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+/*
+ * Copyright (c) 2010 by Cristian Maglie <c.maglie@arduino.cc>
+ * Copyright (c) 2014 by Paul Stoffregen <paul@pjrc.com> (Transaction API)
+ * Copyright (c) 2014 by Matthijs Kooijman <matthijs@stdin.nl> (SPISettings AVR)
+ * Copyright (c) 2014 by Andrew J. Kroll <xxxajk@gmail.com> (atomicity fixes)
+ * SPI Master library for arduino.
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _SPI_H_INCLUDED
+#define _SPI_H_INCLUDED
+
+#include <Arduino.h>
+
+// SPI_HAS_TRANSACTION means SPI has beginTransaction(), endTransaction(),
+// usingInterrupt(), and SPISetting(clock, bitOrder, dataMode)
+#define SPI_HAS_TRANSACTION 1
+
+// SPI_HAS_NOTUSINGINTERRUPT means that SPI has notUsingInterrupt() method
+#define SPI_HAS_NOTUSINGINTERRUPT 1
+
+// SPI_ATOMIC_VERSION means that SPI has atomicity fixes and what version.
+// This way when there is a bug fix you can check this define to alert users
+// of your code if it uses better version of this library.
+// This also implies everything that SPI_HAS_TRANSACTION as documented above is
+// available too.
+#define SPI_ATOMIC_VERSION 1
+
+// Uncomment this line to add detection of mismatched begin/end transactions.
+// A mismatch occurs if other libraries fail to use SPI.endTransaction() for
+// each SPI.beginTransaction(). Connect an LED to this pin. The LED will turn
+// on if any mismatch is ever detected.
+//#define SPI_TRANSACTION_MISMATCH_LED 5
+
+#ifndef LSBFIRST
+#define LSBFIRST 0
+#endif
+#ifndef MSBFIRST
+#define MSBFIRST 1
+#endif
+
+#define SPI_CLOCK_DIV4 0x00
+#define SPI_CLOCK_DIV16 0x01
+#define SPI_CLOCK_DIV64 0x02
+#define SPI_CLOCK_DIV128 0x03
+#define SPI_CLOCK_DIV2 0x04
+#define SPI_CLOCK_DIV8 0x05
+#define SPI_CLOCK_DIV32 0x06
+
+#define SPI_MODE0 0x00
+#define SPI_MODE1 0x04
+#define SPI_MODE2 0x08
+#define SPI_MODE3 0x0C
+
+#define SPI_MODE_MASK 0x0C // CPOL = bit 3, CPHA = bit 2 on SPCR
+#define SPI_CLOCK_MASK 0x03 // SPR1 = bit 1, SPR0 = bit 0 on SPCR
+#define SPI_2XCLOCK_MASK 0x01 // SPI2X = bit 0 on SPSR
+
+// define SPI_AVR_EIMSK for AVR boards with external interrupt pins
+#if defined(EIMSK)
+ #define SPI_AVR_EIMSK EIMSK
+#elif defined(GICR)
+ #define SPI_AVR_EIMSK GICR
+#elif defined(GIMSK)
+ #define SPI_AVR_EIMSK GIMSK
+#endif
+
+class SPISettings {
+public:
+ SPISettings(uint32_t clock, uint8_t bitOrder, uint8_t dataMode) {
+ if (__builtin_constant_p(clock)) {
+ init_AlwaysInline(clock, bitOrder, dataMode);
+ } else {
+ init_MightInline(clock, bitOrder, dataMode);
+ }
+ }
+ SPISettings() {
+ init_AlwaysInline(4000000, MSBFIRST, SPI_MODE0);
+ }
+private:
+ void init_MightInline(uint32_t clock, uint8_t bitOrder, uint8_t dataMode) {
+ init_AlwaysInline(clock, bitOrder, dataMode);
+ }
+ void init_AlwaysInline(uint32_t clock, uint8_t bitOrder, uint8_t dataMode)
+ __attribute__((__always_inline__)) {
+ // Clock settings are defined as follows. Note that this shows SPI2X
+ // inverted, so the bits form increasing numbers. Also note that
+ // fosc/64 appears twice
+ // SPR1 SPR0 ~SPI2X Freq
+ // 0 0 0 fosc/2
+ // 0 0 1 fosc/4
+ // 0 1 0 fosc/8
+ // 0 1 1 fosc/16
+ // 1 0 0 fosc/32
+ // 1 0 1 fosc/64
+ // 1 1 0 fosc/64
+ // 1 1 1 fosc/128
+
+ // We find the fastest clock that is less than or equal to the
+ // given clock rate. The clock divider that results in clock_setting
+ // is 2 ^^ (clock_div + 1). If nothing is slow enough, we'll use the
+ // slowest (128 == 2 ^^ 7, so clock_div = 6).
