Week 8

Use an EDA tool to design a development board to interact and communicate with an embedded microcontroller

Kicad

The software I used to design my boards is Kicad

KiCad is a free, open-source software suite for electronic design automation (EDA). It provides tools for schematic capture, PCB layout, 3D viewing, and SPICE simulation, making it suitable for designing complex electronic circuits and printed circuit boards. It includes a rich library of components and allows for custom symbol creation. The software is versatile enough for both beginners and advanced users.

For more information, you can visit their official website.

Firstly, I would like to thank my instructor for teaching us the basics of PCB designing patiently.

But other than my instructor, I referred to a youtube playlist by embed ideaEmbed Idea's videos on PCB desiging is detailed and informative. It is a perfect resource for beginners like me.

Designing

After getting a good basics lesson on PCB designing in Kicad by my instructor and youtube videos, I started my design.

I started my schematic with this as a reference, I created the sketch for my final project board. And also considering the basic circuit for the ATtiny44 I found in embedded programming page under the fab academy site.

Starting a Project

Firstly you nedd to add the symbol libraries.

To get familiar with using the software. It is a must you know the workspace well

Starting the schematic

Adding symbols

Adding power symbols

After adding symbols and making connections

Adding footprints

Footprints in KiCad are like outlines or stamps that show where to place electronic components on a printed circuit board (PCB). They define the size, shape, and layout of pads and solder mask openings for soldering components onto the board.

Go to "Tools" and click on "Assign footprints"

At first I connected every symbol with wires and added a resistor for every switch I had.

Then I remembered that our instructor taught us about labels!

Then after finishing the design for the schematic

Use the following tools

Electronic Rule Checker(ERC)

It's a feature that automatically checks your schematic for common electrical errors or rule violations. When you run the ERC, KiCad analyzes your schematic to ensure that it adheres to certain electrical design rules and standards. ERC in KiCad acts like a spell checker for your schematic, helping you catch potential mistakes or problems that could cause issues in your circuit. It checks things like unconnected pins, duplicate net names, incorrect power connections, and other common errors to ensure your design is electrically sound. Running ERC before moving to PCB layout helps prevent costly mistakes and ensures a smoother design process.

Annotate

Annotation in KiCad refers to the process of assigning unique identifiers or reference designators to the components in your schematic. These identifiers help distinguish one component from another and are essential for the proper organization and assembly of your circuit.annotation in KiCad ensures that each component in your schematic has a distinct name or number so that they can be easily identified during the design process and when assembling the physical circuit board. This helps avoid confusion and ensures that all components are correctly placed and connected.

Go to "Tools" on the top tool panel, and click on "Annotate Schematic"

Design Rules and Constraints in PCB Design

1. Minimum Distance Between Trace Lines

Determined by the endmill diameter used in manufacturing. Smaller endmills allow tighter spacing. Correct spacing avoids short circuits and ensures signal integrity.

2. Minimum Gap Between Pads

Set based on endmill size. Ensures clearance to avoid solder bridging during assembly.

3. Design for Manufacturability (DFM) Rules

• Component Spacing: Prevents complications during assembly.
• Trace Width and Spacing: Avoids electrical shorts and maintains signal integrity.
• Solder Mask Webbing: Specifies minimum solder mask width to prevent bridging.
• Solder Paste Coverage: Ensures reliable solder joints.
• Silkscreen Coverage: Prevents overlap with pads or vias.

4. Electrical Constraints

• Measured Trace Lengths: Critical for timing-sensitive signals.
• Matching Trace Lengths: Ensures equal lengths for differential pairs.
• Trace Routing Topologies: Minimizes noise and crosstalk.
• Differential Pair Trace Routing: Maintains signal integrity.
• Controlled Impedance Routing: Specifies trace widths and spacing.

5. 3D Design Rules and Constraints

• Component Clearance: Ensures space around components.
• Object Collision Reporting: Detects component or edge collisions.

