Page 2 of 7 FirstFirst 123456 ... LastLast
Results 11 to 20 of 63

Thread: Next steps with a PhantomX AX Hexapod Mark II & BBB

  1. Re: Next steps with a PhantomX AX Hexapod Mark II & BBB

    Looking at the notes, I'm assuming the USB2AX firmware needs to be changed? Is this to the firmware in the usb2ax repository?
    Yes, you need to change the firmware. I guess the sources are somewhere in the extensive list of wonderful projects that is Kurt's Github. I haven't checked again when the fork happened but it's possible that his firmware does not support automatic rebooting in bootloader mode (like the main USB2AX firmware does). It's not a problem in itself as you can always run the bootloader (to put another custom firmware or the original one) by shorting a few pads together on the USB2AX, as explained here.

    Maybe I should finally integrate KurtEck's work into the main repo...
    ---
    Personal blog: http://xevel.org
    USB2AX documentation: http://xevelabs.com

  2. #12

    Re: Next steps with a PhantomX AX Hexapod Mark II & BBB

    Thanks, but I am pretty sure there are many boards I have not tinkered with (yet)

    As for USB2AX, have gone both ways, just think it is nice to offload more of the stuff too it, like having to call it N times per second to update each of the servos.

    But there are alternative ways as well. That is instead of interpolating N times per second, could instead try to run the gait/IK code N times per second and then have it move in very small increments. I think KevinO's newer stuff is more in that category.

  3. #13
    Join Date
    Jul 2014
    Location
    New Zealand
    Posts
    70
    Images
    3
    Rep Power
    19

    Re: Next steps with a PhantomX AX Hexapod Mark II & BBB

    Thanks both for your helpful advice.

    I'm in Japan for the next three weeks, so no build time but plenty of opportunity to read up on the options, put together a plan and wait for the latest parts order to arrive.

    Heading into winter here, so will be a good excuse to stay inside and work on the Phantom X.

    The summer project is now fully operational> http://gadgetblog.robotbits.co.nz/?p=63 , so will be fully focused on the robot build when I get back.

  4. #14
    Join Date
    Jul 2014
    Location
    New Zealand
    Posts
    70
    Images
    3
    Rep Power
    19

    Re: Next steps with a PhantomX AX Hexapod Mark II & BBB

    A bit of an update - I finally had a free Saturday to tinker with the Hexapod.

    I decided to leave the Arbotix-M in place and connected it to a Pi2 I picked up on my travels via a serial connection using the Pi GPIO pins, with a logic level converter to shift from 5v to 3.3v. Using a modified version of Kurt's Phoenix Input Commander code, the bot is at least taking basic instructions from the Pi. The fiddliest bit was getting the data transmitted to translate to the correct data type on the Arbotix.

    My latest hurdle though is that it only works if I manually press the reset button on the Arbotix-M after I've started the Pi script (Python). I'm assuming this is somehow related to the a required refreshing of the serial link.

    Any thoughts on how to avoid this and/or how to set up a remote reset for the Arbotix-M would be appreciated.

    Next step is to add the IR sensors and compass module.

  5. #15

    Re: Next steps with a PhantomX AX Hexapod Mark II & BBB

    Sounds interesting

    Hard to say what is going on, without looking at the code. I have not tried running the Arbotix-M with a Linux board installed. All of my current Linux versions (for Ax Servos), use something like an USB2AX device to talk to the servos. I will probably also see more about supporting the Arbotix-Pro, once I have more information (I do have one now for the HR-OS1). I also plan to have a version that uses a Teensy (3.1 or LC), to emulate and extend the USB2AX.

    My assumption is that you are using a USART on the RPI2 to talk to the Arbotix-M and you have it connected to the USART on the Arbotix-M.. In theory the Arbotix code base would not have to change as you can simply send it the same packets as the Commander does.

    As for why it is hanging until you hit reset? good question. If it were me, I would probably instrument the code with digitalWrites and the like and hook up Logic Analyzer to get an idea where the code is.

    In addition, I would have the Arbotix output debug messages over the Serial port back to the RPI2 and setup code on the RPI2, that when it receives something it writes it back out to stdout... That way you can also print out stuff. I have this setup already in my Phantom Phoenix code base with a Visual Basic program, where I put the computer between the Commander and the Arbotix (usually leave XBee in Arbotix, remove XBee from commander, put that XBee on a USB XBee adapter, connected up to PC and also plug commander (USB) into PC. Program allows you to select the two comm ports. Anything received from Commander is echoed to the XBee one, anything from the XBee side is displayed in a listbox that is part of the program...

    Reset: I have not looked at this in a long time, but my recollection is that a program can reboot, by doing something like JMP 0. So you could hookup another IO pin between RPI2 and Arbotix. Couple of options here, could either connect to standard IO pin on Arbotix, that you use to set a state. I would probably hook up either an external Pull-Up or Pull-Down resistor so it has a known state, and the RPI2 sets it to another state, which is detected by the program on Arbotix-M, which when it detects it resets...

    Or use an the RPI2 pin to connect to one of the Reset pins of the Arbotix-M. From the schematic: http://learn.trossenrobotics.com/ima...-schematic.pdf I believe the reset line has an external 10K PU resistor on it. You can use either the reset pin that is on the FTDI connector or on the ISP connector. Again I have not tried this, so you would need to experiment.

    Hope that helps
    Kurt

  6. #16
    Join Date
    Jul 2014
    Location
    New Zealand
    Posts
    70
    Images
    3
    Rep Power
    19

    Re: Next steps with a PhantomX AX Hexapod Mark II & BBB

    Thanks for the hints.

    I did have a quick look at running the RPi2 with a USB2AX (I ordered one a while back to experiment with) but got a bit lost on the code needed to run that configuration, so for my first attempt started with what I already knew.

