping spread spectrum (FHSS)
- adaptive time division multiplexing (TDM)
- support for LBT and AFA
- configurable duty cycle
- builtin error correcting code (can correct up to 25% data bit errors)
- demonstrated range of several kilometres with a small omni antenna
- can be used with a bi-directional amplifier for even more range
- open source firmware
- AT commands for radio configuration
- RT commands for remote radio configuration
- adaptive flow control when used with APM
- based on HM-TRP radio modules, with Si1000 8051 micro-controller and Si4432 radio module
Kit price is $74.99:
Individual radios are $35.99 (USB) and $31.99 (pins):
Kits and radios are available for purchase today, and they will start shipping next week.
Coming soon: a 3DR Radio XBee footprint adapter for both frequencies, compatible with our USB XBee adapter and Sparkfun's XBee Explorer boards.
We will also be releasing a version of the radios on both frequencies with an Xbee-compatible footprint, so you already have Xbee adapters, you can use them.
We hope you enjoy using these radios as much as we have during development, the simpler hardware and configuration tools compared to XBee provide a much smoother experience. We look forward to hearing your comments!
Huge thanks to the developers who made this happen: Team leaders Andrew Tridgell and Mike Smith along with Michael Oborne, Seppo Saario, Marco Robustini and others.
Comments
@ Marco Robustini,
warning !!! you can't use 900 Mhz band as ISM band in ITALY It is busy for GSM communication ....
you shoud use 433Mhz or 868 Mhz Band
Oh, another thing: does the 3DR radio support three radios on the same network ID? Meaning two receivers, that don't confuse each other with their heartbeat or keepalive packets. I'm thinking if one integrated one telemetry receiver into the RC transmitter (like the Turnigy 9x, with er9x modded in) just for display of the most critical data, and having another on the laptop / groundstation for the full use of the link's capabilities...
This would enable you to fly with just the RC and still get all the critical information, like location, and systems and battery status, even without lugging along a full groundstation. Then if you do bring one, you still wouldn't lose battery level or RSSI alerts or whatnot on the RC transmitter, which might be the most handy thing to have them on.
@Simon,
The UK/Europe 433 rules allow for multiple choices for compliance. You have the following choices:
there are other choices as well, but these are the two that are most likely to be useful for UAVs.
The channel spacing requirement limits the AIR_SPEED that you can use to low values, as higher AIR_SPEED values will use a wider channel. You also need to make sure that NUM_CHANNELS is higher enough that the spacing between channels is less than 25kHz.
The duty cycle requirement does the opposite - to use a 10% duty cycle you need to use a relatively high AIR_SPEED in order to get decent telemetry rates.
These two choices are just two ways of the regulatory body trying to ensure that this narrow bit of spectrum can be shared by many users at once. The duty cycle option does this by ensuring that any one radio doesn't transmit more than 10% of the time. The channel spacing option achieves the same goal by ensuring there are lots of channel choices, so any one radio only uses a narrow slice of the spectrum at a time.
I suspect the best results will be to use the duty cycle option, but I haven't done enough testing to be sure. What I've done in the firmware is given enough flexibility in the configuration options to allow users to experiment to see what is the best option for UAVs. I'm hoping that the diydrones community will work together to find the best options.
Someone also asked about what range a 433 radio should expect at 10mW. The theoretical range should be quite good - well over a kilometre and possibly a lot more. This is because the path loss (ie. loss due to signal travelling through air) is much lower for 433MHz as compared to 915MHz. Roughly speaking, you can add 6dB to the number to get the equivalent 915 power level. So a 433 radio at 10mW (which is 10dBm) should have about the same range as a 915 radio at 16dBm (around 40mW). That should be plenty of range for line of sight UAVs.
I'm still doing 433 range tests. I have a problem at the moment with noise from my USB host controller on my laptop impacting the 433MHz USB radios (as my USB host controller is running at 480MHz, which is a bit closer to 433 than I would like). I'm trying some workaround for that at the moment.