6. Setting Up Rules in CAD Systems

Tools like Cadence Allegro PCB Editor manage rules effectively.

• Trace Routing Rules: Set specific widths and spacing.
• Component Spacing Rules: Ensure adequate clearance.
• Via Assignments: Define via usage for specific nets.

Summary

Defining these rules early ensures successful PCB layout and manufacturing. Tailor rules to specific manufacturing capabilities and electrical requirements. Continual refinement from the schematic phase through layout ensures all design aspects are covered.

Here is my settings

Switching to PCB Editor

Image Source

Like you ran ERC for schematic, it is also important for us to run the design rules checker for PCB design to ensure there is no design error in your board and guide you to improvise your board.

Additing predefined netclass

While creating routes, we should also keep in mind to avoid right angle connections because according to Altium, "high-frequency signals emit Radio Frequency radiation at every 90 degree turn of the copper track." (Altium, 2018, para.3)

Sir Rico suggested us to keep the width of the signal pin routes 0.4 mm and power pin routes 0.8 mm so that the power can flow smoothly and to help us differentiate the signal and power routes.

Adding predefined net classes in the PCB editor in KiCad allows you to organize and manage groups of nets with similar properties, such as signals or power connections. This feature simplifies the routing process by applying specific design rules or settings to entire groups of nets at once.

While editing the pcb, I needed more 0 ohm resistors.

These are the versions of my board(I am a beginner in making connections in PCB editor and will get better each time)

Then finally I was relieved but..

.....I ended up with 19 0ohm RESISTORS!!!/p>

Exporting the design

Generating RML file

To generate the .rml file I used Mod CE

Mods CE (Computational Environment) is an open-source, browser-based platform designed for creating, editing, and running computational workflows. It is commonly used for digital fabrication, allowing users to connect various modules to process and generate machine code for different types of manufacturing machines.

Printing

I will be using the Roland SRM 20

VPanel for SRM-20

Image Source

• Current Coordinates of Tool: Shows the X, Y, and Z positions of the tool.
• Buttons to Move Spindle:
  • X-Y Plane: Moves the tool left, right, forward, and backward.
  • Z-Axis: Moves the tool up and down.
• Set Origin Point:
  • X/Y and Z: Sets the starting point for milling in the X-Y plane and Z-axis.
• Cursor Step: Selects the distance the tool moves per step.
• Move to Origin: Returns the tool to the origin point.
• Speed and Spindle: Controls the movement speed and spindle rotation.
• Buttons:
  • Cut: Starts the milling process.
  • Pause: Pauses the operation.
  • Cancel: Stops the operation.

UH OH...

I set the origins wrong and not 0 while making the .rml file. And it resulted in the printer milling the wrong way and breaking a 1/64 drilling bit.

But our instructor gave us a new drilling bit! YIPPEY!!

Becuase I broke a drilling bit, Damzang helped me set the machine up and create the .rml file.

Printing(milled the right direction)

Routes

Edge cuts

Taking out!

Done!!

Soldering

Components

Programming

With the help of Yangtshel(My friend), I tried programming my board using AVR ISP. But the code never uploaded. And everytime we connected the GND of my board to the GND of the Arduino UNO it kept losing connection. I showed it to my Instructor and he helped me fix the problem. It turned out that the problem was with my 19 0ohm RESISTORS! So the main problem was caused when I added a 0 ohm resistor of which one side connected to VCC and the other to GND. And the reason why you can't connect a resistor between a VCC and GND is because(As explained by my friend Yangtshel to me) connecting VCC and GND directly with a 0 ohm resistor effectively creates a short circuit between the power supply's positive and ground terminals. This short circuit could potentially damage the power supply or other components in the circuit(The GND and VCC always have to be seperated)

That is why the below didn't work. I didn't remove the 0 ohm resistors that created a short circuit in my board.

