/* * Copyright (c) 2010 by Cristian Maglie * Copyright (c) 2014 by Paul Stoffregen (Transaction API) * Copyright (c) 2014 by Matthijs Kooijman (SPISettings AVR) * Copyright (c) 2014 by Andrew J. Kroll (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 // SPI_HAS_TRANSACTION means SPI has beginTransaction(), endTransaction(), // usingInterrupt(), and SPISetting(clock, bitOrder, dataMode) #define SPI_HAS_TRANSACTION 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); // 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) { #ifdef SPI_AVR_EIMSK if (interruptMode == 1) { interruptSave = SPI_AVR_EIMSK; SPI_AVR_EIMSK &= ~interruptMask; } else #endif { interruptSave = SREG; cli(); } } #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 if (interruptMode == 1) { SPI_AVR_EIMSK = interruptSave; } 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