Week 8

Electronic Design

Fab Academy 2024
Riichiro Yamamoto

Group Assignment

SAMD11

Components

KiCad

Inkscape

MODs

Milling

Program with Platform IO

Program as a programmer with Arduino

Blink the SAMD11

Touch the SAMD11

Dear My Friend

This week I was introduced to Electronic Design, which is selecting components and designing your own PCB. The main goal for this week was to design, fabricate, and program the development board. The development board is a board you use to control other boards.

The basic workflow goes like this

Decide what you want the development board to do
Select microcontroller understand Pinpout
Find out what components you need
Design the board with Electronic Design Automation (EDA) software(for me KiCad)
Adjust SVG file in CAD software (for me Inkscape)
Use MODs to generate files for Milling machine
Milling PCB
Program the board

Hope you enjoy

Riichiro Yamamoto

Group Assignment

this week's group assignment was to use the test equipment in your lab to observe the operation of a microcontroller circuit board. Send a PCB out to a board house.

Here is the link to the group assignment page

SAMD11

For my PCB, I decided to use SAMD11C14A (SAMD11) because it has many pins and has the PTC peripheral capable of step response touch sensing without any additional hardware. As a reference, I used SVG PCB splines by Quentin Bolsee

Components

By looking at the reference, another reference, DataSheet, and SAMDino by Adrian Torres, I started to understand how my board should work.

Also, by asking a bunch of questions to my tutors, I finally figured out what components I needed on my board. Below is the list of components.

Microcontroller SAMD11
USB Connection (for programming directly from PC)
Voltage Regulator (for converting 5V to 3.3V)
2 Capacitor (for voltage regulator)
SWD Vertical Male Pin (for programming though RP2040)
5 Horizontal Male Pin(for connecting additional board)
LED (for checking )
Registor (for LED)

KiCad

I was recommended to use KiCad for making schematics and tracing for PCB, because our lab environment aligns with it. Below is the workflow of KiCad.

Install & Set UpLibrary

Install KiCad
Open Kicad
Download as Kicad Fab Library from this page this page as a Zip file
It is important to know the location of the Zip file because KiCad will reference it
Preference, Manage Symbol Libraries
Only for the first time, Choose Copy Full Global Symbol Libraries
it will load all the default libraries
Select all the libraries, and press the space key to deactivate, (good to do this because it takes time to load every time if they are active)
Activate only the library you want to use( also it makes easier to find components)
There are Global Library and Project Specific Library, for now, Global Library is good. If you have a library only for specific projects then have it in Project Specific Library
Add Library, go to the Zip file, and look for a file named fab.kicad_sym
Make sure the Fab library is active and close the window
Preference, Manage Footprint Libraries
Only for the first time, Choose Copy Full Global Footprint Libraries
it will load all the default libraries
Select all the libraries, and press the space key to deactivate
Add Library, go to the Zip file, and look for a folder named fab.pretty
Make sure the Fab library is active and close the window
Now KiCad has Symbol Library and Footprint Library ready to be used

Schematic

Go to Schematic Editor
Add components by Add Symbols (A)
Add label by Add global labels (Ctrl+L)
Connect components and labels by Add a wire (W)
Adjust placements to understand easier
Move on to PCB Footprint by Open PCB in board editor button

PCB Footprint

Update PCB with change made toschematic
Place all the footprint
Adjust placement by Move (M), Rotate (R), Grab (G) and Flip (F)
See blue line for connection
File - Board Setup - Net Classes
Change default parameters
Clearance 0.4mm, Track Width 0.3mm, Via Size 1.2mm, Via Hole 0.8mm, uVia Size 0.3mm, uVia Hole 0.1mm, DP Width 0.3mm, DP Gap 0.4mm
Draw trace by Route track (X)
Change labels and orders in schematic if necessary
Update PCB every time change made to schematic
Check for errors and warnings by Design Rules checker window
dont have to worry about warnings
Fix errors unless it is expected
Export as SVG file

If there are components that are related to the outline(like USB, and Horizontal Pinns), it is good to have lines for it before exporting, so that they can be used as a guide when drawing an outline in Inkscape.

Inkscape

Open SVG file in Inkscape
Defferenciate trace & footprint, holes, and outline
Make layer for trace, holes, outline
Move to layers according to what it is
Make Background layer, create black background (Change opacity to see easier)
Change stroke to white, fill to none for trace
Change stroke to none, fill to white for footprint
Change stroke to black, fill to white for outline
Change stroke to white, fill to black for holes
Draw an outline with 0.8mm thickness
Exporting should be PNG with DPI 1000
Export with outline size by Selection. Always export in the same size
Export outline with background
Export trace with background
Export holes with background
Move on to MODs

MODs

I used MODs to prepare files for milling. I did this with the same workflow from Week 4 Electronic Production

Problem

A problem I had during this phase was that my milling preview was showing unnecessary cuts for the outline. It was caused by the outline PNG not having a transparent background so MODs were acting weird. Simply I added a black background to fix this issue.

Milling

Again. I did this with the same workflow from Week 4 Electronic Production

A small Trick I learned

My first trial for milling trace was not milling through the copper layer, and I could see shiny traces. I asked for help to my tutor and he told me this trick. While the end mill is milling when the Z axis is -0.10mm, cancel the job, and the end mill will stop in the place. Use the current Z-axis value (-0.10mm) to reset the Z origin, so the next job will be milled 0.10mm deeper. Don't forget to move the end mill up after setting the origin and before you move anything.

