diff options
Diffstat (limited to 'libraries/SPI/SPI.cpp')
| -rw-r--r-- | libraries/SPI/SPI.cpp | 61 |
1 files changed, 41 insertions, 20 deletions
diff --git a/libraries/SPI/SPI.cpp b/libraries/SPI/SPI.cpp index ef13e2a..4bd72df 100644 --- a/libraries/SPI/SPI.cpp +++ b/libraries/SPI/SPI.cpp @@ -2,6 +2,7 @@ * 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) + * 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 @@ -14,6 +15,7 @@ SPIClass SPI; +uint8_t SPIClass::initialized = 0; uint8_t SPIClass::interruptMode = 0; uint8_t SPIClass::interruptMask = 0; uint8_t SPIClass::interruptSave = 0; @@ -23,32 +25,51 @@ uint8_t SPIClass::inTransactionFlag = 0; void SPIClass::begin() { - // Set SS to high so a connected chip will be "deselected" by default - digitalWrite(SS, HIGH); + 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 + 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); + // 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); + // 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); - // Set direction register for SCK and MOSI pin. - // MISO pin automatically overrides to INPUT. - // By doing this AFTER enabling SPI, we avoid accidentally - // clocking in a single bit since the lines go directly - // from "input" to SPI control. - // http://code.google.com/p/arduino/issues/detail?id=888 - pinMode(SCK, OUTPUT); - pinMode(MOSI, OUTPUT); + // Set direction register for SCK and MOSI pin. + // MISO pin automatically overrides to INPUT. + // By doing this AFTER enabling SPI, we avoid accidentally + // clocking in a single bit since the lines go directly + // from "input" to SPI control. + // http://code.google.com/p/arduino/issues/detail?id=888 + pinMode(SCK, OUTPUT); + pinMode(MOSI, OUTPUT); + } + initialized++; // reference count + SREG = sreg; } void SPIClass::end() { - SPCR &= ~_BV(SPE); + uint8_t sreg = SREG; + noInterrupts(); // Protect from a scheduler and prevent transactionBegin + // Decrease the reference counter + if (initialized) + initialized--; + // If there are no more references disable SPI + if (!initialized) { + SPCR &= ~_BV(SPE); + interruptMode = 0; + #ifdef SPI_TRANSACTION_MISMATCH_LED + inTransactionFlag = 0; + #endif + } + SREG = sreg; } // mapping of interrupt numbers to bits within SPI_AVR_EIMSK |