diff options
Diffstat (limited to 'libraries/Wire')
| -rwxr-xr-x | libraries/Wire/Wire.cpp | 43 | ||||
| -rwxr-xr-x | libraries/Wire/Wire.h | 5 | ||||
| -rw-r--r-- | libraries/Wire/utility/twi.c | 75 | ||||
| -rwxr-xr-x | libraries/Wire/utility/twi.h | 4 |
4 files changed, 111 insertions, 16 deletions
diff --git a/libraries/Wire/Wire.cpp b/libraries/Wire/Wire.cpp index d83f478..4e7a17c 100755 --- a/libraries/Wire/Wire.cpp +++ b/libraries/Wire/Wire.cpp @@ -15,6 +15,8 @@ You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + + Modified 2012 by Todd Krein (todd@krein.org) to implement repeated starts */ extern "C" { @@ -73,14 +75,14 @@ void TwoWire::begin(int address) begin((uint8_t)address); } -uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity) +uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity, uint8_t sendStop) { // clamp to buffer length if(quantity > BUFFER_LENGTH){ quantity = BUFFER_LENGTH; } // perform blocking read into buffer - uint8_t read = twi_readFrom(address, rxBuffer, quantity); + uint8_t read = twi_readFrom(address, rxBuffer, quantity, sendStop); // set rx buffer iterator vars rxBufferIndex = 0; rxBufferLength = read; @@ -88,9 +90,19 @@ uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity) return read; } +uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity) +{ + return requestFrom((uint8_t)address, (uint8_t)quantity, (uint8_t)true); +} + uint8_t TwoWire::requestFrom(int address, int quantity) { - return requestFrom((uint8_t)address, (uint8_t)quantity); + return requestFrom((uint8_t)address, (uint8_t)quantity, (uint8_t)true); +} + +uint8_t TwoWire::requestFrom(int address, int quantity, int sendStop) +{ + return requestFrom((uint8_t)address, (uint8_t)quantity, (uint8_t)sendStop); } void TwoWire::beginTransmission(uint8_t address) @@ -109,10 +121,23 @@ void TwoWire::beginTransmission(int address) beginTransmission((uint8_t)address); } -uint8_t TwoWire::endTransmission(void) +// +// Originally, 'endTransmission' was an f(void) function. +// It has been modified to take one parameter indicating +// whether or not a STOP should be performed on the bus. +// Calling endTransmission(false) allows a sketch to +// perform a repeated start. +// +// WARNING: Nothing in the library keeps track of whether +// the bus tenure has been properly ended with a STOP. It +// is very possible to leave the bus in a hung state if +// no call to endTransmission(true) is made. Some I2C +// devices will behave oddly if they do not see a STOP. +// +uint8_t TwoWire::endTransmission(uint8_t sendStop) { // transmit buffer (blocking) - int8_t ret = twi_writeTo(txAddress, txBuffer, txBufferLength, 1); + int8_t ret = twi_writeTo(txAddress, txBuffer, txBufferLength, 1, sendStop); // reset tx buffer iterator vars txBufferIndex = 0; txBufferLength = 0; @@ -121,6 +146,14 @@ uint8_t TwoWire::endTransmission(void) return ret; } +// This provides backwards compatibility with the original +// definition, and expected behaviour, of endTransmission +// +uint8_t TwoWire::endTransmission(void) +{ + return endTransmission(true); +} + // must be called in: // slave tx event callback // or after beginTransmission(address) diff --git a/libraries/Wire/Wire.h b/libraries/Wire/Wire.h index 9ea4afd..a93d0f5 100755 --- a/libraries/Wire/Wire.h +++ b/libraries/Wire/Wire.h @@ -15,6 +15,8 @@ You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + + Modified 2012 by Todd Krein (todd@krein.org) to implement repeated starts */ #ifndef TwoWire_h @@ -50,8 +52,11 @@ class TwoWire : public Stream void beginTransmission(uint8_t); void beginTransmission(int); uint8_t endTransmission(void); + uint8_t endTransmission(uint8_t); uint8_t requestFrom(uint8_t, uint8_t); + uint8_t requestFrom(uint8_t, uint8_t, uint8_t); uint8_t requestFrom(int, int); + uint8_t requestFrom(int, int, int); virtual size_t write(uint8_t); virtual size_t write(const uint8_t *, size_t); virtual int available(void); diff --git a/libraries/Wire/utility/twi.c b/libraries/Wire/utility/twi.c index d80114b..6b2db3c 100644 --- a/libraries/Wire/utility/twi.c +++ b/libraries/Wire/utility/twi.c @@ -15,6 +15,8 @@ You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + + Modified 2012 by Todd Krein (todd@krein.org) to implement repeated starts */ #include <math.h> @@ -37,14 +39,16 @@ #include "twi.h" static volatile uint8_t twi_state; -static uint8_t twi_slarw; +static volatile uint8_t twi_slarw; +static volatile uint8_t twi_sendStop; // should the transaction end with a stop +static volatile uint8_t twi_inRepStart; // in the middle of a repeated start static void (*twi_onSlaveTransmit)(void); static void (*twi_onSlaveReceive)(uint8_t*, int); static uint8_t twi_masterBuffer[TWI_BUFFER_LENGTH]; static volatile uint8_t twi_masterBufferIndex; -static uint8_t twi_masterBufferLength; +static volatile uint8_t twi_masterBufferLength; static uint8_t twi_txBuffer[TWI_BUFFER_LENGTH]; static volatile uint8_t twi_txBufferIndex; @@ -65,6 +69,8 @@ void twi_init(void) { // initialize state twi_state = TWI_READY; + twi_sendStop = true; // default value + twi_inRepStart = false; // activate internal pullups for twi. digitalWrite(SDA, 1); @@ -103,9 +109,10 @@ void twi_setAddress(uint8_t address) * Input address: 7bit i2c device address * data: pointer to byte array * length: number of bytes to read into array + * sendStop: Boolean indicating whether to send a