Results 1 to 8 of 8

Thread: Pololu's Wixel + Arbotix Commander V2

  1. #1
    Join Date
    Jun 2011
    Location
    USA
    Posts
    539
    Images
    107
    Rep Power
    39

    Pololu's Wixel + Arbotix Commander V2

    For a project I just started, the Wixel MCU from Pololu seems to be sufficient for what I need (namely: 1 UART for Dynamixel servos, and a wireless serial connection).

    I figured I'd use my Arbotix Commander for the controller. Since the Wixel's use some custom hardware wireless communication method, I need two of them (and I bought two of them for $20 total on Black Friday); one on the bot, and one to forwards the commands from the Arbotix.

    I used some of the spare connections on the Seeeduino that is part of the Arbotix Commander V2, wired these to some female headers on a chunk of perf board, and stuck stuff together with double sided foam tape.

    I first verified that the Wixel forwards the Arbotix Commander signals with the USB-to-Serial App that Pololu provides. And I've now succeeded with using the Wireless Serial App on both Wixels so that Arbotix Commander signals are sent to a PuTTY terminal on my computer. Not to be a shill, but that was easier to set up than any MCU + Xbee configuration I've seen.

    And pictures: (Click to embiggen)
    Click image for larger version. 

Name:	wixelcommander01_original.jpg 
Views:	1077 
Size:	122.2 KB 
ID:	4064
    Click image for larger version. 

Name:	wixelcommander02_original.jpg 
Views:	1111 
Size:	75.8 KB 
ID:	4065Click image for larger version. 

Name:	wixelcommander03.jpg 
Views:	1042 
Size:	84.8 KB 
ID:	4066
    Last edited by Gertlex; 07-01-2012 at 01:52 AM.

  2. #2
    Join Date
    Jun 2011
    Location
    USA
    Posts
    539
    Images
    107
    Rep Power
    39

    Re: Pololu's Wixel + Arbotix Commander V2

    A modified app for the Wixel now compiles with the Commander code included. This is useful for the Wixel that is listening to the one plugged into the Commander.

    Non-clean code can be found in my fork of the wixel-sdk repository. All I've done is copy the code I used for Numa + Commander, and comment out stuff I'm not using, and re-arrange .h/.c files a bit. The relevant app is in apps/wireless_serial_twitch. https://github.com/erelson/wixel-sdk

    Had to skip the UART's buffer flushing after each complete Commander packet since there doesn't appear to be a comparable function in the Wixel libraries. (If I'm feeling like it, I might ask on the Pololu forums at some point...)

  3. #3
    Join Date
    Jun 2011
    Location
    USA
    Posts
    539
    Images
    107
    Rep Power
    39

    Re: Pololu's Wixel + Arbotix Commander V2

    I realized that with the Wixel on my Arbotix commander, if instead of forwarding the bytes generated by the commander, I instead forwarded the bytes received by the commander's xbee (i.e. from the robot), then I can hook a paired Wixel to my computer and get e.g. temperature information from the servos.

    To preserve the ability to use the Arbotix Commander to drive my Twitch robot (which uses the Wixel for control), I added some header pins and two jumpers (plus a cheat sheet). Switching between usecases just requires some pliers or small fingers.
    Click image for larger version. 

Name:	ArbotixCommanderWixelModeJumpers.jpg 
Views:	81 
Size:	61.8 KB 
ID:	7509

  4. #4

    Re: Pololu's Wixel + Arbotix Commander V2

    Award: Best thread necro :-)

  5. #5
    Join Date
    Jun 2011
    Location
    USA
    Posts
    539
    Images
    107
    Rep Power
    39

    Re: Pololu's Wixel + Arbotix Commander V2

    I should also document the 3d-print encapsulated switch wired to one of the push buttons, giving me the ability to set a mode. E.g. TwitchMX's turret mode + laser was toggled in this manner

  6. #6
    Join Date
    Jun 2011
    Location
    USA
    Posts
    539
    Images
    107
    Rep Power
    39

    Re: Pololu's Wixel + Arbotix Commander V2

    At Maker Faire 2019, I had Numa 2 sending temperature information back over the Xbee. I had my added-on Wixel in turn relaying that to my computer. The goal here was to be able to monitor temperatures while moving the robot, but setting up a computer just to display that is tedious... and given that it's ultimately more useful during testing than during matches, reducing the friction of this realtime monitoring of temperatures better ensures I'll actually use this capability as I refine Numa 2.

    So, I threw on a 64x48 pixel OLED display that I got years ago from sparkfun. It's controlled via SPI with the Wixel. Thanks to Oestoidea's implementation, it was pretty straight-forward to get the display working for a simple "rotate through rows of an array and display (only) numbers" usecase. (After spending several days banging my head against a wall before noticing issues with integer overflow and unsigned integer math...)

    Click image for larger version. 

Name:	IMG_20190615_100842.jpg 
Views:	25 
Size:	76.3 KB 
ID:	7570

    Now I can finally finish up my write-up of Numa 2...

    And though no one should use it, the wixel side code lives here.

  7. #7

    Re: Pololu's Wixel + Arbotix Commander V2

    I tried doing exactly this (with a slightly different OLED) with an Arbotix Commander and a PhantomX quad, but the Xbee turn-around time latency made the Phantom way too jerky in its control. (I've never managed to use an Xbee in duplex mode without at least 200 ms dead time each time it decides to send data the other way.)
    Are you using the Wixel one way, and the Xbee the other? That seems to avoid this kind of problem!

  8. #8
    Join Date
    Jun 2011
    Location
    USA
    Posts
    539
    Images
    107
    Rep Power
    39

    Re: Pololu's Wixel + Arbotix Commander V2

    It's bidirectional via xbee. My data rate from the robot is to send one row of data (12 bytes) every 4s or so. I'm actually doing a single read of a single servo's temperature once per second, and sending data when I've updated all four values. Definitely an overabundance of caution against interferring with other things.

    Certainly the arduino could be driving the display, but my life is made easier by only maintaining build environs for micropython and SDCC (wixel), and not including Arduino

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Quick question on Arbotix Commander Version 2 - if anyone else had any issues
    By cdraptor in forum Humanoids, Walkers & Crawlers
    Replies: 8
    Last Post: 08-01-2013, 10:16 PM
  2. Arbotix 0.5.0
    By lnxfergy in forum ROS - Robot Operating System
    Replies: 17
    Last Post: 08-13-2012, 10:51 AM
  3. Project Robot Commander Pro
    By MarkosR in forum Project Showcase
    Replies: 0
    Last Post: 02-05-2012, 11:13 PM
  4. Question(s) Controlling Dynamixel with Arbotix Commander
    By Buell24 in forum Software and Programming
    Replies: 9
    Last Post: 01-04-2011, 12:47 PM
  5. Question(s) Arbotix Commander
    By elaughlin in forum Robotics General Discussion
    Replies: 2
    Last Post: 10-24-2010, 12:33 AM

Posting Permissions

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