Input Devices
This weeks task was to measure something: add a sensor to a microcontroller board that you have designed and read it.
Time of Flight Sensor
Device Choice
I wanted to use a time of flight sensor since it is very "visible" for me, and I have experience with the more advanced versions of it. Specifically, I have used the multizone vl53l7cx in the past, and have been on the emailing list for the vl53l9ca, and used the old vl53l1x as that is what my lab had at the time. Specifically, my lab had the Adafruit vl51l1x breakout board All of these different sensors are of the same series, being the STM time of flight sensor series, and they all do the same thing. They really accurately measure distance. There are virtually no drawbacks with them, they are small, highly accurate, low power consumption, and multi zone. Multi zone, is most simply explained by comparing it to a camera, the vl53l1x is a 1x1 zone, so it measures 1 distance, the vl53l7cx is 8x8 zone, so it measures 64 distances, think of them like pixels. The unreleased model, the vl53l9ca will be 42x52 zone, so it will be a fully fledged depth camera
Usage
Using a time of flight sensor, especially the vl53 series, is very easy. any sensor in the series, they usually have a polulu breakout board, for example the vl51l1x, which also means that polulu has created a library for that sensor. Those libraries can be found inside the library manager in all arduino IDEs 2.0 and onwards, and once installed includes example sketches
After downloading the library, it installs examples. For my purposes, I used the continuous example.
Wiring
As I spent most of this week working on output devices, I used a breakout board along with my [custom esp32-c3 board] that I designed before Fab academy. I did this because the board I designed last week as made for only one thing, and that was being the unrefined version of the logic of the stepper motor driver im designing for next week.
The pins I used for this were
3.3v: top left on my custom board, the specific breakout board I used uses level shifting, but the vl53l1x natively is for 3.3v devices GND bottom left of my custom board IO0 top right of my custom board, used as SCL IO1 top left of my custom board, used as SDA
Code Fixes
the example is not perfect, and needs to be modified, especially for a esp32-c3 chip. The esp32-c3 does not have set i2c pins, you have to define them as you enable i2c. You can do this by modifying this line
Wire.begin();
to
Wire.begin(SDAPIN, SCLPIN);
in my case, this was the 2 top left pins of the board, io0 for SCL and io1 for SDA, making the code
Wire.begin(1,0);
After uploading the code, I ran into a problem. This problem, which i've run into nearly every time I use that custom board, just requires me not to forget it. It was that I had not turned on USB CDC on boot, therefore disabling the built in serial converter while the board was running my code. This caused a lot of confusion, but after remembering it was an easy fix by changing it in tools -> USB CDC on boot Enabled
Processing
After reading the raw data, I wanted to go further. This is where a program called processing comes in handy. Through it, I can read data from the serial monitor and visualize it with graphs or 3d simulations. I have no experience with processing, but it is very identical to arduino code, even including the annoying fact that the sketch has to be stored in a folder and cannot have spaces in its name. It basically works like arduino in reverse, instead of making code for the microcontrller, the microcontrller will send data that the processing sketch processes in some way. This is done using the processing.serial.* library, which enables processing to read from the computers COM/DEVTTY ports. Processing is very easy to understand even if you know nothing, as it is essentially:
Define a object, E.G. box(100) makes a cube 100x100x100
Move that object, Translate(x,y,z).
Im not a good explainer, but I hope this gets the jist. You just say how to move something, using very basic commands, and it moves it.
Hero Shot
Now in motion picture!
Reflection
The Hardware
Im a fanboy of time of flight sensors. Just seeing how a sensor can (very accurately) measure distances up to 2 meters away just makes me want to make something with it. As I talked about above, I am on the mailing list for when the vl53l9ca comes out, and I will certainly find a project I want to make around the sensor. For some projects, you have something you want to make and you have to figure out how, and for others, you have something really cool that you want to make something with. If anybody else is interested in it, I found in a thread, that a STM employee said that the vl53l9ca would be released around the end of this year (2025). That sensor isn't just good for the high zone count, it also promises incredible ranges (up to 10 meters!) and highly improved accuracy in ambient light (one of the drawbacks of time of flight sensors)
The Software
The Arduino IDE is a jailcell for me. For some reason, on both my decent laptop and blazing fast computer, compiling a sketch for the esp32-c3 takes at least a minute. When I installed platformio on my computer (it does not work on my laptop), I found that it could compile in less than 10 seconds. I want to escape it, but the ease of use, and just the fact that my laptop cannot run most other IDE's due to it being windows on arm, has me chained up. As for the code specific to this project, it was really good, as polulu releases really good libraries for any boards that they make. Processing was also easy to work with, as its very easy to wrap my head around, and I would describe the code as very human readable. Also, one of my instructors, Dr. Taylor mentioned before how he used Processing alot previously for his final project, so looking at it helped me wrap my head around it.
Group Work
Design Files
The design files can be found here
While this week does not have a lot to it, I also included the design files for the PCB's I was making for output week, as a time capsule more for myself than any readers, and to show I wasn't just lounging around for most of the week (although this was during my schools spring break)