Input devices

Link to the group assignment How to create a plate

First of all

The xiao rp2040 can be either programed with arduino language or micropython, I decided to try both but starting with micropython.
To know how to get started with this microcontroller you con go straight to the Xiao rp2040 website There you will find everything you need about this micro controller and some other of the same brand.
xaio website
It looks like this, as you can see on the left side menu there are model of microcontrollers, and the rp2040 is on green, just bellow the selection there is a "Programming Language" button, click on it and it will display 3 options of languages, within those languages are arduino and micropython, I just clicked on micropython and the steps t follow will display on the center of the website. Just follow it.

Input means sensors, any kind of sensors, I made a ultrasonic distance sensor and and a joy stick.
It is important to say that this devices are sensors because they will tell the micro controller what's going on on the real world. This devices will also let us introduce data to our micro controller. NOTE, this devices will always be written on the code with "INPUT" on the pin declaration.

HC-SR04 Ultrasonic distance sensor

This sensor uses sound and time to measure distances, one of the cylinders (trigger) sends a sound wave, the sound wave travels until it collides with something on it's way, then, the sounds goes back to the second cylinder (echo) and the measurement takes into account the sound speed and the time it took to the sound to travel from the trigger, to the object and back to the echo. So you have to do some maths to get the result in cm, mm, in or ft. So here is the PINOUT:

Here is the most relevant information about the dataset:

Parameter	Value
Working voltage	DC 5V
Working current	15mA
Working frequency	40Hz
Max range	4m
Min range	2cm
Measuring angle	15º
Trigger input signal	10uS TTL pulse
Echo Output signal	Input TTL lever signal and the range in proportion
Dimension	452015mm

I took the information from this data sheet where you can also se more
Datasheet

Now, I consider important to say that I tried connecting the sensor to my xiao rp2040 and to a Arduino UNO, because this kind of sensors work better with arduino. As I'm using the xiao rp2040 with micropython I had to look for a way of making the sensor work with this program but I figured out it's almost the same as programming it with arduino But here I had an advantage, I looked on the one who teaches you anything YouTube for a way of dong it and I found Gold, a video and a library that made me everything easy. So...

Ultrasonic distance sensor with micropython

First I looked this video , it is a tutorial of how to use this sensor with micropython. This video took me to to this library , this is basically the same as in arduino but you just have to install it in your microcontroller and call it in your code.

How to install a library on your micro controller using Thonny

Open the .py file on Thonny like if you were going to writ a code, but just open it, don't modify it. One opened connect your microcontroller to the pc and make sure
conexion
this legend appears on the consol of Thonny, that means the microcontroller is connected to the interpreter. Now click on "saves as" immediately the interpreter will ask you ¿Where do you want to save the file? in your computer on in the rp2040 device?. You have to click on the "rp2040 device" option.
where so save the library
Just a help image. A new window will appear once clicked on the device option. Here you will have to give a name to the library, be careful with the name you write because this will be the one you will need to call on your program, so in my case I just named it as it was. "HCSR04.py". Don't forget to add the .py extension. Then click on ok and that's it, you have your library on your microcontroller.
saving the library
Now, if you go to the upper menu of Thonny on view and activate the option "files" you will see the files on the micro controller.

Use the library

We have the library installed, we just have to connect the sensor to the plate like in the pinout image, remember the "trigger" and "echo" pin go to a digital pin. Connect the micro to the pc and make sure Thonny reads it. Then we can make our code.
from hcsr04 import HCSR04 import utime while True: sensor = HCSR04(trigger_pin=28, echo_pin=29, echo_timeout_us=1000000) distance = sensor.distance_cm() print("Distance:", distance, "cm") utime.sleep(1) Yep, that's all we would need using the library. Just so you know, the first value when calling the library is the pin of the trigger pin, the second one is the echo pin, and the last one is the time that echo will hear in microseconds. You can read the commentaries of the library for more information.

Note, I had to use a protoboard because the sensor has plugs, my plate has also plugs, and I don't have jack wires
Here is a demonstration of the code and the sensor works.

The files

HCSR04 library (not mine)
Code to run the library

Checking the real measurements

The distance on the previous videos seems to be real, but how real is it, so I just measured it with a ruler. See it a judge your self. Just look how the end of the cylinders are on 30 cm and the code displays 29.00034 cm

Now with arduino

Arduino is almost the same thing, there is a tutorial on the Xiao rp2040 website that you can follow to run and program your rp 2040 with arduino.
The connections are the same on the arduino but the thing that do changes with arduino is the code, here we have to make from cero
IMPORTANT NOTE, arduino is a little pickier than Thonny so, once everything is installed, you have to disconnect and connect again the micro controller to he pc, and while you are connecting it you have to keep pushed the "B" button of the xaio rp2040 a new disk will appear as if you connected a USB, then you can send the code to the micro controller and it will run, now on you can just connect the micro controller, select it on the arduino ide and run the programs.

