bradski58:
I know this is an old thread but thought I'd share my experience... in case anyone is considering using the ISD17xx.
...
Couldn't have put it better myself, so I didn't. 
I posted on "programming questions" as it was sorta a compiler thing of general interest maybe, but my point can be reiterated harmlessly here I hope.
BTW I love and approve of hijacking buttons if it can do what you need. But I think the fear people might have of SPI should be overcome.
The "ready_play_wait()" routine from above is flawed. It has a certain chance of failing to wait at all. byte3 is tested before it is received from the chip. All you needa do is change the while to a do/while.
I think this might have caused some heads to ache.
Here's a general ready_wait that works. No need for any delay(), but it does just waste time waiting.
void ready_wait()
{
int counter;
byte byte3;
counter = 0;
do {
counter++;
digitalWrite(SLAVESELECT, LOW);
spi_transfer(RD_STATUS);
spi_transfer(0x00);
byte3 = spi_transfer(0x00);
digitalWrite(SLAVESELECT, HIGH);
} while (byte3 << 7 != 128);
// Serial.println(counter);
// delay(100);
}
alto777