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fix SPI init issues as described http://code.google.com/p/arduino/issues/detail?id=888. Tested using qt1110 (mode 3) on a mega and WS5100 (webserver example sketch) chips on a etherten

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This commit is contained in:
Andrew Stone 2012-06-05 15:45:51 -04:00
parent 308d907694
commit a41c1233ba
1 changed files with 18 additions and 11 deletions
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25
libraries/SPI/SPI.cpp
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@ -14,27 +14,34 @@
SPIClass SPI;
void SPIClass::begin() {
// Set direction register for SCK and MOSI pin.
// MISO pin automatically overrides to INPUT.
// Set SS to high because many users use this as chip-select
// and most chips "select" when SS is high. If your chip
// does not, you can set it back to LOW after begin() is called.
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
// 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);
}