Time Flies – November 2009

Wow, looking back at my last post I see it was in October. November just flew by. Look for a couple of posts on activities that were squeezed in with everything else:

• FIOS Migration
• Garman GPS MAP 60 Acquisition
• Hacking around with Qt
• Arduino Robotics

Arduino – SD Card

This afternoon’s project was to connect an SD card to an Arduino to be able to record log information on the card for later retrieval using a PC.
For the project I used an SD/MMC Mini Board from Futurelec. Futurlec has a number of interesting products which are reasonably priced. The order took a little over a month given the fact that they didn’t have the board in stock and due to international shipping. During the wait the folks at Futurelec were quite responsive to my queries via email.
I was using an atmega328p chip powered at 3.3v with an 8mhz oscillator. This made things easier as I didn’t need to worry about voltage dividers between the microprocessor and the SD card. The hardware I used was rounded out with a 512mb Kodak SD Card I had laying around.

For software I used Bill Greiman’s fat16lib which performed flawlessly. I tested my project with fat16info, fat16write and fat16tail with version 17 of the Arduino IDE.
The only problem I had was that I missed that the SD/MMC Mini Board has two pins labeled CD. One is in fact pin 1 from the SD card while the other is Card Detect. Pin 1 from the SD card is clearly labeled as such but I missed it the first time and connected to the other CD.
The pinouts that I used are below for reference:

Arduino Pins	atmega328p Pins	Description	SD Card Pins	SD Description
10	16	ssel	1	cd/dat3
11	17	misi	2	cmd
13	19	sck	5	clk
12	18	miso	7	dat0
vcc 3.3v	vcc	vcc 3.3v	4	vcc 3.3v
gnd	gnd	gnd	3+6	gnd

I want to thank Bill Greiman for the great library he has put together. Also, my thanks to all of you who have posted information about your projects that helped me along.

Arduino – Serial Programmer

I decided that I wanted to experiment at programming the boot loader into chips myself. This started me down an interesting path.

After spending some time with Google and based on what I had around I decided that I would build a parallel programmer. For reference I used the directions on the Arduino site for a parallel programmer.

I modified the design to include a 28 pin dip socket so I would have something to put the chip in. After putting it all together and checking the connections with my trusty multi-media I couldn’t get it to work. I played around with it and with avrdude finally giving up after running out of ideas.

I went back to the drawing board and this time settled on a serial programmer that I could build with what I had on hand augmented with some parts from Radio Shack. Using this schematic I found in the adafruit forums.

I modified the design to us a 6 pin isp connector rather than the 10 pin in the schematic. I also built a simple chip cradle with a 6 pin isp connector and a power connector.

Once I had completed building both the programmer and the chip cradle and checking them out with the multi-meter I plugged it in and…

Nothing. Avrdude running on the PC didn’t see the atmega chip.

After a good nights rest and some more time with Google I determined that my problem was that, as I was using a pre-loaded Arduino chip that was set to us an external crystal/oscillator that I needed to add one to my chip cradle.

Given the mess of wires connecting all the pins together on the underside of the chip cradle this wasn’t easy. However, soon I had a chip cradle with a socket for an external oscillator. I plugged in the oscillator and…

Nothing. Once again avrdude running on the PC didn’t see the atmega chip. Looking at the oscillator and the socket it appeared that the legs of the oscillator might be thin enough not to be making contact. A slight wiggle of the oscillator and success!

I fixed this problem by soldering the oscillator to 3 pins which fit the socket better and it has been working ever since.

Below are several pictures of the finished product.

As usual I need to thank a number of good people who have been down this path before me for marking the way with their posted results. The adafruit, Sparkfun and Arduino forums were invaluable.

Serial Programmer with DB9 serial connector.

Serial Programmer with Sparkfun 3.3v/5v regulated power supply attached.

Chip cradle with oscillator

Arduino – Light from Sound

For this project I connected a microphone via an amplifier IC (LM386N) to the Arduino to drive the Sparkfun 8x8 multicolor LED Matrix. The LED was programmed to generate random ranges of colors based on the how loud the sound is.

This week I got in an order that I had been waiting for from Futurlec and therefore I am going to put this project on hold as I have some new components I want to test out.

I am posting this mostly so I will have a record of what I had done that I can come back to.

Below is the amplifier on the breadboard.

The code was hacked together quickly from a couple of examples.

//Define the "Normal" Colors
#define BLACK  0
#define RED  0xE0
#define GREEN  0x1C
#define BLUE  0x03
#define ORANGE  REDGREEN
#define MAGENTA  REDBLUE
#define TEAL  BLUEGREEN
#define WHITE (REDGREENBLUE)-0xA0

//Define the SPI Pin Numbers
#define DATAOUT 11//MOSI
#define DATAIN  12//MISO
#define SPICLOCK  13//sck
#define SLAVESELECT 10//ss

//Define the variables we'll need later in the program
char cleardisplay [64];
char n1 = 0;
char reddisplay[64];
char n2 = 0;
char greendisplay[64];
char n3 = 0;
char bluedisplay[64];
char n4 = 0;
char rdisplay[64];
char n5 = 0;

char color;
char clearcnt;

int val;
int amp;
int ledPin = 8;                // LED connected to digital pin 13

void setup() {
  //SPI Bus setup
  //Enable SPI HW, Master Mode, divide clock by 16    
  SPCR = (1<<SPE)(1<<MSTR)(1<<SPR1);    

  //SPI Bus setup

  //Set the pin modes for the RGB matrix
  pinMode(DATAOUT, OUTPUT);
  pinMode(DATAIN, INPUT);
  pinMode(SPICLOCK,OUTPUT);
  pinMode(SLAVESELECT,OUTPUT)

