New Products Flash Sale
Thread Tools
Old Jun 30, 2015, 11:07 AM
Auvidea is offline
Find More Posts by Auvidea
Registered User
Auvidea's Avatar
Germany, BY, Denklingen
Joined Mar 2015
16 Posts
Discussion
Pixhawk 2 - design of a general purpose carrier board

Hi there,

24 days ago, the hardware design of the upcoming new Pixhawk 2 flight controller was published on Github, as the hardware design is open source.
https://github.com/PX4/Hardware

The main difference to the Pixhawk is, that all connectors have moved onto a single 80 pin Molex connector (DF17(3.0H)-80DS-0.5V(57)). Molex has designed this new connector especially for mechanically critical applications. Molex: "... greatly enhanced the resistance to the drop shock."
http://www.hirose.co.jp/cataloge_hp/...7_20130411.pdf

Further enhancements are redundant sensors. Also on Github there is the design of a separate sensor board which attaches with flexible PCBs.
https://github.com/PX4/Hardware/blob...om%20Above.PDF

Now the question comes up, how would you connect your hardware to this 80 pin connector? I am currently investing whether I should take action here. I am considering designing a carrier board for this new Pixhawk 2. I would like to start a discussion on the following topics:
  • what should be the basic features of this carrier board?
  • what connectors should it use (many do not seem to like the "robustness" of the DF13 connectors on the original Pixhawk)?
  • step-down power controller from 6S to power the Pixhawk 2?
  • integration of 1 milliOhm resistors to measure battery current
  • what should be the form factor?
  • feel free to add more to this list ...

I would love the idea, of integrating all electronics onto a single PCB which becomes part of the multirotor frame itself. This would eliminate a lot of cabling and many connectors which possibly could fail. But it would be subject to vibration. So this only might be an option for very small multi rotor devices.

Pixhawk 2 enhancement
Also I am in a position to customize the Pixhawk 2 hardware. However the compatibility should not be compromised. But one possibility would be, to go back to a design with individual connectors like the original Pixhawk has. But maybe with a different kind with higher reliability. Any ideas or proposals?

Addition of new features
  • integration of a brushless gimbal controller (Alexmos)
  • integration of H.264 video encoding with low latency live streaming
  • HD OSD of flight controller data (MAVLink)
  • control of PTZ cameras

I am looking forward to hear from you. Any inputs are welcome.

Jurgen
Auvidea is offline Find More Posts by Auvidea
Reply With Quote
Sign up now
to remove ads between posts
Old Jun 30, 2015, 11:57 AM
mike_kelly is offline
Find More Posts by mike_kelly
Wisconsin
United States, WI, Hayward
Joined Jan 2012
1,674 Posts
Quote:
Originally Posted by Auvidea View Post
Hi there,

24 days ago, the hardware design of the upcoming new Pixhawk 2 flight controller was published on Github, as the hardware design is open source.
https://github.com/PX4/Hardware

The main difference to the Pixhawk is, that all connectors have moved onto a single 80 pin Molex connector (DF17(3.0H)-80DS-0.5V(57)). Molex has designed this new connector especially for mechanically critical applications. Molex: "... greatly enhanced the resistance to the drop shock."
http://www.hirose.co.jp/cataloge_hp/...7_20130411.pdf

Further enhancements are redundant sensors. Also on Github there is the design of a separate sensor board which attaches with flexible PCBs.
https://github.com/PX4/Hardware/blob...om%20Above.PDF

Now the question comes up, how would you connect your hardware to this 80 pin connector? I am currently investing whether I should take action here. I am considering designing a carrier board for this new Pixhawk 2. I would like to start a discussion on the following topics:
  • what should be the basic features of this carrier board?
  • what connectors should it use (many do not seem to like the "robustness" of the DF13 connectors on the original Pixhawk)?
  • step-down power controller from 6S to power the Pixhawk 2?
  • integration of 1 milliOhm resistors to measure battery current
  • what should be the form factor?
  • feel free to add more to this list ...

I would love the idea, of integrating all electronics onto a single PCB which becomes part of the multirotor frame itself. This would eliminate a lot of cabling and many connectors which possibly could fail. But it would be subject to vibration. So this only might be an option for very small multi rotor devices.

