It’s working! I have it sampling 10x per second and then I take zones 6,7, 10 and 11 (in the middle) and wire them up to the front 2 RGB LEDs so that they get dim when it senses something close. This will give me a visual indication of what the bot thinks that it sees ahead.

Now that I have my sensor talking to nerves, there are two follow-up items I need to address:

1. Update the tmf882x project to use circuit_gpio v2+
2. Mount the sensor in a reliable way to the trilobot

The first project can be all done in software and involves learning fun new things like how to do host-based testing of an I2C interface, but I’ve been programming all week for work. So I’m going to do the obviously wrong thing and start with project 2

The first thing I noticed is that the Trilobot “leans back a little”, so I put it on a flat surface and measured that the front of the trilobot is about 1cm higher than the back. And since I can’t be bothered to look up the trig I learned back in high school, I just drew a quick sketch in onshape and asked it to measure the angle for me.

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Then I grabbed the cad model I had previously made of the Trilobot and copied out the “front board” part, removed the holes for the ultrasonic sensor, and added a tilted face with this same angle.

Screenshot 2023-09-23 at 15.13.31958×1276 23.1 KB

Then I sketched in the mounting holes based on the TMF8821 datasheet that shows the location of the 3 mounting holes, and cut out those holes from the model.

Screenshot 2023-09-23 at 15.14.571100×1256 29.9 KB

Exported this to 3mf, sliced it and sent it to my 3d printer. We’ll see in 30min if it fits

Sparkfun has some helpful resources for this sensor:

• Quick hookup guide
• Datasheet

The key things to know about this sensor are that it uses a low power laser to sense distance of objects in front of the sensor. It uses some clever techniques to actually measure a grid of distances. There are some tradeoffs between how many measurements there are in the grid and how big the field of view is. I’m planning to use the built-in 3x3 configuration which samples distances 30x per second which should be able to detect both white and dark objects in bright sunlight at a distance of ~750mm.

Screenshot 2023-09-04 at 17.06.50542×578 27.6 KB