Let's see the code


    int trigger_pin = 6; 

    int echo_pin = 7; 

    float distance; 

  
  void setup() 

  { 

    Serial.begin(9600); 

    pinMode(trigger_pin, OUTPUT); 

    pinMode(echo_pin,INPUT); 

  } 

  
  void loop() 

  { 

    digitalWrite(trigger_pin, HIGH); 

    delayMicroseconds(10); 

    digitalWrite(trigger_pin, LOW); 

    double time = pulseIn(echo_pin, HIGH); 

    distance = (0.034 * time) /2; 

  
    Serial.println("Distance= "); 

    Serial.println(distance); 

    Serial.print("cm"); 

    delay(100); 

  }

Let me explain it, the working procedure of this sensor (in a few words) is, send a sound wave, wait for 1o microseconds and turn it off then, take the time detected on the echo receptor and do the following maths: time * by the speed of the sound on cm/s (0.034) and then divide it by 2 because you have to contemplate the distance form the trigger and the back to the echo. So the formula is this one: (time * 0.034)/2 this is the distance in cm

The file

Arduino file

The Joystick

This joystick is the second sensor I used, it is basically 2 perpendicular but joined potentiometers, one for the movement on x axis and one for the movement on y axis, it also has a push button on pull up resistor. So this module has 5 pins

Vcc
Input voltage
GND
Output GND
VRX
Output x axis
VRY
Output y axis
PW
Output pushbutton

IMPORTANT NOTE, as this joystick works with potentiometers, it's outputs will be analogic except for the push button, this will be digital. Now the specifications

Parameter	Value
Operating voltage	5 V
Potentiometer resistor value	10k
x and y axis output	Analogic
Push button output	Digital
Dimentions	34x26x32 mm

This information was recovered from the following Datasheet

To use this module we also have to know how does this work, you see it as a cartesian plane, where your limits are 0 and 1023 (1023 is because we are converting voltages into binary values). Each potentiometer has it's 0 and it's 1023 so you will be working with coordinates. Let's take a look to the image of the datasheet:

Yep, here yu can say the micro controller where the joystick is going. A quick example would be: if x axis and y axis are close to 512 or 512 don't do anything, but if x axis is 512 and y axis is 1023 go forward. And so on. Once again the push button is on PULL_UP resistor and I think that's the basic to configure it

Th wiring

Just like on the datasheet but on a protoboard

Now let's program it with micropython

The code


      import machine 

      import utime 


      xaxis = machine.ADC(3) 

      yaxis = machine.ADC(2) 

      push = machine.Pin(0, machine.Pin.IN, machine.Pin.PULL_UP) 


      while True: 

        x = xaxis.read_u16() 

        y = yaxis.read_u16() 

        print("x: ", x) 

        print("y: ", y) 

        print(push.value()) 

        utime.sleep(.5)

As simple as this, this code just reads the values of the potentiometers an the push button and print them on the console. Is important to mention that here in micropython, as the code just read in 16 bits the range for the potentiometers will be 0 - 65535.
And we are using a new function of machine "ADC" Analogic Digital Converter, so with this function you can write the number of the analogic pin on the micro controller instead of the general pin or the digital pin, also this will convert the microVolts values to a binary value with help of the .readu_16() command.

The file

Joystick file

The evidence

The same joystick with arduino

Infrared motion sensor (PIR/HC-SR501)

This sensor is what the name says, it detects movement, but specially the living creatures movement, because it works with infrared signals. It is important no mention that this module has different modes of operation, and you can change the time and the range of response with the 2 potentiometer it has. It has only one output digital pin aaaaaaaand that's the quick "you need to know"
Remember the pinout, because on the plate there says nothing (excuse the spanish on the image but it is the perfect image ):

Let's go with the specifications

Parameter	Value
Operating voltage	5 V
Consume current	less than a milliampere
Detection distance range	3-7 m
Delay time of response	3 sec - 5 min
Detection angle	110º
Settings	Detection range potentiometer and response time potentiometer
Type of trigger output	Single shot and rettrigerable
Volt range output	0-3.3 V
Initialization time	1 min
Working temperature	15º-70º
Dimentions	3.2x2.4x1.8 cm

You can see more on this manual Alright, there are many ways to use this sensor, I'll go with the basic one, just connect the 3 main pins, set the lowest range (3m) and the fastest response (3) that's it, let's see the wiring and the potentiometer positions

The code


      import machine 

      import utime 


      xaxis = machine.ADC(3) 

      yaxis = machine.ADC(2) 

      push = machine.Pin(0, machine.Pin.IN, machine.Pin.PULL_UP) 


      while True: 

        x = xaxis.read_u16() 

        y = yaxis.read_u16() 

        print("x: ", x) 

        print("y: ", y) 

        print(push.value()) 

        utime.sleep(.5)

The file

Here is the file

The evidence

Learning outcome

Always check the datasheets of the sensors you are using they will tell you how to use them, connect them, how much voltage they consume, how many current they need, the kind of output. Basically everything about the sensor or the input device.