Wk11: 2016/04/13

The assignments for wk11 were as below;

1. Measure something: add a sensor to a microcontroller board that you have designed and read it.

For final project, I would like to make "Lost Property Prevention Attachment", with GPS, motion sensor/accelerometer. However, handliing input device was totally new to me, so I decided to get familiar with embed programming with input device this week using "piezo" which can sensor vibration.

Piezo

First, I wanted to know the function of the sensor, so examined it using Arduino UNO without selfmade board. I found the very good tutorial which I was just trying to do; Arduino Tutorial: Knock sensor, so mainly proceed the test following this tutorial.

Arduino Test

As the picture above shows, I plugged the Piezo on the analog input pin number 0 and ground. Piezos have polarity, commercial devices are usually having a red and a black wires, and I connected the black one to ground and the red one to the input.

Test1: Serial Output

Next, I wanted to know the how the sensor output the value to the serial monitor, so wrote the very simple code set as below.

20160519_piezo_test.ino

/* Measure the value of Piezo
 */

int knockSensor = 0;               
byte val = 0;

void setup() {
 Serial.begin(9600);
}

void loop() {
  val = analogRead(knockSensor);     
  Serial.println(val);
  delay(100);  // we have to make a delay to avoid overloading the serial port
}

Then I could successfuly get the value which the sensor measured on serial monitor.

Piezo parameter on serial communication

Test2: Knock test

In addition to that, I wrote the "Knoch sensor" code with reference the previous tutorial, which posted the message "Knock!" to the serial monitor if some moment above set thereshold was added to the sensor.

20160519_knock_test.ino

// Knock Test

int ledPin = 13;
int knockSensor = 0;               
byte val = 0;
int statePin = LOW;
int THRESHOLD = 80;

void setup() {
 pinMode(ledPin, OUTPUT); 
 Serial.begin(9600);
}

void loop() {
  val = analogRead(knockSensor);     
  if (val >= THRESHOLD) {
    statePin = !statePin;
    digitalWrite(ledPin, statePin);
    Serial.println("Knock!");
  }
  delay(100);  // we have to make a delay to avoid overloading the serial port
}

What is 'Fabkit'?

'Fabkit' is an Arduino-compatible board designed by David Mells and based on an ATMEGA microcontrollers, which are more powerful microcontrollers provided by Amtel than ATtiny models. With this board, we can write code with an Arduino IDE (and all of its libraries).

Though the 'hello echo board' is one of the simplest boards that consist of an input (switch) and an output device, 'Fabkit' is a more capable board with more connectors and fitting boards with either simple or complicated input/output devices.

To make 'Fabkit', the following tutorials are raher vital that very useful.

• Fabkit i/o (aka Fabduino)
• Fabkit v.0.3-0.4
• FabKit v0.4 (also called Fabduino)

Milling, soldering and debugging

I straigtforward followed the tutorials above and procceded milling and soldering. I used Amtel: ATmega328P though it was different from the microcontroller that was used in the tutorials because there were not remaining stocks and Emma, who was our instructor, said that it can work tottaly same.

Though soldering the microcontroller was really difficult because the pin was incrediblly small, I was able to manage it and completed to make it.

Fabkit

Connecting with USBtinyISP

Though Fabkit can work almost same as Arduino, Fabkit have to be burned bootloader by USBtinyISP, then it was necessary to connect Fabkit to USBtinyISP. However, the configuration of their PIN were a bit different with each other, so I had to identify the correct pin configuration to connect.

First, I looked the connector configuration/blueprint of FabTinyISP and identified what the functions of each pins are.

Blueprint/Connector configuration of FabTinyISP

Next, I reserched the ATMEGA328P and schematic of Fabkit as below and managed to identified the pin configuration for 6 pin connectors, which was for connecting to FabTinyISP.

PIN configuration of ATMEGA328P from its datasheet

PIN configuration for 6pin connector

Finally, I successfuly connected Fabkit with FabTinyISP as below. If the connection is wrong, the parts on board sometimes get very hot and wrong, so correct connection is really important.

Fabkit connected to USBtinyISP

Burning bootloader

Next challenge was burning bootloader of Fabkit by FabTinyISP.

As I did in embedded programming week, the initialization and testing the conection was what to do first. Putting the UNIX command; avrdude -c usbtiny -p m328p to terminal, it tells us if the connection is clear or NOT.

This time, the problem occurred and somehow I was not able to clear this test... Though I asked Emma to help and we checked all the connection between the two, we could not identify the problem. Then, I could not help changing the microcontroller to new one. (Solderting again, it was really long way...)

Changin the microcontroller to new one

After substituting the microcontroller, I could pass the test in the end. The cause seemed that the previous microcontroller was something wrong.

Succcessful initializing/testing

In this case for burning bootloder, the exact setting was as below;
This setting is really important if you use wrong setting, it will not work.

