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Fix for bug 888: Allow the SPI library to support different modes and other subtle issues #95

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Merged
merged 2 commits into from
Jun 6, 2012
Merged

Fix for bug 888: Allow the SPI library to support different modes and other subtle issues #95

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a41c123
fix SPI init issues as described http://code.google.com/p/arduino/iss…
gandrewstone Jun 5, 2012
4e8fffa
just change a comment to make more sense
gandrewstone Jun 6, 2012
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27 changes: 16 additions & 11 deletions libraries/SPI/SPI.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -14,27 +14,32 @@
SPIClass SPI;

void SPIClass::begin() {
// Set direction register for SCK and MOSI pin.
// MISO pin automatically overrides to INPUT.

// Set SS to high so a connected chip will be "deselected" by default
digitalWrite(SS, HIGH);

// When the SS pin is set as OUTPUT, it can be used as
// a general purpose output port (it doesn't influence
// SPI operations).

pinMode(SCK, OUTPUT);
pinMode(MOSI, OUTPUT);
pinMode(SS, OUTPUT);

digitalWrite(SCK, LOW);
digitalWrite(MOSI, LOW);
digitalWrite(SS, HIGH);

// Warning: if the SS pin ever becomes a LOW INPUT then SPI
// automatically switches to Slave, so the data direction of
// Warning: if the SS pin ever becomes a LOW INPUT then SPI
// automatically switches to Slave, so the data direction of
// the SS pin MUST be kept as OUTPUT.
SPCR |= _BV(MSTR);
SPCR |= _BV(SPE);

// Set direction register for SCK and MOSI pin.
// MISO pin automatically overrides to INPUT.
// By doing this AFTER enabling SPI, we avoid accidentally
// clocking in a single bit since the lines go directly
// from "input" to SPI control.
// http://code.google.com/p/arduino/issues/detail?id=888
pinMode(SCK, OUTPUT);
pinMode(MOSI, OUTPUT);
}


void SPIClass::end() {
SPCR &= ~_BV(SPE);
}
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