Pixhawk 2 enhancement
Also I am in a position to customize the Pixhawk 2 hardware. However the compatibility should not be compromised. But one possibility would be, to go back to a design with individual connectors like the original Pixhawk has. But maybe with a different kind with higher reliability. Any ideas or proposals?

Addition of new features
  • integration of a brushless gimbal controller (Alexmos)
  • integration of H.264 video encoding with low latency live streaming
  • HD OSD of flight controller data (MAVLink)
  • control of PTZ cameras

I am looking forward to hear from you. Any inputs are welcome.

Jurgen
I think the industry desperately needs to move to a "motherbrd" design with modules like the FC having a standard connection. As long as the manufacturers conform to the standards a user could plug in the fc, rcvr, gimbal controller, GPS etc from any manufacturer. No cables to transmit noise or get interfered with. No useless non-locking connectors on cables that fall out.
mike_kelly is offline Find More Posts by mike_kelly
RCG Plus Member
Old Jun 30, 2015, 02:50 PM
crayfellow is offline
Find More Posts by crayfellow
Registered User
Joined May 2015
39 Posts
Part of my research project is to find some standardized "open source" means for FC and a central onboard general purpose computer to interact. Initially I am using Pixhawk and Beaglebone Black (Rev C). Would you guys have any interest in collaborating?
crayfellow is offline Find More Posts by crayfellow
Reply With Quote
Old Jun 30, 2015, 10:30 PM
Auvidea is offline
Find More Posts by Auvidea
Registered User
Auvidea's Avatar
Germany, BY, Denklingen
Joined Mar 2015
16 Posts
standardized motherboard design

Thank you for this feedback. I like the idea of a standardized motherboard type of design, so that users can plug in various modules as needed. I think that the Pixhawk 2 has defined a good physical spec of a flight controller module. So it should be possible that other flight controllers such as the Autoquad for example conform to the same specification (mounting holes, connector pinout).

The gimbal controller would have a second place to go. It could share the size and mounting holes. But it may want to use a different connector, so it cannot be plugged into the flight controller socket. Also it requires a different set of signals (3 brushless motors). Possibly the same connector but with a different pin count could be used. Maybe the 30, 40 or 50 pin version would be appropriate.

Also some are looking for adding a central onboard general purpose computer. This could go onto a third socket. crayfellow is looking at the Beaglebone. Now this does not fit nicely mechanically. I would rather like to implement a tiny CPU module like the Raspberry Pi compute module or the HummingBoard compute module or the Dartboard compute module. These CPU module are all small in size and one could design an individual carrier board, to make all of these mechanically compatible, so that they can be plugged into one socket on the motherboard.
Last a socket for a Wifi networking module may be appropriate. To add something like the Carambola 2 or a Chinese build wifi module with an integrated 5 port Ethernet switch. I have such designs in the works.

So in total we are now looking at a motherboard with 4 sockets:
  • flight controller socket (35x35mm) - Pixhawk 2 compatible
  • gimbal controller socket (35x35mm) - like the Alexmos BGC
  • general purpose CPU socket (35x60mm) - e.g. RPI, iMX6, ...
  • Ethernet switch and wifi module (35x60mm) - first 2.4 GHz, later 5 GHz

It needs to be evaluated whether the 35x60mm size is sufficient to fit various CPU module or Wifi modules. Possibly it needs to be increased slightly.