stop at the end * Output number of bytes read */ -uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length) +uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sendStop) { uint8_t i; @@ -119,6 +126,7 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length) continue; } twi_state = TWI_MRX; + twi_sendStop = sendStop; // reset error state (0xFF.. no error occured) twi_error = 0xFF; @@ -135,8 +143,20 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length) twi_slarw = TW_READ; twi_slarw |= address << 1; - // send start condition - TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA); + if (true == twi_inRepStart) { + // if we're in the repeated start state, then we've already sent the start, + // (@@@ we hope), and the TWI statemachine is just waiting for the address byte. + // We need to remove ourselves from the repeated start state before we enable interrupts, + // since the ISR is ASYNC, and we could get confused if we hit the ISR before cleaning + // up. Also, don't enable the START interrupt. There may be one pending from the + // repeated start that we sent outselves, and that would really confuse things. + twi_inRepStart = false; // remember, we're dealing with an ASYNC ISR + TWDR = twi_slarw; + TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE); // enable INTs, but not START + } + else + // send start condition + TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA); // wait for read operation to complete while(TWI_MRX == twi_state){ @@ -162,13 +182,14 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length) * data: pointer to byte array * length: number of bytes in array * wait: boolean indicating to wait for write or not + * sendStop: boolean indicating whether or not to send a stop at the end * Output 0 .. success * 1 .. length to long for buffer * 2 .. address send, NACK received * 3 .. data send, NACK received * 4 .. other twi error (lost bus arbitration, bus error, ..) */ -uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait) +uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait, uint8_t sendStop) { uint8_t i; @@ -182,6 +203,7 @@ uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait continue; } twi_state = TWI_MTX; + twi_sendStop = sendStop; // reset error state (0xFF.. no error occured) twi_error = 0xFF; @@ -198,8 +220,23 @@ uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait twi_slarw = TW_WRITE; twi_slarw |= address << 1; - // send start condition - TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA); + // if we're in a repeated start, then we've already sent the START + // in the ISR. Don't do it again. + // + if (true == twi_inRepStart) { + // if we're in the repeated start state, then we've already sent the start, + // (@@@ we hope), and the TWI statemachine is just waiting for the address byte. + // We need to remove ourselves from the repeated start state before we enable interrupts, + // since the ISR is ASYNC, and we could get confused if we hit the ISR before cleaning + // up. Also, don't enable the START interrupt. There may be one pending from the + // repeated start that we sent outselves, and that would really confuse things. + twi_inRepStart = false; // remember, we're dealing with an ASYNC ISR + TWDR = twi_slarw; + TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE); // enable INTs, but not START + } + else + // send start condition + TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE) | _BV(TWSTA); // enable INTs // wait for write operation to complete while(wait && (TWI_MTX == twi_state)){ @@ -343,7 +380,16 @@ SIGNAL(TWI_vect) TWDR = twi_masterBuffer[twi_masterBufferIndex++]; twi_reply(1); }else{ - twi_stop(); + if (twi_sendStop) + twi_stop(); + else { + twi_inRepStart = true; // we're gonna send the START + // don't enable the interrupt. We'll generate the start, but we + // avoid handling the interrupt until we're in the next transaction, + // at the point where we would normally issue the start. + TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ; + twi_state = TWI_READY; + } } break; case TW_MT_SLA_NACK: // address sent, nack received @@ -374,6 +420,17 @@ SIGNAL(TWI_vect) case TW_MR_DATA_NACK: // data received, nack sent // put final byte into buffer twi_masterBuffer[twi_masterBufferIndex++] = TWDR; + if (twi_sendStop) + twi_stop(); + else { + twi_inRepStart = true; // we're gonna send the START + // don't enable the interrupt. We'll generate the start, but we + // avoid handling the interrupt until we're in the next transaction, + // at the point where we would normally issue the start. + TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ; + twi_state = TWI_READY; + } + break; case TW_MR_SLA_NACK: // address sent, nack received twi_stop(); break; diff --git a/libraries/Wire/utility/twi.h b/libraries/Wire/utility/twi.h index 831b928..6526593 100755 --- a/libraries/Wire/utility/twi.h +++ b/libraries/Wire/utility/twi.h @@ -40,8 +40,8 @@ void twi_init(void); void twi_setAddress(uint8_t); - uint8_t twi_readFrom(uint8_t, uint8_t*, uint8_t); - uint8_t twi_writeTo(uint8_t, uint8_t*, uint8_t, uint8_t); + uint8_t twi_readFrom(uint8_t, uint8_t*, uint8_t, uint8_t); + uint8_t twi_writeTo(uint8_t, uint8_t*, uint8_t, uint8_t, uint8_t); uint8_t twi_transmit(const uint8_t*, uint8_t); void twi_attachSlaveRxEvent( void (*)(uint8_t*, int) ); void twi_attachSlaveTxEvent( void (*)(void) ); |