Page 4 of 20 FirstFirst 1234567814 ... LastLast
Results 31 to 40 of 197

Thread: The Open Lidar Project - Hack the Neato XV-11 Lidar for a $200 Bounty!

  1. #31
    Join Date
    Dec 2007
    Location
    Portland, OR
    Posts
    3,198
    Images
    952
    Rep Power
    141

    Re: A question about Arbotix python library

    Mon 11/22/2010 9:34 PM
    tmig has just posted


    I don"t think the sensor has that much resolution... they talk about an error inferior to 3cm at 600cm, that's <0.5%. what would possibly be the use of using more bits for coding the distance than what can be mesured ?

    Laziness?

    In my experience, having worked on too many lines of legacy code for oceanographic instrumentation, this is an all too common practice. They do not need to store the data so they don't need to compact it for efficiency, and thier internal calculations may warrrant using a 32 bits to avoid overflow. Of course that doesn't mean I am correct either.

    Initially I considered floating point formats, but was not successful in overlaying one on this data.

  2. #32
    Join Date
    Dec 2007
    Location
    Portland, OR
    Posts
    3,198
    Images
    952
    Rep Power
    141

    Re: A question about Arbotix python library

    Mon 11/22/2010 9:37 PM
    Xevel has just posted


    My guess for the rest of the data is that it's either some kind of timing information (time elapsed between two samples), or something about he quality of the measure. Or both. I don't really believe they would encode the distance on 32 bits on a device where the noise level is around 0.5% of the total range...

  3. #33
    Join Date
    Dec 2007
    Location
    Portland, OR
    Posts
    3,198
    Images
    952
    Rep Power
    141

    Re: A question about Arbotix python library

    Mon 11/22/2010 9:51 PM
    Hash79 has just posted



    Considering the DSP handles data in 32bit easily, and other than the start location marker which would need to be coded in the serial stream it seems nothing else other than distance would need to be transmitted.

    I would agree with the 32 bit data just because it seems easiest and quickest to take the raw computed data from the DSP and dump it serially and let the next system deal with the data. That sensor does not need to send any other data besides distance. Location is easily determined by how far from the start marker you are.

    -Hash

  4. #34
    Join Date
    Dec 2007
    Location
    Portland, OR
    Posts
    3,198
    Images
    952
    Rep Power
    141

    Re: A question about Arbotix python library

    Mon 11/22/2010 11:01 PM
    shimniok has just posted


    FWIW I am heading along the same path with the protocol/data from Sparkfun. It wouldn't surprise me to learn they are throwing 32 bits of data per reading across the wire, although the white paper talks about sending only 2 bytes per measurement. 32 bits x 360 degrees = 11520 bits per sweep. The thing sweeps 10 times per sec = 115200 bps. Hmm...

  5. #35
    Join Date
    Dec 2007
    Location
    Portland, OR
    Posts
    3,198
    Images
    952
    Rep Power
    141

    Re: A question about Arbotix python library

    Mon 11/22/2010 11:13 PM
    Hash79 has just posted



    Well my XV-11 arrives at my house tomorrow and I get back home Wednesday evening. I wish I wasn't traveling for work right now or I would be digging into this thing! I'm jealous of Xevel right now, hacking away with his!

    All i have are the Sparkfun dumps as well and considering the rudimentary dumps they have provided perhaps Xevel could provide some more useful dumps in a realistic constrained environment. Say a 2ft x 2ft box or something like that. If the thing isn't totally hacked by Thursday hopefully I can contribute to the effort!

    Xevel, have you tried transmitting any data to the module? Does it respond when you send ASCII chars to it after boot, say a "?" or anything like that? The terminal output shown on Sparkfun has a # at the bottom like the module is waiting for an input. I would bet there are setup modes in there for production staff to calibrate and test the module.

    -Hash

  6. #36
    Join Date
    Dec 2007
    Location
    Portland, OR
    Posts
    3,198
    Images
    952
    Rep Power
    141

    Re: A question about Arbotix python library

    Mon 11/22/2010 11:19 PM
    Nammo has just posted


    Quote Originally Posted by tmig
    Laziness?

