SPI Transactions for AVR

2 files changed, 324 insertions, 44 deletions

diff --git a/libraries/SPI/SPI.cpp b/libraries/SPI/SPI.cpp
index 5e48073..9a7a400 100644
--- a/libraries/SPI/SPI.cpp
+++ b/libraries/SPI/SPI.cpp
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2010 by Cristian Maglie <c.maglie@bug.st>
+ * Copyright (c) 2014 by Paul Stoffregen <paul@pjrc.com> (Transaction API)
  * SPI Master library for arduino.
  *
  * This file is free software; you can redistribute it and/or modify
@@ -8,13 +9,20 @@
  * published by the Free Software Foundation.
  */
 
-#include "pins_arduino.h"
 #include "SPI.h"
+#include "pins_arduino.h"
 
 SPIClass SPI;
 
-void SPIClass::begin() {
+uint8_t SPIClass::interruptMode = 0;
+uint8_t SPIClass::interruptMask = 0;
+uint8_t SPIClass::interruptSave = 0;
+#ifdef SPI_TRANSACTION_MISMATCH_LED
+uint8_t SPIClass::inTransactionFlag = 0;
+#endif
 
+void SPIClass::begin()
+{
   // Set SS to high so a connected chip will be "deselected" by default
   digitalWrite(SS, HIGH);
 
@@ -39,28 +47,86 @@ void SPIClass::begin() {
   pinMode(MOSI, OUTPUT);
 }
 
-
 void SPIClass::end() {
   SPCR &= ~_BV(SPE);
 }
 
-void SPIClass::setBitOrder(uint8_t bitOrder)
-{
-  if(bitOrder == LSBFIRST) {
-    SPCR |= _BV(DORD);
-  } else {
-    SPCR &= ~(_BV(DORD));
-  }
-}
+// mapping of interrupt numbers to bits within SPI_AVR_EIMSK
+#if defined(__AVR_ATmega32U4__)
+  #define SPI_INT0_MASK  (1<<INT0)
+  #define SPI_INT1_MASK  (1<<INT1)
+  #define SPI_INT2_MASK  (1<<INT2)
+  #define SPI_INT3_MASK  (1<<INT3)
+  #define SPI_INT4_MASK  (1<<INT6)
+#elif defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB1286__)
+  #define SPI_INT0_MASK  (1<<INT0)
+  #define SPI_INT1_MASK  (1<<INT1)
+  #define SPI_INT2_MASK  (1<<INT2)
+  #define SPI_INT3_MASK  (1<<INT3)
+  #define SPI_INT4_MASK  (1<<INT4)
+  #define SPI_INT5_MASK  (1<<INT5)
+  #define SPI_INT6_MASK  (1<<INT6)
+  #define SPI_INT7_MASK  (1<<INT7)
+#elif defined(EICRA) && defined(EICRB) && defined(EIMSK)
+  #define SPI_INT0_MASK  (1<<INT4)
+  #define SPI_INT1_MASK  (1<<INT5)
+  #define SPI_INT2_MASK  (1<<INT0)
+  #define SPI_INT3_MASK  (1<<INT1)
+  #define SPI_INT4_MASK  (1<<INT2)
+  #define SPI_INT5_MASK  (1<<INT3)
+  #define SPI_INT6_MASK  (1<<INT6)
+  #define SPI_INT7_MASK  (1<<INT7)
+#else
+  #ifdef INT0
+  #define SPI_INT0_MASK  (1<<INT0)
+  #endif
+  #ifdef INT1
+  #define SPI_INT1_MASK  (1<<INT1)
+  #endif
+  #ifdef INT2
+  #define SPI_INT2_MASK  (1<<INT2)
+  #endif
+#endif
 
-void SPIClass::setDataMode(uint8_t mode)
+void SPIClass::usingInterrupt(uint8_t interruptNumber)
 {
-  SPCR = (SPCR & ~SPI_MODE_MASK) | mode;
-}
+  uint8_t mask;
 
