The working range of the PMW3901 is 80mm to infinity, as it was (to my understanding) designed for use with flying drones. So it's fine on a Mars rover or other robot that's at least 80mm from the ground, but can't be used any closer than that. But flipping them to look at the ceiling won't work either, as they are effectively a low-resolution camera that relies on detail in order to determine movement, and most ceilings have little to no detail, just an expanse of white paint. I lobbied Pimoroni to consider implementing a sister sensor, the ST PAA5100JE, which is almost identical to the PMW3901 except its operating range was designed for something like a robot vacuum, 15-35mm, and they happily went ahead and developed the product as a Breakout Garden board. I described this in a blog post at: robots.org.nz/2021/07/09/the-paa5100je-near-optical-flow-sensor/ Now, there's still that range between the two sensors, i.e., between 35mm and 80mm, that's not covered by either, and while it's possible to mount a PAA5100J below a tall robot, one would be sacrificing ground clearance. As with many things in robotics, a compromise...

Thanks! If you mean the RGB LED, no. The code for the PMW3901 sensor doesn't send any data at all when it doesn't sense movement (so there's no default data rate), and then spits out x,y coordinate data as it does. I'm just listening for this data in a loop and updating the RGB LED as that data comes in.

The robot has a raspberry pi onboard so I would assume it uses that.

No, and there must be a good reason for that as I've viewed the tiny black and white movie that gets created so I get your point, but there must be some good technical reason why these sensors don't return a rotation delta. Even the significantly more expensive ones don't. Must be problematic to interpret image rotation in real time.

You could have two of them and extrapolate the rotation based on the x/y change delta between them.

@@ai-matt That's a really good idea -- I like that!

I've done some fairly extensive testing on the PixArt PAA5100JE, a sister to this sensor designed for close distances more suited to ground-based robots. I'd suggested to Pimoroni that it would be better than the PWM3901 (which is really designed for flying drones) and they're now selling it, which is great. What I've found is that you can calibrate to fairly accurate distance tracking on a single floor type, but if your robot goes from say grass to concrete to wood floor, the numbers sent back by the sensor will vary depending on surface, basicaly on surface complexity. It does still work on a "plain" floor if it has some kind of surface irregularity. On a smooth featureless tile its camera isn't able to discern detail, but you can help it out by adding additional white LEDs underneath to supplement the ones it has. But in short, it works better on surfaces that have *some* texture.

@@NewZealandPersonalRobotics I already bought PAA5100JE, which is only for close distance .now I've the PWM3901. .i'm going to tracking the ceiling. I've not installed on the robot yet Thank you very much for the reply.