Errata

"...and when this is divided by the prescale factor of 64, each count of the timer will be 40,000 nanoseconds (62.5 * 64 = 40,000, which is four microseconds)."

Both instances of "40,000" should read "4,000". The value given finally in microseconds is correct.

PS: This book's document format (.mobi) doesn't give page numbers as I read the text -- this makes reporting errata via this Web form problematic.

Note from the Author or Editor:
the text on page 561 should read:

each count of the timer will be 4000 nanoseconds (62.5 * 64 = 4000, which is four microseconds).

Change "version 0018 through version 0020" to:

"version 0018 through version 0022"

The initial sketch provided for the LDR/Blink problem, at the top of page 16, causes a compilation error because "minDuration" and "maxDuration" have not been defined, as they are in subsequent sketches. Also, this first sketch includes the map function, which is supposed to be *introduced* in the 2nd LDR/Blink sketch.

Note from the Author or Editor:
The lines with the print and map functions (2nd and 3rd lines in the Solution sketch loop function) should be deleted. The download code is correct.

The last sentence of the first paragraph on page 16 should be changed from: " ... so the blink rate increases with light intensity."

to: " ... so the blink time increases with light intensity."

Under:

rate = map(rate, 200,800,minDuration, maxDuration); // convert to blink rate

add:

if(rate <minDuration)
rate = minDuration; // constrain the value

"Figure 1-8. Connections for a speaker with the LDR circuit" has connected the digital pin 9 to use a speaker but in the code still using the digital pin 13.

const int ledPin = 13;
...
pinMode(ledPin, OUTPUT);
...
void loop()
{
int sensorReading = analogRead(sensorPin); // read the analog input
int rate = map(sensorReading, 200,800,minDuration, maxDuration);
rate = rate / 100; // add this line for audio frequency
digitalWrite(ledPin, HIGH); // set the LED on
delay(rate); // wait duration dependent on light level
digitalWrite(ledPin, LOW); // set the LED off
delay(rate);
}

Note from the Author or Editor:
Pin 9 should be used instead of pin 13 when when connecting the speaker as per the diagram. The code in the download is correct.

Under:

rate = map(rate, 200,800,minDuration, maxDuration); // convert to blink rate

add:

if(rate <minDuration)
rate = minDuration; // constrain the value

Change:

const int ledPin = 9; // LED connected to digital pin 9

to:

const int ledPin = 9; // Speaker connected to digital pin 9

Two lines of code in loop() reference an undeclared variable "i" instead of the declared "index."

The 1st line with error: int val = digitalRead(inputPins[i]);

Corrected: int val = digitalRead(inputPins[index]);

The 2nd line with error: digitalWrite(ledPins[i], LOW);

Corrected: digitalWrite(ledPins[index], LOW);

Note from the Author or Editor:
the variable i in the loop function should be replaced by index.

The latest download code is correct.

add the following in new lines after Paul:

Mary
(Mary is repeated every 5 seconds)

The author describes a function and a way to avoid a temporary variable. Nevertheless, the function (sensorPercent) does use the "val" temporary variable, and does not declare it - the code would not compile. Since a temporary variable is still used, the example is kind of wrong, or confusing at best.

Book reads:

int sensorPercent(int pin)
{
val = analogRead(pin); // read the sensor (ranges from 0 to 1023)
return map(val,0,1023,0,100); // percent will ranges from 0 to 100.
}


It should read:

int sensorPercent(int pin)
{
int val = analogRead(pin); // read the sensor (ranges from 0 to 1023)
return map(val,0,1023,0,100); // percent will ranges from 0 to 100.
}

Note from the Author or Editor:
the following code on pages 40 and again on page 41 should be changed from:
val = analogRead(pin); // read the sensor (ranges from 0 to 1023)
to:
int val = analogRead(pin); // read the sensor (ranges from 0 to 1023)

the text:
The same functionality can be achieved without using a temporary variable
should be changed to:
The same functionality can be achieved without using the percent temporary variable

Where it says:

// functions with references must be declared before use
void swap(int &value1, int &value2);

Add a comment below "// functions with references must be declared before use" that says:

// in all but the latest Arduino releases

The first sentence should read "This sketch counts from zero to three by printing the value ..."