-void SPIClass::setClockDivider(uint8_t rate)
-{
-  SPCR = (SPCR & ~SPI_CLOCK_MASK) | (rate & SPI_CLOCK_MASK);
-  SPSR = (SPSR & ~SPI_2XCLOCK_MASK) | ((rate >> 2) & SPI_2XCLOCK_MASK);
+  if (interruptMode > 1) return;
+
+  noInterrupts();
+  switch (interruptNumber) {
+  #ifdef SPI_INT0_MASK
+  case 0: mask = SPI_INT0_MASK; break;
+  #endif
+  #ifdef SPI_INT1_MASK
+  case 1: mask = SPI_INT1_MASK; break;
+  #endif
+  #ifdef SPI_INT2_MASK
+  case 2: mask = SPI_INT2_MASK; break;
+  #endif
+  #ifdef SPI_INT3_MASK
+  case 3: mask = SPI_INT3_MASK; break;
+  #endif
+  #ifdef SPI_INT4_MASK
+  case 4: mask = SPI_INT4_MASK; break;
+  #endif
+  #ifdef SPI_INT5_MASK
+  case 5: mask = SPI_INT5_MASK; break;
+  #endif
+  #ifdef SPI_INT6_MASK
+  case 6: mask = SPI_INT6_MASK; break;
+  #endif
+  #ifdef SPI_INT7_MASK
+  case 7: mask = SPI_INT7_MASK; break;
+  #endif
+  default:
+    interruptMode = 2;
+    interrupts();
+    return;
+  }
+  interruptMode = 1;
+  interruptMask |= mask;
+  interrupts();
 }
 
diff --git a/libraries/SPI/SPI.h b/libraries/SPI/SPI.h
index f647d5c..962100b 100644
--- a/libraries/SPI/SPI.h
+++ b/libraries/SPI/SPI.h
@@ -1,5 +1,7 @@
 /*
  * Copyright (c) 2010 by Cristian Maglie <c.maglie@bug.st>
+ * Copyright (c) 2014 by Paul Stoffregen <paul@pjrc.com> (Transaction API)
+ * Copyright (c) 2014 by Matthijs Kooijman <matthijs@stdin.nl> (SPISettings AVR)
  * SPI Master library for arduino.
  *
  * This file is free software; you can redistribute it and/or modify
@@ -11,9 +13,24 @@
 #ifndef _SPI_H_INCLUDED
 #define _SPI_H_INCLUDED
 
-#include <stdio.h>
 #include <Arduino.h>
-#include <avr/pgmspace.h>
+
+// 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 a 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
@@ -22,7 +39,6 @@
 #define SPI_CLOCK_DIV2 0x04
 #define SPI_CLOCK_DIV8 0x05
 #define SPI_CLOCK_DIV32 0x06
-//#define SPI_CLOCK_DIV64 0x07
 
 #define SPI_MODE0 0x00
 #define SPI_MODE1 0x04
@@ -33,38 +49,236 @@
 #define SPI_CLOCK_MASK 0x03  // SPR1 = bit 1, SPR0 = bit 0 on SPCR
 #define SPI_2XCLOCK_MASK 0x01  // SPI2X = bit 0 on SPSR
 
-class SPIClass {
+// 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:
-  inline static byte transfer(byte _data);
+  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
 
-  // SPI Configuration methods
+    // 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;
 
-  inline static void attachInterrupt();
-  inline static void detachInterrupt(); // Default
+    // 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++;
+      }
+    }
 
-  static void begin(); // Default
-  static void end();
+    // Compensate for the duplicate fosc/64
+    if (clockDiv == 6)
+    clockDiv = 7;
 
-  static void setBitOrder(uint8_t);
-  static void setDataMode(uint8_t);
-  static void setClockDivider(uint8_t);
+    // 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;
 };
 
-extern SPIClass SPI;
 
-byte SPIClass::transfer(byte _data) {
-  SPDR = _data;
-  while (!(SPSR & _BV(SPIF)))
-    ;
-  return SPDR;
-}
+class SPIClass {
+public:
+  // Initialize the SPI library
+  static void begin();
+
+  // If SPI is to 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;
+    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;
+      while (!(SPSR & _BV(SPIF))) ;
+      out.msb = SPDR;
+      SPDR = in.lsb;
+      while (!(SPSR & _BV(SPIF))) ;
+      out.lsb = SPDR;
+    } else {
+      SPDR = in.lsb;
+      while (!(SPSR & _BV(SPIF))) ;
+      out.lsb = SPDR;
+      SPDR = in.msb;
+      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;
+      }
+    }
+  }
 
-void SPIClass::attachInterrupt() {
-  SPCR |= _BV(SPIE);
-}
+  // 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); }
 
-void SPIClass::detachInterrupt() {
-  SPCR &= ~_BV(SPIE);
-}
+private:
+  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