My CircuitPython assignments!
New year, new programming language, new IDE, and new hardware. This assignment was an introduction to the CircuitPython programming langauge, the Mu IDE, and the Metro M0 Express. The Metro looks like an Arduino, but it is very different. It runs CircuitPython. And it also has a neopixel RGB LED built in. This assignment was to code our new Metro to have an LED fade in and out.
I'm still trying to figure out if I like the Fritzing breadboard or the Fritzing schematic better, so here's both.
I completed this project by making a PWM object and varying the duty cycle. PWM means Pulse Width Modulation. A PWM signal is a square wave. By varying the duty cycle (how often the pulse was up or down), I was able to vary the apparent brightness of the LED. I made the PWM object like this: led = pulseio.PWMOut(board.D3, duty_cycle=0, frequency=5000) and then I changed the duty_cycle property.
From this page, I learned that the Metro M0 Express has PWM on the following pins: A2, A3, A4, D0, RX, D1, TX, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, SDA, SCL, NEOPIXEL, SCK, MOSI, MISO.
There is NO PWM on: A0, A1, A5, FLASH_CS.
I also learned that the Metro M0 Express can do true analog, thanks to a DAC (digital to analog converter) on pin A0. You can use analogio to write a value between 0 and 65535 (216-1) and that will correspond to a voltage between 0 and 3.3 V. The DAC on the SAMD21 is a 10-bit output, from 0-3.3V, so that should get me a resolution of 0.0032 Volts. Nice. But, I didn't use that though. I used PWM.
The goal of this assignment was to use CircuitPython to make a servo move, using capacitive touch. Capacitive touch is cool because the Metro can detect when you're touching wires and you can use that as input.
Just like in the last assignment, I used a PWM object. In this case, the PWM object controlled the servo. Using the Adafruit motor library, I could just attach that PWM object to a servo and then send the servo angles like myServo.angle = 90. Piece of cake. The touch part was pretty easy, too. Just import the touchio library, make a touch object like touchLeft = touchio.TouchIn(board.D2) and then just get the value of that object, touchLeft.value.
Check out this clever function I wrote
def constrain(n, minn, maxn):
return min(max(n, minn), maxn)