  //Make sure the RGB matrix is deactivated
  digitalWrite(SLAVESELECT,HIGH);

  for(int LED=0; LED<64; LED++){
    cleardisplay[LED] = 0;
    reddisplay[LED] = RED;
    greendisplay[LED] = GREEN;
    bluedisplay[LED] = BLUE;
  }
  color = 0;
  clearcnt = 0;
  pinMode(ledPin, OUTPUT);      // sets the digital pin as output 

  Serial.begin(9600);
  setdisplay(cleardisplay);
}

void loop() {
  val = analogRead(1);
  amp = (val >= 415) ? val - 415 : 415 - val;
  if (amp > 30) {
    digitalWrite(ledPin, HIGH);
    if (amp > 50) {
      if (color != RED) {
        rnddisplay(RED);
        color = RED;
      }
    } else if (amp > 40) {
      if (color != GREEN) {
        rnddisplay(GREEN);
        color = GREEN;
      }
    } else if (amp > 30) {
      if (color != BLUE) {
        rnddisplay(BLUE);
        color = BLUE;
      }
    }
    delay(250);
  } else {
    if (clearcnt > 1) {
      digitalWrite(ledPin, LOW);
      setdisplay(cleardisplay);
      color = 0;
      clearcnt = 0;
    } else {
      clearcnt++;
    }
  }
}

void rnddisplay(char color) {
  for(int LED=0; LED<64; LED++) {
    rdisplay[LED] = random(9) + color;
  }
  setdisplay(rdisplay);
}

void setdisplay(char displaybuf[64]) {
  digitalWrite(SLAVESELECT, LOW);
  for(int LED=0; LED<64; LED++){
    spi_transfer(displaybuf[LED]);
  }
  digitalWrite(SLAVESELECT, HIGH);
} 

//Use this command to send a single color value to the RGB matrix.
//NOTE: You must send 64 color values to the RGB matrix before it displays an image!

char spi_transfer(volatile char data) {
  SPDR = data;                    // Start the transmission
  while (!(SPSR & (1<<SPIF))) {   // Wait for the end of the transmission
  };
  return SPDR;                    // return the received byte
}

Arduino – Breadboard Arduino

As I have said in earlier posts I have been working with Arduino for the last several months. My latest project was to take the ATmega328 chip and assemble a very basic Arduino on a breadboard.

Using various sources found using Google I was able to assemble the breadboard Arduino in an evening and get it running a basic blink program.

I found several excellent sources for parts and information which I pass along below:

• NYU’s Tisch Interactive Telecommunications Program (ITP) program’s Tutorial for Setting up an Arduino on a breadboard.
• Sparkfun for the ATmega328 with the Arduino boot loader and a FTDI Basic Breakout – 5V.
• The todbot blog for the Arduino Chip Label.

Once I got all the parts and pieces the project was easy to assemble and get running. I was also able to combined this with the power supplies I built earlier to have a free standing finished product.

Simple 5V Regulated Power Supply Projects

Spent this Labor Day Weekend on a number of projects around the house but still had some time to undertake a couple of simple electronics projects.

The first project was to bread board a simple 5V regulated power supply using parts from Radio Shack and schematics from a couple of helpful websites found via Google.

The end result was a hybrid using the diagram below from http://www.tkk.fi/Misc/Electronics/circuits/psu_5v.html

and the schematic below from the Sparkfun Embeded Electronics Tutorial at http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=57

My design didn’t include the diode or the switch as the Sparkfun design does but did include the 0.1uF capacitor and the LED/resistor. The Sparkfun tutorial also included a diagram of the pinout for the 7805.

The second project was to assemble the Sparkfun Breadboard Power Supply 5V/3.3V (Part No: PRT-00114) http://www.sparkfun.com/commerce/product_info.php?products_id=114 which arrived during the week.

The assembly was a breeze and took less than an hour.

A word of thanks to the folks at Sparkfun for all the good information on their website, the wonderful products they make available and for the speed with which they get things out the door. I have now ordered from them twice and both times have used the USPS Priority shipping option and gotten my order the in three days of placing it.

Arduino – Amplified Speaker Project

I have been playing around with the Arduino for a couple of months. The Arduino is an inexpensive open-source electronics prototyping platform (http://www.arduino.cc/. The compilation below represents a very simple project to connect an amplified speaker to the Arduino.

The amplifier I used for this project is an LM386. The LM386 is a power amplifier designed for use in low voltage applications. It ant the other parts needed for this project , capacitors, resistors and a speaker, can be purchased at Radio Shack.

This example makes use of a Sound Hello World sketch by David Fowler to generate tones.

This also represents my first attempt at a circuit schematic using the freeware version of Eagle from CadSoft at http://www.cadsoft.de/.

My hope is that someone will find this useful and will be able to follow what I have done as I have done following the examples posted by others.

//Arduino Sound Hello World
//Created by David Fowler of uCHobby.com
//Define the I/O pin we will use for our sound output
#define SOUNDOUT_PIN 9

void setup(void){
  //Set the sound out pin to output mode
  pinMode(SOUNDOUT_PIN,OUTPUT);
}

void loop(void){
  //Generate sound by toggling the I/O pin High and Low
  //Generate a 1KHz tone. set the pin high for 500uS then
  //low for 500uS to make the period 1ms or 1KHz.

  //Set the pin high and delay for 1/2 a cycle of 1KHz, 500uS.
  digitalWrite(SOUNDOUT_PIN,HIGH);
  delayMicroseconds(500);

  //Set the pin low and delay for 1/2 a cycle of 1KHz, 500uS.
  digitalWrite(SOUNDOUT_PIN,LOW);
  delayMicroseconds(500);
}