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Mr.RC-Cam

Hexenbiest : Open Source Antenna Tracker / Ground Station OSD Project

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The Hexenbiest DiY open source project is an Arduino shield for a FPV ground station. It has A/V ports for up to six video receivers, OSD (on screen display) for menus and telemetry data, several user interface control methods (IR, R/C, Joystick), multiple video outputs, support for an external camera / mic, and more.

I will post the hardware design (schematics and BOM) and offer technical advice. I even have a small number of unpopulated PC boards (without components) I can offer at low cost to help move things along. But due to their limited number these are reserved for rc-cam members that have the skills to solder the SMD components and are serious about contributing code to help launch the project.

UPDATE: See this post for hardware design docs: http://www.rc-cam.com/forum/index.php?/topic/4018-hexenbiest-open-source-antenna-tracker-ground-station-osd-project/?p=28022

Just to be clear, this is a hardware design that is begging for software. I'm here to drum up some excitement and invite creative programmers to help build their dream FPV ground station in the spirit of open source sharing. But this won't happen without software (and hardware) contributions from like-minded hobbyists.

The project is called Hexenbiest. It is configured as a plug-in motherboard "shield" for an Arduino MEGA2560-R3 microprocessor board. Sorry to disappoint that it doesn't use a BeagleBone, Rasberry Pi, or other high-end CPU. The Arduino was chosen because of the huge community expertise and bargain price. But of course you are free to use this project to create your own hardware variant using the CPU you want. After all, this will be an open source project.

Here is a photo of the assembled board (click it for larger view).

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Project background (skip to next post if you hate infomercials):

The number of DiY open source projects for R/C and FPV is staggering. Some are software variants for popular open source hardware platforms (i.e., minimOSD). Just as brilliant are those super-charged firmware upgrades that turn low cost devices into magnificent performers (i.e., OpenTX). From my observation many got their start by the availability of some interesting low cost hardware; The software developers recognized the potential of doing something big with the hardware and went to work. Fantastic open source communities have been created this way. We can do that too!

Over the years I've dreamed of a flexible hardware platform for a FPV ground station that would be substantially software driven. The common theme in this vision has always involved multiple FPV receivers and OSD features. The idea is to push most of the functionality into the software and minimize the hardware the user would have to build. The reason for this is there are a lot more experienced programmers out there than hardware designers. And best of all, popular open source projects attract the attention of the Chinese cloners; Cheap software-ready hardware is eventually sold to us hobbyists; Then it's all about the software and there is no need to build anything!

Edited by Mr.RC-Cam
Added link to hardware docs

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The board's hardware I/O ports are summarized in this photo:

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The MEGA 2560 is a "High End" Arduino microcontroller that costs less than $15 USD on eBay. It plugs into the bottom of the board. In case you did not know, plug-in boards are called "shields" in the Arduino world. Here's a view of how the Arduino is installed on the Hexenbiest shield board:

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Some users may want to expand the shield board and add more hardware features. No worries, all of the Arduino's CPU pins are available from the Hexenbiest shield. So anything and everything is possible.

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Up to six video receivers (vRx's) can be installed. Some installations may only need one. Others may want to use two for classic diversity operation. Or install several receivers for servo-less antenna tracking. For example, install all six vRx's in a evenly spaced compass pattern for 360 degree coverage using high gain directional antennas. Or install five pointed in a horizon view and aim the sixth vRx straight up. The implementation that is used will involve software; It could be menu configured or hard coded. Remember, this is a software driven project and you have to write the code to do what you want.

The intended vRx is the FatShark Dominator goggle type module that has an RSSI (Received Signal Strength Indicator) output. This 5V powered module is currently offered in the 2.4GHz and 5.8GHz RF bands for about $40 USD each. Soon it will be available for 1.3GHz. Unfortunately the new 1.3GHz module does not have an RSSI feature, but hopefully the module can be hacked to provide it. And for those that like the cheap SkyRF/Boscam DiY modules, they are compatible too (they have RSSI).

The Fatshark 5.8GHz module's RSSI pin is located on a pad along the side of the module, as shown below. The RSSI pin location will vary with the module that is used, so check the datasheet.

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Here's a photo of a FatShark vRx module after it is wired for use on the Hexenbiest:

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The vRx modules are connected by a wire harness so you can place them anywhere on your ground station chassis. This eliminates the need for coax extensions on the antennas, which prevents RF losses from the coax.

There are other ways to use Hexenbiest, so be prepared to think out-of-the-box. Just to help describe how flexible things can be, imagine a ground station that can easily switch between different frequency bands. For example, install any combination of 2.4GHz and 5.8GHz vRxs. When you want to fly on 2.4GHz video then select it from the OSD menu. Changing to 5.8GHz would be as simple as selecting it from the alternate OSD menu choices. The software would configure the hardware to use the vRx modules that are appropriate for the desired frequency. Of course someone has to create this feature, why not you?

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The Hexenbiest has an OSD (MAX7456) for displaying menus, alarms, telemetry data, or anything else you need to see. If you want to implement a user interface then there are ports for a R/C receiver, 3-axis joystick, or IR TV remote.

For example, here's a compatible joystick that is only $2 USD from eBay suppliers. The XY axis have pots and the Z axis is a tactile push switch. Perfect for moving through menus and making selections.

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How about a handheld IR "TV" remote with IR receiver for under $3? No problem, eBay has it. This can be used as an alternative to the Joystick.

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And finally, you could plug in a R/C receiver and use your R/C Tx's sticks or toggle switches instead of the eBay Joystick. Regardless of the UI control method used, software is needed to implement these things.

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Hexenbiest also offers a local video camera and microphone feature. It can be used to record your narrations before/during/after a flight or to get a ground station view of the flying aircraft. Enabling the camera and/or mic could be controlled by a spare channel on your R/C Tx. Or use the other user input methods (joystick, IR remote).

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That's a quick summary of the Hexenbiest project. At this point I am testing the assembled board to ensure that all the circuitry is Ok. So far it is looking good, but there are few remaining things that need to validated. The only software I have written is some simple code to test the hardware, so a working system is not possible without software contributions from the community. If there is no interest then this project may never see the light of day.

Are you interested in it? If so, post your comments below. Do NOT email or PM me. In order for a project like this to get attention from possible contributors they will no doubt want to see there are others interested in it too. So post your comments in this discussion and help drum up some excitement!

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In case someone is waiting for an update, I can report the hardware validation is complete. All the PCB's audio/video circuity has been tested and seems to work well.

Hardware design documents have been posted. Please see this post:

http://www.rc-cam.com/forum/index.php?/topic/4018-hexenbiest-open-source-antenna-tracker-ground-station-osd-project/?p=28022

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