Lab 4 - Analog Inputs on UNO R3 - January 26, 2023

Covering the basics of using analog inputs with the Uno R3

Prep

I started this lab by familiarizing myself with some vocabulary. The Sparkfun website has a great tutorial outlining the difference between Serial and Parallel interfaces- the latter sends bits of data sequentially, one after the other, while the former uses an array of wires to transport. I found the following schematic very helpful in visualizing this process.

Visualization of Serial Communication

With a deeper understanding of the vocabulary, I read over the entire lab doccument again before getting to work on the first excercise.

I copied the code from the lab doccument, built it and uploaded it without any problems.

Screenshot of Excercise 1 code

Screenshot of Serial Monitor printing "hello!"

Taking the time to study each of the functions in the code, I took note of a new term/unit: Baud Rate: Unit of measurement for symbol rate, in this case, 9600 bits per second. I still have more questions about this, but for the sake of the lab, an intuitive understanding will do.

To assist with the process of rebuilding a voltage divider, I was able to refer back to my previous blog post for guidance, imagine that!
I opted to build the voltage divider using two 1k ohm resistors.

Photo of Voltage Divider breadboard layout

With the breadboard built out, I copied the code, taking the time to add my own notes in an effort to understand what it’s doing.

Screenshot of Voltage Divider Code

After building and uploading, I had what looked like success, although I couldn’t be sure until I converted the analog reading to volts.

Screenshot of Voltage Divider Serial Monitor

I copied the new “float” line of code and moved it around until I found the right place for it, which was after “reading” was initialized, but before the Serial Monitor is told to print “voltage”

Screenshot of modified code to convert to Volts

With the new conversion code installed, I uploaded it to the controller and had success.

Screenshot of Serial Monitor displaying accurately divided voltage (2.5)

Finally, I copied the print code to display both “reading” and “voltage” in the Serial Monitor

Screenshot of modified code to display "reading" and "voltage"

Screenshot of Serial Monitor displaying both "reading" and "voltage" values

From what I can gather, println is used to finalize a list of print requests. I think it means “print line”

Photo of voltage divider breadboard using a potentiometer

Uploading the same code as in Excersise 2.5, the Potentiometer Voltage Divider worked on first try. It was turned all the way down to start. I turned it all the way up, then gradually reduced it to zero as seen in the Serial Monitor

Screenshot of Serial Monitor displaying a decreasing range of voltage values

The lab doc suggested leaving the previous circut in place, but I decided to make some modifications for the sake of usability.

Photo of new breadboard layout w/ LED and potentiometer

I copied over the new bit of code, noting how the analogWrite function uses Pulse Width Modulation to simulate an analog signal to dim the LED

Screenshot of code to control brightness with potentiometer

I think that we divide reading by 4 to give the LED a signal output that wont overload it. We know from the first excercise that the signal from A0 provides values ranging from 0-1023, which would be too much for the LED.
Having created the code and built the breadboard, I tested it out. I had success, but the potentiometer that comes with the kit is terrible. I had to hold the base in place to get a consistent signal that didnt flicker.
With that said, my circut did work and I was able to adjust the brightness of the LED using PWM. At lower values, it was more obvious that I was using a modulated pulse to control the brightness.

Photo of successful LED control - low Brightness

Photo of successful LED control - high Brightness

I built the breadboard based on the schematic in the lab doc, and wrote the code, which was very similar to the first excercise.

Photo of breadboard including photoresistor and the passive buzzer

Looking at the Serial Monitor, I noticed that the ambient light in my room was producing a value around 375. When I cover it with my finger, I get it down to about 120. Shining a flashlight at it produces around 750.
Starting with my min/max values set at 120, 375, I uploaded the new code and got the buzzer working and repsonding to changes in light.
After a tinkering with the values, I found a min/max that worked with my room and created the widest diversity of tones on the buzzer.
I took a video as documentation of success but will omit that from the blog

At the end of this lab, I am left with a greater understanding of the basic capabilities of a microcontroller and am beginning to grasp how basic data (output voltage, ambient light) can be scaled up or down to control almost anything.
With that said, I still have some remaining questions about the differences between synchronous/asynchronous comunication.
Also, I am having a hard time grasping exactly which unit of measurement the controller is using when outputting the unconverted analog signal.
Moreover, I need some more elaboration on what baud rate controls and how to know when to alter the 9600 value
This lab took about 4.5 hours from beginning to end. I experimented with updating the blog directly as I completed the lab, which I think I will continue to do in the future.