Note from the Author or Editor:
change the first sentence in the solution to:
"This sketch counts from zero to three by printing the value ..."

"pinMode(13, OUTPUT)" should be "pinMode(ledPin, OUTPUT)"

Note from the Author or Editor:
change
pinMode(13, OUTPUT)
to
pinMode(ledPin, OUTPUT)

The code will work as written as long as the ledPin constant is not changed. The download code has been updated.

Change:

These functions are used for rounding floating-point numbers; use floor to round down
and ceil to round up.

to:

These functions are used for rounding floating-point numbers; use floor(x) to get the largest integer that is not greater than x. Use ceil to get the smallest integer that is greater than x.

Add the following new paragraph to the discussion :

You can round to the nearest integer as follows:
if(floatValue > 0.0)
result = floor(floatValue + 0.5);
else
result = ceil(num - 0.5);

change:

which happens to be the value of the constant (DEG_TO_RAD is 0.017453292519...). So, you can use whichever approach you prefer.

to:

which happens to be the same value as the constant DEG_TO_RAD (0.017453292519...). Use whichever approach you prefer.

import java.awt.AWTException;
import java.awt.Robot;

need to be imported into the processing sketch ArduinoMouse.pde

Note from the Author or Editor:
the following imports need to be added in the Processing sketch:
import java.awt.AWTException;
import java.awt.Robot;

The download sketch has been corrected.

(The second edition already has these imports so no change is needed there)

comments in loop are reversed. should be...

digitalWrite(ledPin, HIGH); //turn led on

..

digitalWrite(ledPin, LOW); //turn led OFF

Note from the Author or Editor:
change:
digitalWrite(ledPin, HIGH); //turn led off
to
digitalWrite(ledPin, HIGH); //turn led on

change
digitalWrite(ledPin, LOW); //turn led on
to
digitalWrite(ledPin, LOW); //turn led off

(This change is also required in the text of the second edition, the download code for that edition has been corrected)

The text states that it uses floating-point calculation, but in fact, the calculation is done with 16-bit integer arithmetic and the resulting incorrect integer value is assigned to a floating-point variable.

If you run the code as presented in the text (and in the downloaded code as of April 16, 2011), you will discover that the printed values are all zero except in the case where the value from analogRead is 1023.

The correct results can be obtained of you change
[code]
float volts = (val / 1023) * referenceVolts; // calculate the ratio
[/code]

to

[code]
float volts = (val / 1024.0) * referenceVolts; // calculate the ratio
[/code]

Note from the Author or Editor:
The code for recipe 7.6 as printed will appear to function but because the first iteration of the second loop will be out of bounds an incorrect pin will be written. The code for Recipe 7.6 in the download is correct.

A minor cosmetic bug: The '.' and the fractional part are printed on a separate line rather than on the same line as the integer part.

Another cosmetic bug: Printing the fractional part does not show leading zeros.

An analogRead value of 673 results in a printed value of 3.61
An analogRead value of 723 shows a value 3.111

If I were just looking at the printout, not realizing what was happening, I might think that 3.61 is greater than 3.111



For me, a worse problem from a practical point of view is that, due to the presence of rather gross truncation error in the integer quotient 1023/5 and due to the fact that this is used in the quotient and modulo expressions to get the final printed results, the actual output can be tens of a percent off. Trying to interpret outputs given in thousandths of a volt or more when the actual errors can be half a volt or more doesn't make sense to me.

Note from the Author or Editor:
The code for Recipe 5.9 has been corrected in the download. Future editions of the print and PDF should use the corrected code.

