Lidar Lite v3 HP RPi3 b+ strange behavior

[Matu37]

Hi All

I have a setup that combines of LLV3HP and RPi3b+ with Rasbian stretch. I’m using a standalone PSU with 2.5A@ 5V. The problem is that everything works fine, but once or twice in a month the sensor stops and returns only 0. Then I have to keep the system off power for about 5 minutes and then it starts again. If I just reboot or keep it off power for 10 seconds it will not start.

Any ideas?

[scharette]

Hi Matu37,

Seems like a weird situation. My first guess would be that the LLV3HP’s internal state becomes incoherent and it thus stops responding and needs to be power cycled.

Have you tried modifying your code to detect those instances (i.e.: a “long” string of 0s) and then send a “reset” command to the LLV3HP and see if that helps? Of course, if you changed any settings they would need to be changed again.
See page 8 of the datasheet for details (register 0x00).

Also, is the device in an enclosed space? Maybe it is simply overheating / needs time to cool down? This would also explain why it can’t just be quickly power cycled (and needs minutes before it’ll work again).

In the meantime I have contacted the manufacturer to see if they have any other troubleshooting ideas. I’ll post here again once I have more information.

Sincerely,

[scharette]

@Matu37

Then I have to keep the system off power for about 5 minutes and then it starts again. If I just reboot or keep it off power for 10 seconds it will not start.

Here’s what the manufacturer has to say about that:

@Manufacturer

Even if it were getting hot there should be no issue rebooting within 10 seconds. It should only take less than a second to reset. These sensors can operate at relatively high temperatures, I’m not sure that’s the real issue.

Concerning I2C issues, here are more details:

@Manufacturer

It may more likely be an issue with the I2C communications. We know that, at times, there have been issues with the communications drivers of the RPi and how they function with the LL sensors. Any glitch in the I2C communications can cause either the RPi or the sensor to lock up. Without knowing exactly how it’s being operated it’s hard to know what the cause might be, but that would be my first guess.

When you have these crashes do you power cycle both the RPi and sensor or the sensor only? It seems likely that in such a case the issue would be with the RPi I2C, not the sensors. The manufacturer further proposes the following:

@Manufacturer

If they try a soft reset and it doesn’t respond that would be a big indicator that the I2C comms has failed. I also suspect the delay in responding to a power cycle or reboot may be related to I2C not necessarily the sensor. It might take a while for the RPi to reestablish communications if there’s been an I2C failure. Have they tried resetting the RPi after the sensor has been restarted?

Also, to help with the setup you may want to try the following:

@Manufacturer

I would suggest using the power enable line to power cycle the sensor when this happens if a soft reset doesn’t work. I would also have them look at the system status registers and see if they can read them. Again, if they can’t, they’ve lost communications.

[Matu37]

Hi

Thank you for taking the time to elaborate on the matter. The truth is I don’t have 1 sensor that act’s that way, i have 9.
First thing I do before setting any filter options is writing 0x00 to 0x00 (can’t find a way to post a picture of the C++ code). The power delivery is via line interactive ups, then a Meanwell 2.5 A 5V PSU set @ 5.1Vout. Due to the fact it’s an industrial region, the power can fluctuate on the 220V mains! Also checked syslog of RPI, no indication of under voltage.
I have tried voltage drop until 3.3V in the lab to get a similar problem, but that is not the case. Love the device, but this issue is causing a lot of trouble. Can it be a voltage peak on 220V mains?