9. Input Devices

Group assignment:

Probe an input device's analog levels and digital signals.

1. Visualizing Signals for VL53L1X Distance sensor.

Our group has decided to work on VL53L1X Distance sensor with a Logic Analyzer.

About VL53L1X Distance Sensor, its specifications and Pinouts

This sensor is a Time-of-Flight ranging module with its range accuracy upto 4 meters and has fast ranging frequency upto 50 Hz.It is controlled through I2C interface with lower power consumption.The brand available was of Wavshare

Specifications

• Operating voltage: 3.3V/5V
• Dimension: 20mm × 24mm
• Mounting holes size: 2.0mm
• anging distance: 40 ~ 4000mm
• Ranging accuracy: ±5%
• Ranging time (min): 20ms (short distance mode), 33ms (medium/long distance mode)
• Field of view: 27°
• Laser wavelength: 940nm
• Operating temperature: -20 ~ 80°C

Pinouts of VL53L1X distance sensor:

• VCC: 3.3V/5V power input
• GND: ground
• SDA: I2C data pin
• SCL: I2C clock pin
• SHUT: shutdown control, connects to IO pin
• INT: interrupt output, connects to IO pin

Here is the link for VL53L1X Distance sensor

VL53L1X distance sensor with SALEAE Logic 8 Analyzer.

1.1 Adding library for VL53L1X distance sensor in Arduino IDE.

For the VL53L1X distance sensor we have referred its library from the Input devices class since the Arduino IDE does not containg library for this sensor.

We copied the link address and pasted under "preferences".

After adding the library package, searched for it under the library manager and installed it.

The libabry contains its examples so we haved choosed an example code to try the sensor.

This was the codes we used with this sensor.

#include <Wire.h>
#include <VL53L1X.h>

VL53L1X sensor;

void setup()
{
  while (!Serial) {}
  Serial.begin(115200);
  Wire.begin();
  Wire.setClock(400000); // use 400 kHz I2C

  sensor.setTimeout(500);
  if (!sensor.init())
  {
    Serial.println("Failed to detect and initialize sensor!");
    while (1);
  }

  // Use long distance mode and allow up to 50000 us (50 ms) for a measurement.
  // You can change these settings to adjust the performance of the sensor, but
  // the minimum timing budget is 20 ms for short distance mode and 33 ms for
  // medium and long distance modes. See the VL53L1X datasheet for more
  // information on range and timing limits.
  sensor.setDistanceMode(VL53L1X::Long);
  sensor.setMeasurementTimingBudget(50000);

  // Start continuous readings at a rate of one measurement every 50 ms (the
  // inter-measurement period). This period should be at least as long as the
  // timing budget.
  sensor.startContinuous(50);
}

void loop()
{
  sensor.read();

  Serial.print("range: ");
  Serial.print(sensor.ranging_data.range_mm);
  Serial.print("\tstatus: ");
  Serial.print(VL53L1X::rangeStatusToString(sensor.ranging_data.range_status));
  Serial.print("\tpeak signal: ");
  Serial.print(sensor.ranging_data.peak_signal_count_rate_MCPS);
  Serial.print("\tambient: ");
  Serial.print(sensor.ranging_data.ambient_count_rate_MCPS);

  Serial.println();
}

1.2 Connections of Sensor pins with a PCB board fabricated.

We have connected the SDA pin of sensor to the SDA pin of PCB board, followed by SCL to SCL, VCC to 5V of board, and GND to GND.We have used the fabricated PCB board of Dorji Gyeltshen.

We followed by compiling and uploading our program into Arduino IDE after selecting board and port and then clicked on "Serial Monitor" to try the working before we connected with our logic analyzer.

Our connection worked showing distances as we move the sensor.

Now, we went to connect with our sensor and program with the Logic analyzer.But we had to learn more about the Logic Analyzer for our actual work.

About Logic Analyzer

Logic Analyzer is an instrument that capture, display and measure multiple electronic signals simultaneously in a digital circuit.It helps to show the relationship and timing among many different signals in a digital system and are capable for analyzing digital communication protocols mainly I2C, SPI and Serial.

It is a best tool for debugging digital circuits and digital communication system.

We have used the saleae brand Logic 8 Analyzer.