Where it says:

long val = analogRead(batteryPin); // read the value from the sensor - note
val is a long int

fix comment wrap as follows:

long val = analogRead(batteryPin); // read the value from the sensor -
// note val is a long int

Change:

const int NBR_ELEMS = 10;
const int firstElement = 250; // first entry is 250 mV
const int interval = 250; // millivolts between each element
static int distance[TABLE_ENTRIES] = {150,140,130,100,60,50,40,35,30,25,20,15};

to:

const int TABLE_ENTRIES = 12; // The numebr of entries in the distance table
const int INTERVAL = 250; // millivolts seperating each table entry
//up to: .5 .75 1 1.5 2 2.5
static int distance[TABLE_ENTRIES] = { 150,140,130,100,60,50, 40,35,30,25,20,15 };
// distance in cm for each 250mv


And change:

if( mV > INTERVAL * TABLE_ENTRIES )

to:

if( mV > INTERVAL * TABLE_ENTRIES-1 )

Note from the Author or Editor:
The download code is correct

Where it says:

const int interval = 250; // millivolts separating each table entry
//up to: .5 .75 1 1.5 2 2.5

the spacing does not work for the second line of this comment. change the comment to read:

const int interval = 250; // millivolts separating each table entry
// table contains values from 0 up to 2.5 volts

Text before sketch should change from:

The following sketch turns on pin 2 when the temperature is above a threshold

to:

The following sketch triggers pin 13 when the temperature is above a threshold



And change 2nd line of code from:

const int outPin = 13; //2; // digital output pin

to:

const int outPin = 13; // digital output pin

Note from the Author or Editor:
The download code is correct

Figure reverses power leads to the RFID reader. In the diagram, the Arduino ground pin (GND) is connected to the RFID reader VCC (5v) and the Arduino 5v pin is connected to the RFID reader's GND.

Note from the Author or Editor:
The Arduino power connections are shown reversed in figure 6-13:
The RFID +5 pin should be connected to the Arduino 5V pin. The RFID Gnd pin should be connected to Arduino Gnd.

In sketch at bottom of page, change:

const int NbrLEDs = sizeof(ledPins) / sizof(ledPins[0];
const int ledPins[] = { 2, 3, 4, 5, 6, 7};

to:

const int ledPins[] = { 2, 3, 4, 5, 6, 7};
const int NbrLEDs = sizeof(ledPins) / sizeof(ledPins[0]);

Note from the Author or Editor:
This error is in the text, the download code is correct.

The value of NbrLEDS is 6.
The number of elements in the ledPins array is 6.

The for loop starts like this:

[code]
for (int led = NbrLEDs; led > 0; led--) {
digitalWrite(ledPins[led], HIGH);
[/code]

The first time through the loop, the array index is out of bounds.


Regards,

Dave

Note from the Author or Editor:
The code for recipe 7.6 as printed will work but because the first iteration of the second loop will be out of bounds an incorrect pin will be written.

The code for Recipe 7.6 in the download is correct.

Two errors based on the text(*):

1) Comment doesn't match code in the following line:

myservo.attach(9); // attaches the servo on pin 10 to the servo object


2) Second for loop inside loop() re-uses angle for the counter, but the following line of code uses 'pos' instead:

myservo.write(pos); // tell servo to go to position in variable 'pos'


(*) Code from Arduino [v0022] example Servo-Sweep sketch does not contain either of these issues.

Note from the Author or Editor:
Code for Recipe 8.1 in the download zip has been corrected.

int pos = 0; // variable to store the servo position

should be:

int angle = 0; // variable to store the servo position

Note from the Author or Editor:
The variable name should be changed from ps to angle. The current download code is correct.

in setup section:

pinMode(ledPin, OUTPUT);
should be:
pinMode(solenoidPin, OUTPUT);


in loop section:

digitalWrite(ledPin, LOW); // deactivates the solenoid
should be:
digitalWrite(solenoidPin, LOW); // deactivates the solenoid

Note from the Author or Editor:
Variable names should be changed as indicated, current download code is correct.

page 299 in the tip/suggestion/note, the description is not clear. pin 3 is not even in the picture, and 'another' 4.7k variable resistor is confusing because there are no 4.7k resistors in the diagram. I think that you meant to set up a voltage divider here, but it is not really explained clearly.

The voltage level (5 volts) is higher than audio amplifiers expect, so you may need to use another 4.7K variable resistor to reduce the voltage (connect one end to pin 3 and the other end to ground; then connect the slider to the tip of the jack plug).

Note from the Author or Editor:
The text at the bottom of page 298 should refer to Recipe 9.7, not 5.7

The note should say:
The voltage level (5 volts) is higher than audio amplifiers expect, so you may need to use a 4.7K variable resistor to reduce the level-
connect one end to pin 9 and the other end to ground, then connect
the slider to the tip of the jack plug. The barrel of the jack plug is connected to ground.

