Errata

"...I'm running the SPI bus at a 1/16th multiplier, or 500 kHz."

It wasn't clear to me from the code in example 16-3 that the system clock on the atmega168 would be running at 8MHz without reseting the default clock of 1MHz. So 1/16th multiplier of 1MHz would be 65.2 kHz. Actually, I think the example code sets SPR1 in SPCR which from the data sheet means a divisor of 64.

Totally not a big deal. I'm sure the code runs fine because the 25LC256 has a max of 10MHz slave clock speed.

Note from the Author or Editor:
Two changes need to be made two the last paragraph on page 354.

In the second sentence, 8MHz should read 1MHz

In the next-to-last sentence, "running the SPI bus at 1/16th multiplier, or 500 kHz" should read "running the SPI bus at 1/64th multiplier, or 15.6 kHz".

The comments in the code listing for 25LC256.c in the initSPI() function should also be changed to read "div 64" rather than "div 16". The code itself is fine.

"1. Did you hook up AVCC? The ADC needs power, and it needs to be within around 0.6 V of the AVR’s VCC."

The datasheet for the Atmega168 says that AVCC must not differ more than ±0.3V from VCC...so I guess 0.6V is a little too much.

Note from the Author or Editor:
CORRECTED IN ATLAS

p.139 1st item on the list under ADC Gotchas

change to
"1. Did you hook up AVCC? The ADC needs power, and it needs to be within around +/- 0.3 V of the AVR’s VCC."

I believe there is a mistake in the ISR macro. The line:

if (bit_is_set(BUTTON_PIN, BUTTON)) {

should read

if (bit_is_clear(BUTTON_PIN, BUTTON)) {

for LED1 to turn ON and OFF when the button is pressed.

Note from the Author or Editor:
fixed in atlas, git repo

"Capacitors block DC current entirely, but
let higher and higher frequency AC current through
with less and less resistance."

DC means direct current and AC means alternating current so the usage of DC current or AC current would be a redundance of the word "current". This could appear throughout the book but this reader only noticed in this paragraph.

Note from the Author or Editor:
fixed in atlas

The "#define BV(bit)" should have "(1 << (bit))". The "()" around "bit" is missing.

Note from the Author or Editor:
Change to
#define BV(bit) (1 << (bit))


That's a good catch. In some circumstances, the difference could matter. Although I'm usually invoking such macro functions with "PB0" rather than with a complicated expression that could cause order-of-operations issues. Still, better safe than sorry.

Regarding "reminds you that they�re constants.", #defines are not constants. They often _evaluate_ to constants, but they *are* just textual replacements.

Note from the Author or Editor:
end of 3rd para

change "remind you that they're constants." to "remind you that they're not normal variables."

Aptitude is not installed by default on Ubuntu. Suggest using apt-get instead or directing readers to install aptitude.

Note from the Author or Editor:
Change first literal command line to begin with
"sudo apt-get install ..."

Suggest introducing a resistor where you instruct the reader to connect an LED across the AVR power pins, as it may blow the LED.

Note from the Author or Editor:
Change last sentence of first para in Troubleshooting to

A quick way to double-check is to put an LED with a series resistor across the AVR power pins, where you've got a capacitor.

Please change "previous examples" to "following examples"

Please change "gigabyte" to "gigabit"

In the listing, the local variable i is used before it is initialized. Maybe the AVR initializes the stack to 0 before running the program (guessing here?), but I would still explicitly initialize it to 0.

Note from the Author or Editor:
change line in example 4-1
just after // -------------- Inits -------------------- //
to:

uint8_t i =0;

The last paragraph reads: "Next, we want to send the value over the serial port to our computer. To make things easy, we convert the 10-bit number into a single 8-bit byte so that it�s easier to send over serial. A two-bit right-shift converts it down."

However, this refers to functionality that is not in the code in example 7-1, but to the later example 7-2 code.

Note from the Author or Editor:
He's right.

That entire final paragraph at the bottom of the page, beginning with "Next, we want to send the value over the serial port..." refers to an older version of the demo code.

If it's not too disruptive, strike the entire paragraph.

This section suggests using 'lsusb' on Mac, but 'lsusb' is not a standard Mac utility. However, a version is available here: https://github.com/jlhonora/lsusb

Note from the Author or Editor:
That's right.

For point #2 on p. 87, add (A Mac version of lsusb is at https://github.com/jlhonora/lsusb.)

In Example 4-3. "Using XOR to toggle a bit" there are two lines using the bitwise OR operator that should be using the XOR operator. The two lines are:
| = 0b11000111 // LED2 bit flipped on

and

| = 0b11000011 // LED2 bit flipped off

they should be:

^ = 0b11000111 // LED2 bit flipped on

and

^ = 0b11000011 // LED2 bit flipped off

The description in the paragraph beginning with "Hook up a button" and ending with "closer to zero volts or VCC." needs correction. Please replace this paragraph with:

Hook up a button to the supply voltage through a resistor on one side, and connect this junction to one of the AVR's pins that's configured for input. Connect the other side of the button to ground. When the button isn't pressed, the AVR will read the +VCC+ voltage, but when you do press the button the AVR's input pin will be grounded. Thus, by reading in the voltage on the pin, the AVR is able to detect whether or not you've pressed the button. Physical states are turned into voltage levels, which are in turn converted to logic values inside the chip.