These 4 sockets could be arranged in a 2 by 2 setup. So the total board size requirement would be 72 x 97mm (with 2mm spacing between the modules). All would use the same kind of Molex connector, but of different size and placement, so they cannot be misplaced.
Auvidea is offline Find More Posts by Auvidea
Reply With Quote
Old Jul 02, 2015, 09:02 AM
twbrkfd1 is offline
Find More Posts by twbrkfd1
Registered User
Joined Jan 2012
19 Posts
I could add a lot, but some of my ideas I believe you have already seen on DIYDrones.
One item about the 80 pin is that, at the moment, there is only ONE chip select for SPI and data_ready pin for SPI. However, each device on an SPI bus must have a discrete CS and data_ready pin.
In addition, I think the designer is merely porting the PixHawk; it has six FMU PWM channels and eight IO PWM channels?!
I2C is a blocking protocol and should NOT be used on a flight controller! OK; one but NOT two!
That DF17 80 pin connector can only carry 300mA per pin. With two pins that's 600mA. "VDD 5V hipower" is a 1.5A line (in the PixHawk)!
twbrkfd1 is offline Find More Posts by twbrkfd1
Reply With Quote
Old Jul 02, 2015, 10:28 AM
mike_kelly is offline
Find More Posts by mike_kelly
Wisconsin
United States, WI, Hayward
Joined Jan 2012
1,674 Posts
Quote:
Originally Posted by twbrkfd1 View Post
I could add a lot, but some of my ideas I believe you have already seen on DIYDrones.
One item about the 80 pin is that, at the moment, there is only ONE chip select for SPI and data_ready pin for SPI. However, each device on an SPI bus must have a discrete CS and data_ready pin.
In addition, I think the designer is merely porting the PixHawk; it has six FMU PWM channels and eight IO PWM channels?!
I2C is a blocking protocol and should NOT be used on a flight controller! OK; one but NOT two!
That DF17 80 pin connector can only carry 300mA per pin. With two pins that's 600mA. "VDD 5V hipower" is a 1.5A line (in the PixHawk)!
Those are important points because an industry standard will never be accepted that is too limited for new designs.
mike_kelly is offline Find More Posts by mike_kelly
RCG Plus Member
Old Jul 02, 2015, 10:48 AM
Julez is online now
Find More Posts by Julez
Proud to eat Kraut ;-)
Julez's Avatar
Germany
Joined Dec 2003
5,605 Posts
Mike: Please don't take it personal, but could you explain to me why the 100% quote of the OP in the second posting should not be considered a waste of space?
Julez is online now Find More Posts by Julez
Reply With Quote
Old Jul 02, 2015, 11:42 AM
SamurAchzar is offline
Find More Posts by SamurAchzar
Registered User
Joined Jan 2009
1,829 Posts
Quote:
Originally Posted by Julez View Post
Mike: Please don't take it personal, but could you explain to me why the 100% quote of the OP in the second posting should not be considered a waste of space?
It definitely is.
SamurAchzar is offline Find More Posts by SamurAchzar
RCG Plus Member
Reply With Quote
Old Jul 02, 2015, 02:48 PM
twbrkfd1 is offline
Find More Posts by twbrkfd1
Registered User
Joined Jan 2012
19 Posts
crayfellow, MavLink in the ArduCopter provides a rich set of commands which can be sent by an upper level system controller (flight controller). I suspect this is how the main computer in the Solo is controlling the flight controller in the Solo.
twbrkfd1 is offline Find More Posts by twbrkfd1
Reply With Quote
Old Jul 02, 2015, 02:59 PM
twbrkfd1 is offline
Find More Posts by twbrkfd1
Registered User
Joined Jan 2012
19 Posts
Auvidea, I wouldn't get too hung up on that 80 pin connector. I don't see it in the Solo. Which means the "PixHawk 2" is NOT in the Solo. More pictures needed!
At this point the "pixHawk 2" is a 3DR initiative. Note that 3DR did NOT design the original PX4/PixHawk. It was a free collaboration. Until it is actually in production, schematics and 3D PCBs are just vaporware. Right now I can buy a PixRaptor from GoodLuckBuy for $109 so I'd say the "PixHawk 2" is moot.
However, for the future, a "bus" type design is of questionable value. Mainly because of the way the the components interact. Unlike a PC, there is no need for multi-wire bus type connections. MavLink (connection to higher level control computer) via serial port, GPS via serial port, servos/ESCs via 3pin, RC receiver via 3 pin. For faster interprocessor communication(between flight controller and higher level mission controller) SPI or CAN could be used instead of the 115kbaud serial port.
The original APM had it right with the connectors coming out the end of the board. The Pixhawk, with the connection out the top, creates a rats nest of unreliable wiring. The Pixhack and PixRaptor, and other upcoming clones remedy Pixhawk's wiring faults and IMU vibration mounting issue but propagate its other shortcomings.
twbrkfd1 is offline Find More Posts by twbrkfd1
Last edited by twbrkfd1; Jul 02, 2015 at 03:09 PM.
Reply With Quote
Old Jul 02, 2015, 04:33 PM
mike_kelly is offline
Find More Posts by mike_kelly
Wisconsin
United States, WI, Hayward
Joined Jan 2012
1,674 Posts
Although I agree 100% with your comments about the Pixhawk vs Pixraptor the OP is pondering carrier boards. I think the industry would benefit from a universal one.

