Discussions

LiDAR VLP 16 PUCK LITE from Velodyne and ublox M8N

Posted by Pedro Henrique R. P. B. Silva on January 13, 2017 at 3:44am

Hi,

Has anyone ever tried a setup where you have used an ublox M8N to connect to the LiDAR from Velodyne? I did all the wiring connections as you can see on my diagram. I got a PPS Locked on the LiDAR, but no GPS coordinates. 

Someone has already make it work?

Conectando GPS M8N ao LiDAR Velodyne.pdf

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Replies

  • Pedro Henrique R. P. B. Silva March 17, 2017 at 11:35am

    Yes, I used it, but I had no luck trying to create a map with it.

    I think that a GPS RTK would be perfect, but the VLP16 is extremely limited with the GPS it accepts in its Interface Box. So I think the best solution is to connect a simple GPS to the Lidar just to have it working as a clock. And then syncing the data with an external RTK.

    Rohan R Paleja said:


    Oh okay,

    have you tried to use the Veloview software? I think the GPS signal needs to be very accurate to create a precise map so a GPS with submeter accuracy could be used.
    Pedro Henrique R. P. B. Silva said:

    Hi, Rohan

    I managed to connect the GPS, but I couldn't map anything with precision. I still have no idea how to map an indoor area. For outdoor mapping, I sync the GPS and IMU data from a pixhawk fc with the LiDAR points, but there's no precision in the map.

    Rohan R Paleja said:

    Hi,

    I am attempting to do the same thing. So was the veloview program able to map your room or surroundings accurately as the lidar was moved?

  • Rohan R Paleja March 17, 2017 at 11:12am


    Oh okay,

    have you tried to use the Veloview software? I think the GPS signal needs to be very accurate to create a precise map so a GPS with submeter accuracy could be used.
    Pedro Henrique R. P. B. Silva said:

    Hi, Rohan

    I managed to connect the GPS, but I couldn't map anything with precision. I still have no idea how to map an indoor area. For outdoor mapping, I sync the GPS and IMU data from a pixhawk fc with the LiDAR points, but there's no precision in the map.

    Rohan R Paleja said:

    Hi,

    I am attempting to do the same thing. So was the veloview program able to map your room or surroundings accurately as the lidar was moved?

  • Pedro Henrique R. P. B. Silva March 17, 2017 at 11:02am

    Hi, Rohan

    I managed to connect the GPS, but I couldn't map anything with precision. I still have no idea how to map an indoor area. For outdoor mapping, I sync the GPS and IMU data from a pixhawk fc with the LiDAR points, but there's no precision in the map.

    Rohan R Paleja said:

    Hi,

    I am attempting to do the same thing. So was the veloview program able to map your room or surroundings accurately as the lidar was moved?

  • Rohan R Paleja March 17, 2017 at 10:43am

    Hi,

    I am attempting to do the same thing. So was the veloview program able to map your room or surroundings accurately as the lidar was moved?

  • Pedro Henrique R. P. B. Silva January 25, 2017 at 7:25am

    Hello, Matej

    After many tries, I could make it work.

    I had to do exactly as you said, reprogram the ublox using u-center and disabling every GNSS except GPS. I also had to access the pin 3 of ublox m8n to get the PPS.

    But besides that, I had to connect an inverter chip (7404) between the TX of the GPS and the RX of the LiDAR. I will send the configuration file and the connection diagram. It might help someone in the future.

    Thanks for your help!



    Matej Miljko said:

    Hi Pedro,

    I have no experience with this but after some google-fu I think this might be the answer:

    First I saw this in Velodyne's manual:

    The user must configure their GPS device to issue a once-a-second synchronization pulse (PPS, 0-5V, rising edge), typically output over a dedicated wire, and issue a once-a-second NMEA standard $GPRMC sentence. No other output message from the GPS will be accepted by the VLP-16.

    Did you do that? If not I think you should be able to do it in Ublox u-center software.

    You can connect the gps to program it using one of these methods.

    This thread might explain your problem.

    Or the gps had no lock.

    Best of luck

    Conectando GPS M8N ao LiDAR Velodyne(UPDATE).pdf

    Config_para_LiDAR_update.txt

  • Matej Miljko January 13, 2017 at 6:06am

    Hi Pedro,

    I have no experience with this but after some google-fu I think this might be the answer:

    First I saw this in Velodyne's manual:

    The user must configure their GPS device to issue a once-a-second synchronization pulse (PPS, 0-5V, rising edge), typically output over a dedicated wire, and issue a once-a-second NMEA standard $GPRMC sentence. No other output message from the GPS will be accepted by the VLP-16.

    Did you do that? If not I think you should be able to do it in Ublox u-center software.

    You can connect the gps to program it using one of these methods.

    This thread might explain your problem.

    Or the gps had no lock.

    Best of luck

    UBlox GPS Configuration — Copter documentation
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