The common connections to the right-hand contacts of all of the switches should go to ground, not the junction of the resistor and the LED.

Note from the Author or Editor:
Figure 10-2 should be changed so the common connections to the right-hand contacts of all of the switches go to ground instead of the junction of the resistor and the LED.

The marquee function of manual scrolling for very long messages displays only "A message too lo" and would not scroll messages.
To work correctly, it needs only one code between delay() and while{}.

i.e.
delay(1000);
pos = 1; // add this code then the function work correctly
while(pos <= length - numCols)
{
......
}

Note from the Author or Editor:
The line setting pos to 1 prior to the while loop is missing from the code in the manuscript on page 344. The current download code has this corrected (see file chr11r4B.pde)

Where it says:

int pos;
for( pos = 0; pos < numCols; pos++)
lcd.print(text[pos]);
delay(1000); // allow time to read the first line before scrolling
while(pos <= length - numCols)

Before the "while(pos <= length - numCols)" line, add:

pos=1;

IC2_Master code

1. In Setup(), add
Serial.begin(9600);

2. In loop(), before
// send the data
add
c = Serial.receive(); // get the data

IC2_Slave code

1. Change
receiveEvent(int howMany);
to
receiveEvent();

Note from the Author or Editor:
1. In Setup(), add

Serial.begin(9600);

1. In setup(), change
Wire.begin();
to
I2CDebug(address);

2. On the previous page, second line from bottom, change
byte count;
to
byte count = 0;

3. It may be helpful to add a sentence explaining the connection between I2CDebugClass::write() and Print::println();

4. It may be cleaner to remove I2CDebugClass::begin(int id) and move its content into the constructor
I2CDebugClass::I2CDebugClass(int id);
begin(), with a return value, may have been used to simplify the addition of error checking in future, but such consideration has not been given to Wire.beginTransmission() or Wire.send().

Note from the Author or Editor:
In setup(), change:
Wire.begin();
to:
I2CDebug.begin(address);

on page 424 change
boolean I2CDebugClass::begin(int id)
{
I2CAddress = id; // save the slave's address
to:
boolean I2CDebugClass::begin(int id)
{
I2CAddress = id; // save the slave's address
count = 0;

Where it says:

void setup()
{
Wire.begin();
}

Change to:

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

Where it says:

boolean I2CDebugClass::begin(int id)
{
I2CAddress = id; // save the slave's address
count = 0;
I2CDebug(address); // join I2C bus (address optional for master)
return true;
}

Change to:

boolean I2CDebugClass::begin(int id)
{
I2CAddress = id; // save the slave's address
count = 0;
Wire.begin(); // join I2C bus (address optional for master)
return true;
}

In void setup(), remove:

Wire.begin();

and replace with:

I2CDebug.begin(address);

configureRadio(); must be replaced with configured = configureRadio(); . Also, on the previous page, "boolean configure = false;" can be changed to "boolean configure;", since "configure = configureRadio()" is executed in setup().

Great book, incidentally. At first I thought it was great because it made everything seem so simple. Then I realized using the Arduino really is simple!

Note from the Author or Editor:
on 438 change:
boolean configured = false;
to:
"boolean configured;"

On Page 439, change:
configureRadio(); // try again on page 439 should be changed to:
configured = configureRadio(); // try again"

The code in the download has been corrected.

Add a note after figure 14-8 saying:

Unlike Series 2, Series 1 XBee uses an external reference connected to 3.3v. Because the voltage on the slider of the pot can never be greater than the reference voltage, the resistor shown in Figure 14-7 is not needed.

The WebServerPost sketch does not function beyond serving the initial webpage.

Line 34 should be deleted, and the 'break' on line 61 should be moved to line 46. All will then be well.

Note from the Author or Editor:
The download code has been corrected and later editions have been revised

The boundary condition for the test should be:

if (brightness > 254)

not

if(brightness > 255)

Note from the Author or Editor:
The code will function as printed but 254 is the correct value for the boundry condition.

Change
if(brightness > 255)
to
if(brightness > 254)