Cheers

Happy Julez?
mike_kelly is offline Find More Posts by mike_kelly
RCG Plus Member
Old Jul 08, 2015, 07:25 AM
twbrkfd1 is offline
Find More Posts by twbrkfd1
Registered User
Joined Jan 2012
19 Posts
I made a mistake about new v7 ARM based microcontrollers. The Atmel SAME70 and SAMS70 use the v7 core with FPU and run up to 300MHZ. The STM32F7xx does not and only runs at 216MHZ.
I'm looking at using the Atmel chips only because of the development envirionment; Atmel Studio (crippled version of MS Visual Studio). In the long run, the real cost is software development.
Additionally, I saw the Solo interior and it has a Pixhawk 2; at least the first incarnation. The Pixhawk2 is hidden/encased in a black plastic cover, and somewhat sealed. It would have to be broken open to see the internals. It is mounted to a carrier(motherboard) using the 80 pin connector(DF17).
The system works by sending MavLink commands from the Solo's 1ghz CPU to the PixHawk2 over a serial port (DF17). Solo has a Atheros WiFi transceiver. As does the Solo controller.
Unbelievably, 2.4GHz WiFI in the ISM band and TCP/IP are being used by Solo as the "RC radio link" (old way:RC uses 2.4Ghz RF carrier in the ISM band to send PWM encoded in a PPM stream to an RC receiver which outputs the PPM to a PixHawk which decodes the PPM into discrete PWM; what a hack![real old way used PWM encoded on a carrier in the 72MHz RC band])
While the Solo scheme SEEMS to work OK, there are obvious negative issues with using WiFi for a real-time control link. In addition, it can be seen the PixHawk is strictly being used for a flight controller and gee-whiz camera related control features are being off-loaded to a "copter" main computer. In effect the PixHawk 2 is being relegated to AHRS and stabilization.
A simple carrier(or base mount) could be created to match the PixHawk 2 to have the motor/servo, serial port, RC receiver/PPM inputs, power connections, etc. in order to create a self contained Pixhawk2 flight controller. No doubt the makers are already on to it.
twbrkfd1 is offline Find More Posts by twbrkfd1
Reply With Quote
Old Jul 08, 2015, 07:36 AM
twbrkfd1 is offline
Find More Posts by twbrkfd1
Registered User
Joined Jan 2012
19 Posts
crayfellow, that's how the Solo is configured. PixHawk2 is just an AHRS.
twbrkfd1 is offline Find More Posts by twbrkfd1
Reply With Quote
Old Jul 15, 2015, 04:35 PM
ali.beygi1368 is offline
Find More Posts by ali.beygi1368
Registered User
Joined Jan 2015
19 Posts
As I can remember some users who are participating here was also participating in following discussion:
diydrones.com/forum/topics/pixhawk-vs-pixhawk-2
One of Tomas's comments about Pixhawk 2 flaws was deletet and he is banned from that website. Do you have a copy of that comment in your inbox?
ali.beygi1368 is offline Find More Posts by ali.beygi1368
Reply With Quote
Old Jul 15, 2015, 04:41 PM
crayfellow is offline
Find More Posts by crayfellow
Registered User
Joined May 2015
39 Posts
I have found that thread has been cleared as well, that is really troubling.

I personally really need some APM assistance on a unique rig and it's quite unfortunate 3DR has gone this route. I would like to throw my hat in the ring to help sponsor future advancement in this area via my company as it seems they are no longer well suited for the position based on their transition toward the DJI model.
crayfellow is offline Find More Posts by crayfellow
Reply With Quote


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion A little help with general design? Badot Foamies (Scratchbuilt) 16 Feb 18, 2015 10:53 PM
Help! Designing aircraft carrier/battle ship hybrid need help with design elements Toradore Scale Boats 58 Jul 05, 2013 05:47 PM
Discussion PIXHAWK pxIMU v.2.5 Open-Source IMU now available! pixhawk UAV - Unmanned Aerial Vehicles 4 Apr 30, 2011 03:47 AM