Group Assignment on Input devices

🖨️ Week 9 - Input Devices (Group Work)

In this week's group assignment, our task was to probe the analog and digital signals of various input devices. Aleksi had built several sensor test modules, from which we measured both digital and analog signals.

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🟢 Sensor Testing

A small VL53L1X Time-of-Flight (ToF) laser-ranging sensor was tested by repeatedly placing a piece of cardboard in front of the sensor and then removing it. The software displayed the measured distance at a rate of approximately 4 Hz. According to the datasheet, a ranging frequency of up to 50 Hz is possible, although this likely depends on the sensor's operating mode. For example, the sensor features a programmable Region of Interest (ROI) on the receiving array, allowing the field of view to be narrowed. It also supports short- and long-distance modes, which can affect performance. A more thorough evaluation would be necessary if this component were to be used in a final product.

In the image below, a section of the measured I²C communication between the microcontroller and the VL53L1X is shown. The yellow signal is the SCL (clock) line, and the blue signal is the SDA (data) line. This includes standard I²C features such as Start and Stop conditions, Read/Write bits, ACK/NACK responses, the slave address, and data frames. Most parts of the communication remain consistent across each cycle, except for the distance measurement data, which appears in the middle section of the digital signal.

Here is a video of the Time-of-Flight (ToF) laser-ranging sensor measurement setup, where a target is repeatedly placed in front of the sensor.

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A potentiometer test was also conducted. A potentiometer is a variable resistor, functioning here as a voltage divider. The analog voltage output changes as the knob is turned, allowing the microcontroller to detect rotational motion. The analog output signal from the potentiometer is shown in the blue waveform below:

Below is a video of the potentiometer measurement:

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In addition to these, a thermistor and a photodiode were tested. They worked similarly but responded to temperature and light intensity, respectively.

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🎯 Summary

• The I²C protocol enables multiple sensors to communicate over the same two data lines (SDA/SCL).
• There is a sensor available for measuring nearly every type of physical phenomenon.