About saleae logic analyzer

KEY SPECIFICATIONS of saleae Logic 8 analyzer:

• Eight Digital Channels
• 100 MSPS Digital Sampling (max)
• 25 MHz Max Digital Bandwidth
• Eight Analog Channels
• 10 MSPS Analog Sampling (max)
• 1 MHz Analog Bandwidth
• Recording Length Limited by Available RAM and Density of Recorded Data
• RGB LED, Customizable 24 bit Color

The Saleae Logic 8 USB Logic Analyzer is an 8 channel logic analyzer with each input dual purposed for analog data recording. The device connects to a PC over USB and uses the Saleae Logic Software to record and view digital and analog signals. It consists of 2x 4 Channel Wire Harnesses, 16 Micro-Gripper Hooks, Saleae Carrying Case, USB micro cable, and a Getting Started Guide.

Here is our reference link About saleae logic analyzer

1.3 Connections of VL53L1X sensor with Logic Analyzer.

We have installed the software of the logic analyzer from this link

We have used 3 pins of saleae logic 8 analyze and VL53L1X distance sensor with these connections:

• Pin 0 for SCL connected to SCL pin of PCB board with bread board.
• Pin 1 for SDA connected to SDA of PCB board with breadboard.
• Pin GND connected with GND of PCB board via bread board.

Note: The VCC of VL53L1X distance sensor is connected to 5V of PCB board for power supply.

1.4 Using Logic Analyzer's software to observe signals.

• Then, with the program running in Arduino IDE, we have connected the SDA and SCL lines to two channels of the logic analyzer.

2) Visualizing PMW signal on Oscilloscope

I explore about this sensor from this website.

A potentiometer is a variable resistor with three terminals whose voltage is adjustable manually with the help of a movable contact, in order to control the flow of electric current through it. Every variable resistor will have some kind of mechanical or electronic control to vary its resistance, based on the variation of this resistance the voltage across it and current through it is controlled with respect to Ohms Law. The most obvious use of the potentiometer which most of us have spotted is volume control in radios and other audio equipment.

A Potentiometer (or) POT is a passive electronic component that has two end terminals with a resistive element and the sliding contact called the wiper acts as the third terminal. The input voltage is applied across the two end terminals and the output is taken between the first end terminal and the sliding contact. The output voltage will be taken across any one of the two input terminals and the sliding contact. The POT helps us to use variable voltages in the same device.

This is the example code that we used to visualize the PWM signal mapped from the potentiometer sensor data. The PWM signal is also output to the led connected in the circuit.

/*
  Analog input, analog output, serial output

  Reads an analog input pin, maps the result to a range from 0 to 255 and uses
  the result to set the pulse width modulation (PWM) of an output pin.
  Also prints the results to the Serial Monitor.

  created 29 Dec. 2008
  modified 9 Apr 2012
  by Tom Igoe

  This example code is in the public domain.

  https://www.arduino.cc/en/Tutorial/BuiltInExamples/AnalogInOutSerial
*/

// These constants won't change. They're used to give names to the pins used:
const int analogInPin = A0;  // Analog input pin that the potentiometer is attached to
const int analogOutPin = 4;  // Analog output pin that the LED is attached to

int sensorValue = 0;  // value read from the pot
int outputValue = 0;  // value output to the PWM (analog out)

void setup() {
  // initialize serial communications at 9600 bps:
  Serial.begin(9600);
}

void loop() {
  // read the analog in value:
  sensorValue = analogRead(analogInPin);
  // map it to the range of the analog out:
  outputValue = map(sensorValue, 0, 1023, 0, 255);
  // change the analog out value:
  analogWrite(analogOutPin, outputValue);

  // print the results to the Serial Monitor:
  Serial.print("sensor = ");
  Serial.print(sensorValue);
  Serial.print("\t output = ");
  Serial.println(outputValue);

  // wait 2 milliseconds before the next loop for the analog-to-digital
  // converter to settle after the last reading:
  delay(2);
}

How does the above program work? This code reads an analog input from a potentiometer connected to pin A0 and uses it to control the brightness of an LED connected to a PWM-capable pin (analogOutPin = 4). The analogRead() function reads the potentiometer value (0 to 1023), which is then mapped to a range of 0 to 255 using the map() function. This mapped value is written to the LED using analogWrite(), adjusting its brightness. The sensor and output values are printed to the Serial Monitor, and a 2-millisecond delay ensures stable readings.

We connected the signal probe of oscilloscope at positive teminal of led and ground probe of oscilloscope to negative terminal of the led just so we can visualize the PWM signal coming to the leds which is again mapped from the potentiometer values.

Here is the visualization of varying PWM signal as we turn the knob of the potentiometer.