+ uint8_t clockDiv;
+
+ // When the clock is known at compiletime, use this if-then-else
+ // cascade, which the compiler knows how to completely optimize
+ // away. When clock is not known, use a loop instead, which generates
+ // shorter code.
+ if (__builtin_constant_p(clock)) {
+ if (clock >= F_CPU / 2) {
+ clockDiv = 0;
+ } else if (clock >= F_CPU / 4) {
+ clockDiv = 1;
+ } else if (clock >= F_CPU / 8) {
+ clockDiv = 2;
+ } else if (clock >= F_CPU / 16) {
+ clockDiv = 3;
+ } else if (clock >= F_CPU / 32) {
+ clockDiv = 4;
+ } else if (clock >= F_CPU / 64) {
+ clockDiv = 5;
+ } else {
+ clockDiv = 6;
+ }
+ } else {
+ uint32_t clockSetting = F_CPU / 2;
+ clockDiv = 0;
+ while (clockDiv < 6 && clock < clockSetting) {
+ clockSetting /= 2;
+ clockDiv++;
+ }
+ }
+
+ // Compensate for the duplicate fosc/64
+ if (clockDiv == 6)
+ clockDiv = 7;
+
+ // Invert the SPI2X bit
+ clockDiv ^= 0x1;
+
+ // Pack into the SPISettings class
+ spcr = _BV(SPE) | _BV(MSTR) | ((bitOrder == LSBFIRST) ? _BV(DORD) : 0) |
+ (dataMode & SPI_MODE_MASK) | ((clockDiv >> 1) & SPI_CLOCK_MASK);
+ spsr = clockDiv & SPI_2XCLOCK_MASK;
+ }
+ uint8_t spcr;
+ uint8_t spsr;
+ friend class SPIClass;
+};
+
+
+class SPIClass {
+public:
+ // Initialize the SPI library
+ static void begin();
+
+ // If SPI is used from within an interrupt, this function registers
+ // that interrupt with the SPI library, so beginTransaction() can
+ // prevent conflicts. The input interruptNumber is the number used
+ // with attachInterrupt. If SPI is used from a different interrupt
+ // (eg, a timer), interruptNumber should be 255.
+ static void usingInterrupt(uint8_t interruptNumber);
+ // And this does the opposite.
+ static void notUsingInterrupt(uint8_t interruptNumber);
+ // Note: the usingInterrupt and notUsingInterrupt functions should
+ // not to be called from ISR context or inside a transaction.
+ // For details see:
+ // https://github.com/arduino/Arduino/pull/2381
+ // https://github.com/arduino/Arduino/pull/2449
+
+ // Before using SPI.transfer() or asserting chip select pins,
+ // this function is used to gain exclusive access to the SPI bus
+ // and configure the correct settings.
+ inline static void beginTransaction(SPISettings settings) {
+ if (interruptMode > 0) {
+ uint8_t sreg = SREG;
+ noInterrupts();
+
+ #ifdef SPI_AVR_EIMSK
+ if (interruptMode == 1) {
+ interruptSave = SPI_AVR_EIMSK;
+ SPI_AVR_EIMSK &= ~interruptMask;
+ SREG = sreg;
+ } else
+ #endif
+ {
+ interruptSave = sreg;
+ }
+ }
+
+ #ifdef SPI_TRANSACTION_MISMATCH_LED
+ if (inTransactionFlag) {
+ pinMode(SPI_TRANSACTION_MISMATCH_LED, OUTPUT);
+ digitalWrite(SPI_TRANSACTION_MISMATCH_LED, HIGH);
+ }
+ inTransactionFlag = 1;
+ #endif
+
+ SPCR = settings.spcr;
+ SPSR = settings.spsr;
+ }
+
+ // Write to the SPI bus (MOSI pin) and also receive (MISO pin)
+ inline static uint8_t transfer(uint8_t data) {
+ SPDR = data;
+ /*
+ * The following NOP introduces a small delay that can prevent the wait
+ * loop form iterating when running at the maximum speed. This gives
+ * about 10% more speed, even if it seems counter-intuitive. At lower
+ * speeds it is unnoticed.
