we are facing the exact same problem as seen here, just with a slight difference: the DC port stop working since we plugged in our mini barrel connector.
We need the lidar for a competition starting in a week, thus attempting the second option: powered USB port. However, so far without success:
We are using a rapsberry pi3 (erle brain) and rplidar A2 over the adaptor board(the mini usb port luckily still working), and a 3s 5200mAh battery.
We also got power module that supplies up to 3 A.
What we tried so far:
directly power the rplidar with cable and usb to rapspi3 --> switched to usb powering only
solder micro USB cable parallel to both rapsberry pi 3 and the power module output --> didn’t work
Could you give a short explanation of how it would work? we are quite desperate here… It’s on a quadcopter, so lighter solution is preferred.
We found out the problem. Now we split the power cable from the usb to be also connect to the battery. And only if the power is connected first, and the usb is connected to raspberry pi after the pi is booted, the adaptor board will start to draw current from the external power source while keep communication with the pi up and running.
Advice: do not break the mini barrel ! Designed for 5.5 V only.
Please note that the RPLidar A2 needs a very stable, 5 V DC power source that can provide up-to 1500 mA (see the specifications here).
If their is too many ripples in the power source’s voltage or if it cannot provide the appropriate current (especially during initialization), then the device may not work properly and return wrong data or no data at all.
Your situation is most likely due to the fact that the adapter board tries to draw power from the USB port directly as soon as it is powered. Since the RPi 3 cannot provide enough power by USB to properly initialize the RPLidar A2, it is started improperly (crashes) and when the battery power is added, it is already too late. The solution would be to always provide enough power to the RPLidar A2 before connecting the USB cable.
One way to implement this would be to replace the adapter board provided for development with a proper interface that does not power the device from USB power.