• Board: "Arduino UNO"
• Programmer: "USBtinyISP"

Setting on Arduino

When you try to burn bootloader, you must keep pushing the 'RESET button' on the Fabkit board during the process. Then, I could burn bootloader in the end. Here, you can see the message of correct buring bootloader on Arduino command line .

Working test

Fabkit is compatible with Aruduino and can be programmed by Arduino IDE via FTDI cable. Then, I had to connect Fabkit with FTDI cable correctlly cheking the pin configuration of FTDI cable as below.

PIN configuration of FTDI cable

Next, I implmented the simple code of blinking test as below to check if Fabkit were wroking correctlly. I pointed the PIN 13 as blinking one because it was connected to LED on the circuit(please refer the blueprint above.)

20160519_blinking_test.ino

void setup() {
  // initialize digital pin 13 as an output.
  pinMode(13, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);              // wait for a second
  digitalWrite(13, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);              // wait for a second
}

The test went well as the video below. It worked completely same as my Aruduino UNO! Then, I fineshied all preparation for enojoying programming on Fabkit.

Blinking test on Fabkit

I implmented the same code as the one on Arduino test; '20160519_piezo_test.ino'. I paid attention to the connection between the board and piezo checking the pin configuration of Fabkit. I plugged other wires to the same hole in which ones of piezo were plugged because the wires of piezo was too thin to keep the connection stable.

Fabkit with piezo

Writing the programme on Fabkit, I got the same result as I got on Arduino test on serial monitor, and completed the assignments of input device in the end.

The result on serial monitor

For the assignments this weeek, I decided to make accelerometer board, which I could use for my final project: lost property prevention device sensoring the accleration when someone tried to steal my items.

Having discussion with Emma, our local instructor, I chose 3-Axis Accelerometer: MXR9150MZ. For my project this week, I read a lot of time this past student's page: Vincent Chow: Collecting Sleep Data via a 3-Axis Accelerometer.

3-Axis Accelerometer: MXR9150MZ

Design the board

First, we made a lough sketch of the schematic with a lot of help by Emma. The challenge was that I had to add reguralor to decrease the voltage because the appropriate voltage for Fabkit was mainly 5V, however, that for MXR9150 was 2.7V to 3.6V according to the datasheet of MXR9150MZ

Therefore, I added a 3.3V regulator to down the voltage from 5V to 3.3V and two capacitors to stabilize the current as the sketch below with reffering the datasheet of regulator.

the sketch of the accelerometer board

Adding MXR9150 to EAGLE

Next, before starting to write the schematic on EAGLE, I had to add MXR9150 to EAGLE library because there were no sketch on the internet. During the whole process, I mainly referred these useful sites below.

• Cadsoft Eagle Tutorial: Creating New Parts
• Qiita: How to add new parts to EAGLE (JAPANESE)

The process was as below;

1. First, write the symbol of MXR9150
   

   Symbol of MXR9150

   
   
   
2. write the board for it making it corresponded with the pin configuration on its datasheet.
   
   
   

   Symbol of MXR9150

   
   
   
3. Connect the virtual symbol and the physical board
   

   Connecting the symbol and the borad

Finally, I successfuly added the parts to EAGLE library.lol

Designing the board on Eagle

Following process was really straigtforward. First, I put parts' symbol to the sketch and connected them with each other on EAGLE, following the lough sketch above, and then made the schematic as below.

20160602_accel_board.sch

20160602_accel_board.brd

Finally, I exported PNG file for tracing and cutting by modela as below and finished the designing part.

accel_trace.png

accel_cutting.png

Soldering the parts to the board

The soldering part was also finished straigtforward. Here is the accelerometer board which I made.

Accelerometer board

Writing the code and testing

First, I connected the new accelerometer board to Fabkit, which I made previously. As the output of parameter which accelerometer can read was analog output, I used analog pin on Fabkit and connect them with each other as below.

PIN configuration of two boards

Next, I wrote the test code on Arduino for checking if the accelerometer were working correctlly or NOT as below.

20160607_accel_test.ino

#include 

int pin_x = 17;
int pin_y = 18;
int pin_z = 19;
byte val_x = 0;
byte val_y = 0;
byte val_z = 0;

void setup() {
  Serial.begin(9600);
  pinMode(pin_x, INPUT);
  pinMode(pin_y, INPUT);
  pinMode(pin_z, INPUT);
}

void loop() {
  val_x = analogRead(pin_x);     
  val_y = analogRead(pin_y);     
  val_z = analogRead(pin_z);     

  Serial.print(val_x);
  Serial.print(", ");
  Serial.print(val_y);
  Serial.print(", ");
  Serial.print(val_z);
  Serial.print(", ");
  Serial.println("");

  delay(100);
}

Then finally, I was able to read the output of the accelerometer on the serial monitor of Arduino as below, and successfuly made the baord.

The output on the serial monitor on Aruduino