+ */
+ asm volatile("nop");
+ while (!(SPSR & _BV(SPIF))) ; // wait
+ return SPDR;
+ }
+ inline static uint16_t transfer16(uint16_t data) {
+ union { uint16_t val; struct { uint8_t lsb; uint8_t msb; }; } in, out;
+ in.val = data;
+ if (!(SPCR & _BV(DORD))) {
+ SPDR = in.msb;
+ asm volatile("nop"); // See transfer(uint8_t) function
+ while (!(SPSR & _BV(SPIF))) ;
+ out.msb = SPDR;
+ SPDR = in.lsb;
+ asm volatile("nop");
+ while (!(SPSR & _BV(SPIF))) ;
+ out.lsb = SPDR;
+ } else {
+ SPDR = in.lsb;
+ asm volatile("nop");
+ while (!(SPSR & _BV(SPIF))) ;
+ out.lsb = SPDR;
+ SPDR = in.msb;
+ asm volatile("nop");
+ while (!(SPSR & _BV(SPIF))) ;
+ out.msb = SPDR;
+ }
+ return out.val;
+ }
+ inline static void transfer(void *buf, size_t count) {
+ if (count == 0) return;
+ uint8_t *p = (uint8_t *)buf;
+ SPDR = *p;
+ while (--count > 0) {
+ uint8_t out = *(p + 1);
+ while (!(SPSR & _BV(SPIF))) ;
+ uint8_t in = SPDR;
+ SPDR = out;
+ *p++ = in;
+ }
+ while (!(SPSR & _BV(SPIF))) ;
+ *p = SPDR;
+ }
+ // After performing a group of transfers and releasing the chip select
+ // signal, this function allows others to access the SPI bus
+ inline static void endTransaction(void) {
+ #ifdef SPI_TRANSACTION_MISMATCH_LED
+ if (!inTransactionFlag) {
+ pinMode(SPI_TRANSACTION_MISMATCH_LED, OUTPUT);
+ digitalWrite(SPI_TRANSACTION_MISMATCH_LED, HIGH);
+ }
+ inTransactionFlag = 0;
+ #endif
+
+ if (interruptMode > 0) {
+ #ifdef SPI_AVR_EIMSK
+ uint8_t sreg = SREG;
+ #endif
+ noInterrupts();
+ #ifdef SPI_AVR_EIMSK
+ if (interruptMode == 1) {
+ SPI_AVR_EIMSK = interruptSave;
+ SREG = sreg;
+ } else
+ #endif
+ {
+ SREG = interruptSave;
+ }
+ }
+ }
+
+ // Disable the SPI bus
+ static void end();
+
+ // This function is deprecated. New applications should use
+ // beginTransaction() to configure SPI settings.
+ inline static void setBitOrder(uint8_t bitOrder) {
+ if (bitOrder == LSBFIRST) SPCR |= _BV(DORD);
+ else SPCR &= ~(_BV(DORD));
+ }
+ // This function is deprecated. New applications should use
+ // beginTransaction() to configure SPI settings.
+ inline static void setDataMode(uint8_t dataMode) {
+ SPCR = (SPCR & ~SPI_MODE_MASK) | dataMode;
+ }
+ // This function is deprecated. New applications should use
+ // beginTransaction() to configure SPI settings.
+ inline static void setClockDivider(uint8_t clockDiv) {
+ SPCR = (SPCR & ~SPI_CLOCK_MASK) | (clockDiv & SPI_CLOCK_MASK);
+ SPSR = (SPSR & ~SPI_2XCLOCK_MASK) | ((clockDiv >> 2) & SPI_2XCLOCK_MASK);
+ }
+ // These undocumented functions should not be used. SPI.transfer()
+ // polls the hardware flag which is automatically cleared as the
+ // AVR responds to SPI's interrupt
+ inline static void attachInterrupt() { SPCR |= _BV(SPIE); }
+ inline static void detachInterrupt() { SPCR &= ~_BV(SPIE); }
+
+private:
+ static uint8_t initialized;
+ static uint8_t interruptMode; // 0=none, 1=mask, 2=global
+ static uint8_t interruptMask; // which interrupts to mask
+ static uint8_t interruptSave; // temp storage, to restore state
+ #ifdef SPI_TRANSACTION_MISMATCH_LED
+ static uint8_t inTransactionFlag;
+ #endif
+};
+
+extern SPIClass SPI;
+
+#endif
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