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Do not influence state of SS if it's already been set to an output previously, e.g. by user sketch

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squashes and closes PR #2659
This commit is contained in:
Victor Aprea 2015-02-15 17:56:48 -05:00 committed by Martino Facchin
parent 375013173d
commit 0e898d5e03
1 changed files with 9 additions and 1 deletions
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10
hardware/arduino/avr/libraries/SPI/SPI.cpp
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@ -29,7 +29,15 @@ void SPIClass::begin()
noInterrupts(); // Protect from a scheduler and prevent transactionBegin
if (!initialized) {
// Set SS to high so a connected chip will be "deselected" by default
digitalWrite(SS, HIGH);
uint8_t port = digitalPinToPort(SS);
uint8_t bit = digitalPinToBitMask(SS);
volatile uint8_t *reg = portModeRegister(port);
// if the SS pin is not already configured as an output
// then set it high (to enable the internal pull-up resistor)
if(!(*reg & bit)){
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