Program with Platform IO

Problem

After milling and soldering, it was time for programming. I was going to use PlatformIO since I had a super long compiling sketch time problem with Arduino. However, I could not find a SAMD11 to select as a board. There was only SAMD21. After quick research on this issue, I found out that the board support for SAMD11 was previously requested by users and it has not been updated yet.

After I discussed this problem with my tutor, he advised me to try Arduino once again.

Program as a programmer with Arduino

To flash SAMD11 and make it a programmer, I needed to use another board to flash SAMD11. In this case, I used Quentorres PCB with XIAO RP2040 which I made during Week 4 Electronic Production.

To use Quentorres as a SWD programmer to flash SAMD11, I simply followed the How to Use as a Programmer guide made by Adrian Torres.

The workflow is below.

Download the uf2 file from here
Connect Quentorres to PC
Boot & Reset Quentorres
PC will read Quentorres as USB and open its folder
Place the uf2 file inside the folder
Quentorress will reset automatically
Now it should be a functional SWD programmer

To flash SAMD11, I continued following the same page and used Flashing a SWD target guide made by Adrian Torres.

The workflow is below.

Solder 4 vertical pins on the blank trace of the Quentorres
Connect those 4 pins to 4 pins of SAMD11 PCB with 4 wires
4 pins are GND, DIO, CLK, and RST
Make sure they are connected with the same pin because orientation matters
Copy URL shown in FAb SAM core for Arduino
Open Ardurino
File - Preference - Additional board manager URLs
Paste the URL of FabSAM core
Select Generic D11C14A in board manager
Change programmer to CMSIS-DAP from Tool tab
Select USB port
Burn Bootloader from Tool Tab

Problem

I was not able to burn the bootloader for the first time. The error message was saying something like there was no response from the SAMD11 side, so I assumed the might be something wrong with my SAMD11 board. I checked the connection with the multimeter. They also scraped unnecessary copper around the USB port and added card paper underneath to fit nicely into the USB port. Still, it was showing me the error. Then my tutor checked my components carefully and found the component that I thought voltage regulator was not a voltage regulator. My tutor replaced it and I was able to burn the bootloader.

Blink the SAMD11

After bunning the bootloader, I was able to directory program SAMD11. First I did a Blink example as a quick test. Thankfully this time Ardurino did not take a long time to compile the sketch, so it means I can finally play with programming in Arduino.

/*
                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
              */
              
              const int ledpin = 15;
              
              // the setup function runs once when you press reset or power the board
              void setup() {
                // initialize digital pin LED_BUILTIN as an output.
                pinMode(ledpin, OUTPUT);
              }
              
              // the loop function runs over and over again forever
              void loop() {
                digitalWrite(ledpin, HIGH);  // turn the LED on (HIGH is the voltage level)
                delay(1000);                      // wait for a second
                digitalWrite(ledpin, LOW);   // turn the LED off by making the voltage LOW
                delay(1000);                      // wait for a second
              }

Touch the SAMD11

Next, I wanted to play with the TouchPad that I included on the board. I followed the SVG PCB spline by Quentin Bolsee and was able to blink LED by TouchPad.

The workflow is below.

Install the Adafruit Freetouch library from Adafuit_FreeTouch as Zip file
Sketch tab - Include Library - Add Zip Library
add the Freetouch Zip file
Use the minimal example from Adafuit_FreeTouch
Change TouchPad pin according to my boad
Add, Serial.begin(115200);
Add, Serial.printIn(qt_value);
Add, delay(500);
Upload the code

#include "Adafruit_FreeTouch.h"

                const int ledpin = 15;
                
                Adafruit_FreeTouch qt1(4, OVERSAMPLE_4, RESISTOR_50K, FREQ_MODE_NONE);
                Adafruit_FreeTouch qt2(2, OVERSAMPLE_4, RESISTOR_50K, FREQ_MODE_NONE);
                Adafruit_FreeTouch qt3(14, OVERSAMPLE_4, RESISTOR_50K, FREQ_MODE_NONE);
                
                void setup() {
                  qt1.begin();
                  qt2.begin();
                  qt3.begin();
                  Serial.begin(115200);
                  pinMode(ledpin,OUTPUT);
                }
                
                
                void loop() {
                
                  int qt1_value = qt1.measure(); // read 10-bit value
                  Serial.println(qt1_value);
                  delay(100);
                
                  if(qt1_value>500){
                    digitalWrite(ledpin, HIGH);
                  }
                   else{
                    digitalWrite(ledpin, LOW);
                  }
                  
                  int qt2_value = qt2.measure(); // read 10-bit value
                  Serial.println(qt2_value);
                  delay(100);
                
                  if(qt2_value>500){
                    digitalWrite(ledpin, HIGH);
                    delay(100);
                    digitalWrite(ledpin,LOW);
                    delay(100);
                  }
                
                  int qt3_value = qt3.measure(); // read 10-bit value
                  Serial.println(qt3_value);
                  delay(100);
                
                  if(qt3_value>500){
                    digitalWrite(ledpin, HIGH);
                    delay(10);
                    digitalWrite(ledpin,LOW);
                    delay(10);
                  }
                  
                }