    Where I got lost with the USB2AX was around the firmware updates required to get the USB2AX operating with the RPi code in the Github.

    I haven't had much time to progress today, but loaded my very WIP code onto GITHUB https://github.com/CreedyNZ/Hexapod_...ix/tree/master just in case anyone is interested. One other trap that caught me out is that the left and right joystick variables in the base Input Controller code I used to modify appear to be the reverse of the joysticks when actually using the joysticks with the Commander EX code.

    I've been teaching myself Python with the help of Professor Google, so the code may not be pretty, but works, mainly anyway.
    Last edited by CreedyNZ; 04-26-2015 at 05:46 AM.

  7. #17
    Join Date
    Jul 2014
    Location
    New Zealand
    Posts
    70
    Images
    3
    Rep Power
    19

    Re: Next steps with a PhantomX AX Hexapod Mark II & BBB

    Bit of a setback today. Was putting "Jim-Bob", the name my children have decided to call the Hexapod, back together after installing IR distance sensors, camera, ultrasonic sensor and some NeoPixels for bling. I stupidly dropped the powerdrill and cracked the bottom body plate in two.

    Hopefully I can get a replacement shortly and get the project back on track.

  8. #18
    Join Date
    Jul 2014
    Location
    New Zealand
    Posts
    70
    Images
    3
    Rep Power
    19

    Re: Next steps with a PhantomX AX Hexapod Mark II & BBB

    Jim-Bob is now happily wandering the house, though somewhat aimlessly, without crashing into things and is making good use of the Phoenix translate functions to produce interesting gestures when approached or approaching something.

    The Arbotix-M is handling the movement, running a modified version of Kurt's Phoenix code, while the RPI2 is providing the directional commands to the Arbotix-M via a serial connection. An ultrasonic and four Sharp IR sensors provide the obstacle detection.

    This now begs the next question of where to next?

    I'm very impressed by the work of r3n33 & KevinO et al in developing ROS enabled Hexapods and so I've installed ROS on the RPI2 and have been working through the tutorials. One thing that has become apparent is my lack of a decent understanding of how the kinematics actually works (apart from reading the excellent Phoenix code), so would like to try and put a basic kinematic engine together to better understand what's going on.

    Any suggestions on a good place to start learning Hexapod kinematics? My many Google searches have been a bit overwhelming!

  9. #19
    Join Date
    Apr 2013
    Location
    Boston, MA
    Posts
    260
    Images
    11
    Rep Power
    29

    Re: Next steps with a PhantomX AX Hexapod Mark II & BBB

    Nice work so far. I have a couple of tidbits:

    The Linux based SBCs seem plenty capable of running real time kinematics. My code runs at a "frame rate" of 50hz and is processing body and leg trajectory and IK at every frame. It uses like 8% CPU resources

    I have some FK/IK basics on my blog if you dig around here:
    http://www.projectsofdan.com/?cat=4
    http://www.projectsofdan.com/?p=32


    I'm also really interested I kinematics which is what drove me to try and write it all myself to gain a better understanding. I've been on a robot hiatus for about a year, but I want to get back to improving my kinematics engine with more life-like movements/transitions and terrain adaption.

    Regarding architecture of this whole thing, I go back and forth a bit too and have wondered about putting the Arbotix back in and running my laptop as the real brain. On the other hand, having some horsepower on board is better for machine vision stuff which i'll get into sooner or later. I think you can spin your wheels planning forever, so I'm going to stick with this (RPi2) until I hit a real road block and worry about it then.
    Last edited by TXBDan; 06-17-2015 at 07:52 AM.

  10. #20
    Join Date
    Jul 2014
    Location
    New Zealand
    Posts
    70
    Images
    3
    Rep Power
    19

    Re: Next steps with a PhantomX AX Hexapod Mark II & BBB

    Thanks Dan,

    I took a look through your great explanations of the code and it certainly helped the understanding. Keen to have a go now and experiment myself when I return home from another work trip (air-travel, hotels and robot building don't mix well unfortunately!)

    Looking at your hardware setup for the RPi, the compactness of your setup looks great, but I had a couple of questions:
    I've been powering my RPi via the USB port, but it looks like you're backpowering directly to the GPIO pins?? I'd been reluctant to do that, even though it would tidy up the cables after reading commentary like this: https://github.com/raspberrypi/hats/...j8-gpio-header. I'm assuming it's all working OK for you though?
    is the Murata OKI-78SR-5/1.5-W36H-C 5V Switching Regulator at 1.5A enough for the RPi2?, again I assume it's working OK? I've gone way bigger with a 5A 25w supply, but finding it a bit bulky.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Question(s) PhantomX AX Hexapod Mark II Kit to Quadruped?
    By siempre.aprendiendo in forum Humanoids, Walkers & Crawlers
    Replies: 3
    Last Post: 04-23-2014, 11:34 AM
  2. News/Announcement PhantomX AX Hexapod Mark II Kit
    By etwx in forum Garage Sale
    Replies: 2
    Last Post: 04-08-2014, 08:31 PM
  3. Wanted: PhantomX Hexapod Mark I
    By fostac in forum Garage Sale
    Replies: 2
    Last Post: 01-03-2014, 12:21 AM
  4. Question(s) Quadruped Mark II PhantomX Robot Turret
    By hwan we in forum Humanoids, Walkers & Crawlers
    Replies: 1
    Last Post: 03-16-2013, 07:35 PM
  5. Question(s) PhantomX AX Quadruped Mark II PhantomX Robot Turret Equipped??
    By hwan we in forum Robotics General Discussion
    Replies: 1
    Last Post: 03-11-2013, 02:09 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •