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Arduino Yun cheat sheet: Difference between revisions
→YUN と SPI と RX LED
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{ | { | ||
uint8_t sreg = SREG; | uint8_t sreg = SREG; | ||
noInterrupts(); // Protect from a scheduler and prevent transactionBegin | noInterrupts(); // Protect from a scheduler and prevent transactionBegin | ||
if (!initialized) { | if (!initialized) { | ||
// Set SS to high so a connected chip will be "deselected" by default | // Set SS to high so a connected chip will be "deselected" by default | ||
uint8_t port = digitalPinToPort(SS); | uint8_t port = digitalPinToPort(SS); | ||
uint8_t bit = digitalPinToBitMask(SS); | uint8_t bit = digitalPinToBitMask(SS); | ||
volatile uint8_t *reg = portModeRegister(port); | volatile uint8_t *reg = portModeRegister(port); | ||
// if the SS pin is not already configured as an output | // if the SS pin is not already configured as an output | ||
// then set it high (to enable the internal pull-up resistor) | // then set it high (to enable the internal pull-up resistor) | ||
if(!(*reg & bit)){ | if(!(*reg & bit)){ | ||
digitalWrite(SS, HIGH); | digitalWrite(SS, HIGH); | ||
} | } | ||
// When the SS pin is set as OUTPUT, it can be used as | // When the SS pin is set as OUTPUT, it can be used as | ||
// a general purpose output port (it doesn't influence | // a general purpose output port (it doesn't influence | ||
// SPI operations). | // SPI operations). | ||
pinMode(SS, OUTPUT); | pinMode(SS, OUTPUT); | ||
// Warning: if the SS pin ever becomes a LOW INPUT then SPI | // Warning: if the SS pin ever becomes a LOW INPUT then SPI | ||
// automatically switches to Slave, so the data direction of | // automatically switches to Slave, so the data direction of | ||
// the SS pin MUST be kept as OUTPUT. | // the SS pin MUST be kept as OUTPUT. | ||
SPCR |= _BV(MSTR); | SPCR |= _BV(MSTR); | ||
SPCR |= _BV(SPE); | SPCR |= _BV(SPE); | ||