Cheers, Tridge
Hello Simon,
Just to clear this point up a little, Tridge pointed out that there is a band here in the UK which can be used On page 17, this is the definitive statement of the regulations, However a few dealers and I are not looking into this point at the moment, the point we are looking at is about the radios being legal to import / sell and use here in the UK, EU and other places, we are looking to get to the bottom of the information from Ofcom, as it states that there needs to be a "CE" stamp to be approved for use in the UK / EU, once I / we can get to the bottom of this then I hope we can move onto the range and what it means to use the radios at 10Mw's with the 10% duty cycle and if there could be some form of clash with the other users in the same band.
Grips has turned up some interesting information a few posts back, I will be looking into this some more in the morning, I hope there is a way to move this forward with the radio units already using some parts that are already approved! :)
Regards
Martin
Reading the foregoing comments about the use of the 433MHz band in the UK has left me really confused.
Martin of BYOD says that it clashes with other allocations. Andrew suggests that a duty cycle of 10% is required.
I have used both APC220 and XRF modules for telemetry in this band taking as my guide to legality the OFCOM publication RA60 where it states :
5. Can I transmit data from the model?
Yes. Telemetry can be transmitted from general, surface or air models back to the controller. The band is 433.050 to 434.790 MHz; the maximum channel spacing is 25 kHz and the maximum radiated power is 10 mW. Please note that the band is not exclusive to model controllers - it is shared with other users, who are permitted to radiate relatively higher powers, so you must take care when selecting a channel for use in a particular locality.
No mention of duty cycle restrictions or prohibitions.
Can anybody point me towards a definitive statement of regulations?
@Rana, please can you talk more on the 10W 433Mhz telemetry, is it buyable?
Very nice product at very low price, 3DR strike again!
With this concentrated of technology I believe that XBee has a short life.
I am doing testing for days and never gave a single problem, the 900 MHz work super fine, tested today in open space, over 800 meters at very low altitude and without losing signal, over I could not see my big X8, at that distance was already a small black dot in the sky.
Thanks Sam and Alan for giving me the opportunity to test the product in preview, and to the whole team for the rest... :-)
I run to order additional modules for my quads!
Bests, Marco
This is a question for Andrew Tridgell, Sam or other dev. team member of the 3dr Radios:
The actual hardware that is radiating the radio frequency is the Si4432, is that correct? The HM-TRP has its own 100mw transceiver which is the Si4432? The air module seems to have two boards sandwiched together. Is the green one the HM-TRP and the purple one just an interface board? The ground module is everything composed into one.
Are these a similar design to the APC220 xbee replacements we have seen in the past?
I am asking in case we due manage to get the radios through the Industry Canada certification process.
@ penpen: the FTDI chip is larger, but at this point everyone knows how to use it (APM 1.x, older Arduinos, lots of Sparkfun and Adafruit products), and more than likely, everyone writing comments on this post has FTDI drivers already on their computer. Also, it's not using an external resonator.
In looking at the actual components being utilized, I see the following radio module
1. Silicon Labs Si4432. Here is a document related to the Hoperf Si4432 Transceiver. The linked page states, ``The Si4431 and Si4432 comply with FCC and ETSI requirements when used in any of the standard ISM Bands.`` Here is a link to all of the data sheets related to this radio module. It states, ``The direct digital transmit modulation and automatic PA power ramping ensure precise transmit modulation and reduced spectral spreading ensuring compliance with global regulations including FCC, ETSI, ARIB, and 802.15.4d regulations.``
So through the jiggs and the reels, here is the FCC certification document for the Si4432 chip.
Here is a link to the FAQ about FCC testing and its usage in Canada. It states the following:
Unfortunately, it looks like the documents were updated in 2007, not meeting the first criteria.
Here is a link to what appears to be the fee`s for certification. The process refers to a RSP-100 process.
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