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Arduino Yun cheat sheet: Difference between revisions
→YUN と SPI と RX LED
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[http://forum.arduino.cc/index.php?topic=213389.0 Arduino Yun SPI on ICSP connector (try to connect to a isd 1760 shield)] | [http://forum.arduino.cc/index.php?topic=213389.0 Arduino Yun SPI on ICSP connector (try to connect to a isd 1760 shield)] | ||
[http://forum.arduino.cc/index.php?topic=223320.0 SPI on Yun] | [http://forum.arduino.cc/index.php?topic=223320.0 SPI on Yun] | ||
SPI Library によると、 | |||
<syntaxhighlight lang="cpp" enclose="div"> | |||
void SPIClass::begin() | |||
{ | |||
uint8_t sreg = SREG; | |||
noInterrupts(); // Protect from a scheduler and prevent transactionBegin | |||
if (!initialized) { | |||
// Set SS to high so a connected chip will be "deselected" by default | |||
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 | |||
// SPI operations). | |||
pinMode(SS, OUTPUT); | |||
// 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); | |||
<syntaxhighlight> | |||
試しに、 | |||
<syntaxhighlight lang="cpp" enclose="div"> | |||
SPI.begin(); | |||
digitalWrite(SS, LOW) | |||
<syntaxhighlight> | |||
してみたらどうなるか確認する。 | |||
== DS3234 の SQW と Alarm == | == DS3234 の SQW と Alarm == | ||