RPlidar S2 - Can’t get it to work reliably from Python programs

Help & Support Robot Parts
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Dear all,

right now I have a hard time to operate my RPLidar S2 from Python. I tried two libs but they are not stable for one major reason I found out when I tried to write my own lib: The SLAMTEC protocol doesn’t give you any chance to sync again if a transmission error (loosing a byte or so) occurs, no safe sync marker.

I am not able to read a whole scan sweep w/o problems!

The SLAMTEC documentation on one hand seems to be outdated. For instance, nowhere I could find, that the S2 communicates with 1MBaud instead of the 115400 as set as default in all libs.

OTOH on https://github.com/Slamtec/rplidar_sdk they advertise a completely different (and new?) protocol. But that does not work at all.

What I wonder now is: Is there anyone operating an RPLidar S2 (on a Raspberry Pi) from Python? Which lib do you use? What’s your experiences? Any hints or pointers to additional, helpful dox?

Best regards
poseidon62

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Hi, have you seen this adafruit document? Overview | Using the Slamtec RPLIDAR on a Raspberry Pi | Adafruit Learning System

1 Like
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Tanks for the pointer, but the problems are the same here: After roughly 400 scans I get a RPLidarExcpetion( “Wrong body size”). If I try to proceed by issuing iter_scan() again, the software is not able to recover, the error persists. No surprise to me: When a byte is dropped, all the bytes to come are shifted by 1 byte and the software is not able to understand the data stream.

Now, I could do a reset, that stops the motor and then restarts it when issuing a iter_scan() again. But honestly: Stopping and starting the motor because a of a glitch in the transmission?

How do others do here?

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Hi,

I had the same problem with python.
So I developped an c++ shared library, and I use it in my python script.
It’s working well.