After my instructor pointed the problems out and left me to identify what the problem really was, I concluded that:

Programming

I programmed my board using Arduino Uno as my programmer!

To use Arduino as my programmer I referred to the following image for the connections

Image Source

Firstly making the Arduino Uno a programmer

Open Arduino IDE

• Go to "File"
• Then to "Examples"
• Choose the option "ArduinoISP"
• then finally under "ArduinoISP" choose "ArduinoISP"

Then choose the correct COM PORT to upload your code to your board, Then upload

Uploading the blink code to my board using the Arduino Uno as the programmer

After making the the Arduino UNO a programmer

• Go to File
• Then "Examples"
• Then "Basics"
• Select "BLINK"

Then make the following changes according to your board

• Go to "Tools"
• Under that click on "Boards" and choose your board, for me I chose "ATTINYCORE", since I am using ATTINY44
• Then choose your board

• Go to "Tools"
• The "PORT"
• Make sure you ahve the chosen the right COM PORT

After that again

• Go to "Tools"
• Then "Chip", since when I chose my board there were two options: ATTINY44 AND ATTINY84. Then I chose ATTINY44
• Then click on "Clock Source(only set on bootload): "20 MHz(external)", and I chose "20MHz(external)" since my attiny44 functions on an internal 8MHz but I added an external 20MHz oscillator for which I had to select that.

Then

• Change the "LED_BUILTIN" to the pin you connected your LED.

Then finally

• Go to "Sketch"
• Then "Upload using Programmer"

Arduino Example Blink Code

  /*
    Blink
  
    Turns an LED on for one second, then off for one second, repeatedly.
  
    Most Arduinos have an on-board LED you can control. On the UNO, MEGA and ZERO
    it is attached to digital pin 13, on MKR1000 on pin 6. LED_BUILTIN is set to
    the correct LED pin independent of which board is used.
    If you want to know what pin the on-board LED is connected to on your Arduino
    model, check the Technical Specs of your board at:
    https://www.arduino.cc/en/Main/Products
  
    modified 8 May 2014
    by Scott Fitzgerald
    modified 2 Sep 2016
    by Arturo Guadalupi
    modified 8 Sep 2016
    by Colby Newman
  
    This example code is in the public domain.
  
    https://www.arduino.cc/en/Tutorial/BuiltInExamples/Blink
  */
  
  // the setup function runs once when you press reset or power the board
  void setup() {
    // initialize digital pin LED_BUILTIN as an output.
    pinMode(8, OUTPUT);
  }
  
  // the loop function runs over and over again forever
  void loop() {
    digitalWrite(8, HIGH);  // turn the LED on (HIGH is the voltage level)
    delay(1000);            // wait for a second
    digitalWrite(8, LOW);   // turn the LED off by making the voltage LOW
    delay(1000);            // wait for a second
  }
      

Explanation

This code is a basic example of how to blink an LED using an Arduino. Here's a step-by-step explanation:

Header Comments

The comments at the top of the code provide information about the purpose of the code and its modifications over time. It also mentions the pins to which the on-board LED is connected for different Arduino models.

Setup Function

  void setup() {
    // initialize digital pin LED_BUILTIN as an output.
    pinMode(8, OUTPUT);
  }
      

The setup() function runs once when the Arduino is powered on or reset. It initializes pin 8 as an output. This is necessary because the pinMode function configures the specified pin to behave either as an input or an output.

Loop Function

  void loop() {
    digitalWrite(8, HIGH);  // turn the LED on (HIGH is the voltage level)
    delay(1000);            // wait for a second
    digitalWrite(8, LOW);   // turn the LED off by making the voltage LOW
    delay(1000);            // wait for a second
  }
      

The loop() function runs repeatedly in a loop. Here's what it does:

• digitalWrite(8, HIGH); - Sets the voltage of pin 8 to HIGH, which turns the LED on.
• delay(1000); - Pauses the program for 1000 milliseconds (1 second).
• digitalWrite(8, LOW); - Sets the voltage of pin 8 to LOW, which turns the LED off.
• delay(1000); - Pauses the program for another 1000 milliseconds (1 second).