    In my experience, having worked on too many lines of legacy code for oceanographic instrumentation, this is an all too common practice.

    Be nice... people from Neato are reading this thread.

    - Nammo

  7. #37
    Join Date
    Dec 2007
    Location
    Portland, OR
    Posts
    3,198
    Images
    952
    Rep Power
    141

    Re: A question about Arbotix python library

    Mon 11/22/2010 11:23 PM
    Nammo has just posted


    Quote Originally Posted by shimniok
    FWIW I am heading along the same path with the protocol/data from Sparkfun. It wouldn't surprise me to learn they are throwing 32 bits of data per reading across the wire, although the white paper talks about sending only 2 bytes per measurement. 32 bits x 360 degrees = 11520 bits per sweep. The thing sweeps 10 times per sec = 115200 bps. Hmm...

    From the SparkFun logical analyzer screenshot, it's an 8n1 serial UART. That means you really only have 92160 bits to play with. You can see there are delays between each 32-bit data burst so they're not even using the whole channel.

    - Nammo

  8. #38
    Join Date
    Dec 2007
    Location
    Portland, OR
    Posts
    3,198
    Images
    952
    Rep Power
    141

    Re: The Open Lidar Project - Hack the Neato XV-11 Lidar for a $200 Bounty!

    Mon 11/22/2010 11:37 PM
    Xevel has just posted


    Quote Originally Posted by Hash79
    Well my XV-11 arrives at my house tomorrow and I get back home Wednesday evening. I wish I wasn't traveling for work right now or I would be digging into this thing! I'm jealous of Xevel right now, hacking away with his!

    All i have are the Sparkfun dumps as well and considering the rudimentary dumps they have provided perhaps Xevel could provide some more useful dumps in a realistic constrained environment. Say a 2ft x 2ft box or something like that. If the thing isn't totally hacked by Thursday hopefully I can contribute to the effort!

    Xevel, have you tried transmitting any data to the module? Does it respond when you send ASCII chars to it after boot, say a "?" or anything like that? The terminal output shown on Sparkfun has a # at the bottom like the module is waiting for an input. I would bet there are setup modes in there for production staff to calibrate and test the module.
    -Hash
    I don't know what made you think I have the robot... I just worked from the Sparkfun dumps. And I might not be able to get one before the international release anyway... so I'm the one who should be jealous

    By the way, continuing my tests (after 2 hours of sleep ^^"), I still don't see how the "big unsigned int" theory could work. The bits 6 and 7 of X+1 seems to me like they are flags. When X+1:7 is set, the data looks good, and when it is not, it looks like crap... But for X+1:6, I have no idea...

    X+1:5 and X+1:4 are never set on the data I work with (a subset of less than 1 second of the NoShield Sparkfun dump).

    Here is a plot where :
    X+1:7 is set => Red
    X+1:6 is set => Green
    none of X+1:6 nor X+1:7 are set => Blue.
    (on the data set I have, these are disjointed groups)
    (http://forums.trossenrobotics.com/ga...original=1&c=3)

  9. #39
    Join Date
    Dec 2007
    Location
    Portland, OR
    Posts
    3,198
    Images
    952
    Rep Power
    141

    Re: The Open Lidar Project - Hack the Neato XV-11 Lidar for a $200 Bounty!

    Mon 11/22/2010 11:42 PM
    Nammo has just posted


    Quote Originally Posted by Xevel
    I don't know what made you think I have the robot... I just worked from the Sparkfun dumps.

    Somebody ought to send you a robot! Maybe SparkFun will get tired of their unit with the voided warranty...

    - Nammo

  10. #40
    Join Date
    Dec 2007
    Location
    Portland, OR
    Posts
    3,198
    Images
    952
    Rep Power
    141

    Re: The Open Lidar Project - Hack the Neato XV-11 Lidar for a $200 Bounty!

    Mon 11/22/2010 11:54 PM
    Xevel has just posted


    I'm all for it
    My home is like a shelter for robots out of warranty xD

Thread Information

Users Browsing this Thread

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

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
  •