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Thread: Reading XV-11 LIDAR Tx Serial Data

  1. Reading XV-11 LIDAR Tx Serial Data

    Hi all,
    I've got a Neato LIDAR (v2.6 I think but for sure at least v2.4) and have hooked it up to serial and I'm able to see the output. The data however is not as I would expect by looking at other some xv11 references on how the data should be being transmitted (mainly https://xv11hacking.wikispaces.com/LIDAR+Sensor). I'm trying to determine if I have a malfunctioning device. First: should I expect data to be transmitted as sooon as it's powered even without the motor powered on? Second: Even when I do spin it up the data I'm reading is sending no "0xFA" bytes at all (well, maybe one or two out of 1000's of bytes). My impression is that I should get 0xFA at the beginning of every 22 bytes transmitted. Basically, I'm trying to figure out what I could be doing incorrectly or if my LIDAR is not working, hence stop banging my head against the wall.
    Last edited by ttosi; 02-27-2015 at 06:14 PM.

  2. Re: Reading XV-11 LIDAR Tx Serial Data

    What is your connection setup?
    I have seen setups that corrupted the stream...
    ---
    Personal blog: http://xevel.org
    USB2AX documentation: http://xevelabs.com

  3. Re: Reading XV-11 LIDAR Tx Serial Data

    Thank you Xevel, my connection setup was exactly the problem. My ultimate goal is to dedicate an arduino to control the LIDAR so I was using LIDAR -> Arduino Nano SoftwareSerial -> Hardware Serial -> FTDI -> Laptop. My guess is the SoftwareSerial was the problem or maybe the Nano wasn't able to handle it. Now I've got it rigged from LIDAR -> RPi UART and using the PWM pin and a TIP120 to control the rotation speed. I'm now getting output I'd expect (although I haven't analyzed the distance measurements yet, just the index and RPM). My question now is, what is the ideal RPM to spin at?

    Thank you again
    Tony

  4. Re: Reading XV-11 LIDAR Tx Serial Data

    Glad you could fix that. Soft serial is bad for "fast" serial (anythong above 19200 I would try to avoid unless I am sure nothing else will ever be done by this board).
    However, even going from a hardware serial on ( for example an Arduino Mega) to another hardware serial, with the arduino software, is not a great idea...

    300 rpm is nice, you should try something like that. Depending on the time it takes you to process each sample, you might want to slow that down. Going too high will result in every other sample being discarded (cf lidar wiki you pointed to).
    ---
    Personal blog: http://xevel.org
    USB2AX documentation: http://xevelabs.com

  5. Re: Reading XV-11 LIDAR Tx Serial Data

    Yeah, learned that the hard way but really happy it's not a defective unit. I'm now getting appropriate distance measurements spinning it at ~295rpm. Good advice to not even go hardware to hardware serial. Will probably use SPI or I2C to output the scrubbed data to my RPi 2. Thank you once again!

    TT

  6. Re: Reading XV-11 LIDAR Tx Serial Data

    Given the timing of the data (it's a relatively slow feed with info on what data sample goes where, making real-time processing unnecessary), you could also easily use a usb to serial chip, even the cheapest one would do the job.
    For my robots I designed a board (USB2LDS) that takes care of the that and speed control with the same chip. Simplifies connecting everything together.
    ---
    Personal blog: http://xevel.org
    USB2AX documentation: http://xevelabs.com

  7. Re: Reading XV-11 LIDAR Tx Serial Data

    Wow, that is pretty awesome. But if used that then that'd take away all of my fun (and learning) :-)

    I have an ESP-8266 ESP-01 and I decided I'm going to use that to stream the serial data over wifi (hopefully). My goal is to have this on a robot and this way I can stream directly to a laptop and process the data there, relaying back any drive control commands to the RPi on the bot. This'd free up the Rpi for other stuff.

  8. Re: Reading XV-11 LIDAR Tx Serial Data

    Nice idea Have fun!
    ---
    Personal blog: http://xevel.org
    USB2AX documentation: http://xevelabs.com

  9. Re: Reading XV-11 LIDAR Tx Serial Data

    I have XV-11 v2.6. Using Win7 serial port and RealTerm (115200 N81), when I spin the rotor I get all zeros except for a periodic Piccolo Laser message. To read the ASCII code correctly I have to shift it by 255 and divide by 2. Do I have a serial hardware or setup problem? Any suggestions would be appreciated.

  10. Re: Reading XV-11 LIDAR Tx Serial Data

    Might be late, but to me it looks like you have power problems. THe "Piccolo Laser" message is what the sensor sends when it boots, so if you get it multiple times it means your sensor is rebooting. This could happen if you power it from a source that cannot sustain the power draw, or is instable.
    Try with a reliable power supply, and make sure the rotor spins fast enough for it to give good readings (it will only give valid readings between 180 and 349 RPM).
    ---
    Personal blog: http://xevel.org
    USB2AX documentation: http://xevelabs.com

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