This cycle repeats indefinitely, causing the LED to blink on and off with a one-second interval.

Testing

To make sure, (My friend Yangtshel's advice) Initialize the wrong digital pin LED_BUILTIN to check whether your board is really programmed or not.

Communication with my Final Project board

I have tried communication with my Final project board, please visit the link below for the files and the process for the board I used

• Final Project Development

I refered to Zin Tech Ideas since it is my firat time using the NTC thermistor module

I connected a NTC thermistor module to my Final Project board with connections on a breadboard.

Connects I made will be:

• VCC->3.3V
• GND->GND
• AO->PA4

Programming

This is the code I used, the sources I refer to would be Zin Tech Ideas and is modified for my requirements by chatgpt

  #include 


    #define SENSORPIN A5  // Analog pin connected to the analog output of the LM393 module
    #define THRESHOLD_TEMPERATURE 35 // Temperature threshold in Celsius
    
    
    void setup() {
      Serial.begin(115200);
      pinMode(SENSORPIN, INPUT);
    }
    
    
    float readTemperature() {
      int analogValue = analogRead(SENSORPIN);
      float voltage = analogValue * (5.0 / 1023.0);
    
    
      // Assuming a 10k NTC thermistor with a 10k resistor in a voltage divider configuration.
      float resistance = (10000.0 * voltage) / (5.0 - voltage);
    
    
      // Convert the resistance to temperature using the Steinhart-Hart equation
      float temperature = 1.0 / (0.001129148 + (0.000234125 * log(resistance)) + (0.0000000876741 * log(resistance) * log(resistance) * log(resistance)));
      temperature = temperature - 273.15; // Convert Kelvin to Celsius
    
    
      return temperature;
    }
    
    
    void loop() {
      float temperature = readTemperature();
      Serial.print("Temperature: ");
      Serial.print(temperature);
      Serial.println(" °C");
    
    
      if (temperature > THRESHOLD_TEMPERATURE) {
        Serial.println("Threshold exceeded, powering DFPlayer...");
      }
    
    
      delay(1000); // Wait for 1 second before reading again
    }
    

But it was not compatible with my XiaoESP32C3

I asked chatgpt to modify it for me to make it compatible for XiaoESP32C3

  
    #include 


      #define SENSORPIN A0                // Analog pin connected to the analog output of the LM393 module
      #define THRESHOLD_TEMPERATURE 35    // Temperature threshold in Celsius
      
      
      void setup() {
        Serial.begin(115200);
        pinMode(SENSORPIN, INPUT);
      }
      
      
      float readTemperature() {
        int analogValue = analogRead(SENSORPIN);
        float voltage = analogValue * (3.3 / 4095.0);  // Adjust for ESP32C3's ADC range
       
        // Assuming a 10k NTC thermistor with a 10k resistor in a voltage divider configuration.
        float resistance = (10000.0 * voltage) / (3.3 - voltage);  // Adjust for ESP32C3's maximum voltage
       
        // Convert the resistance to temperature using the Steinhart-Hart equation
        float temperature = 1.0 / (0.001129148 + (0.000234125 * log(resistance)) + (0.0000000876741 * log(resistance) * log(resistance) * log(resistance)));
        temperature = temperature - 273.15; // Convert Kelvin to Celsius
      
      
        return temperature;
      }
      
      
      void loop() {
        float temperature = readTemperature();
        Serial.print("Temperature: ");
        Serial.print(temperature);
        Serial.println(" °C");
      
      
        if (temperature > THRESHOLD_TEMPERATURE) {
          Serial.println("Threshold exceeded, powering DFPlayer...");
        }
      
      
        delay(1000); // Wait for 1 second before reading again
      }
      
  

Files

Board