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add support for I2C repeated start, tested with MB85RC256V #78

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add support for I2C repeated start, tested with MB85RC256V #78

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12 changes: 7 additions & 5 deletions cores/arduino/SERCOM.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -485,17 +485,19 @@ void SERCOM::prepareCommandBitsWire(uint8_t cmd)
}
}

bool SERCOM::startTransmissionWIRE(uint8_t address, SercomWireReadWriteFlag flag)
bool SERCOM::startTransmissionWIRE(uint8_t address, SercomWireReadWriteFlag flag, bool _repeatstart)
{
// 7-bits address + 1-bits R/W
address = (address << 0x1ul) | flag;

// Wait idle bus mode
while ( !isBusIdleWIRE() );
// Wait idle bus mode (except repeated start)
if (! _repeatstart) {
while ( !isBusIdleWIRE() );
}

// Send start and address
// Send start and address, in repeated start mode this will kick off the repstart too!
sercom->I2CM.ADDR.bit.ADDR = address;

// Address Transmitted
if ( flag == WIRE_WRITE_FLAG ) // Write mode
{
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2 changes: 1 addition & 1 deletion cores/arduino/SERCOM.h
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Expand Up @@ -193,7 +193,7 @@ class SERCOM
void prepareNackBitWIRE( void ) ;
void prepareAckBitWIRE( void ) ;
void prepareCommandBitsWire(uint8_t cmd);
bool startTransmissionWIRE(uint8_t address, SercomWireReadWriteFlag flag) ;
bool startTransmissionWIRE(uint8_t address, SercomWireReadWriteFlag flag, bool rs = false);
bool sendDataMasterWIRE(uint8_t data) ;
bool sendDataSlaveWIRE(uint8_t data) ;
bool isMasterWIRE( void ) ;
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17 changes: 15 additions & 2 deletions libraries/Wire/Wire.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@ TwoWire::TwoWire(SERCOM * s, uint8_t pinSDA, uint8_t pinSCL)
this->_uc_pinSDA=pinSDA;
this->_uc_pinSCL=pinSCL;
transmissionBegun = false;
_repeatedstart = false;
}

void TwoWire::begin(void) {
Expand Down Expand Up @@ -71,7 +72,7 @@ uint8_t TwoWire::requestFrom(uint8_t address, size_t quantity, bool stopBit)

size_t byteRead = 0;

if(sercom->startTransmissionWIRE(address, WIRE_READ_FLAG))
if(sercom->startTransmissionWIRE(address, WIRE_READ_FLAG, _repeatedstart))
{
// Read first data
rxBuffer.store_char(sercom->readDataWIRE());
Expand Down Expand Up @@ -114,6 +115,13 @@ uint8_t TwoWire::endTransmission(bool stopBit)
{
transmissionBegun = false ;

SercomMasterCommandWire cmd;
if (stopBit) {
_repeatedstart = false;
} else {
_repeatedstart = true;
}

// Start I2C transmission
if ( !sercom->startTransmissionWIRE( txAddress, WIRE_WRITE_FLAG ) )
{
Expand All @@ -131,7 +139,12 @@ uint8_t TwoWire::endTransmission(bool stopBit)
return 3 ; // Nack or error
}
}
sercom->prepareCommandBitsWire(WIRE_MASTER_ACT_STOP);

if (stopBit) {
sercom->prepareCommandBitsWire(WIRE_MASTER_ACT_STOP);
}
/* We dont actually send any command now, next time we try to do a read
it will automagically send a repeated start, see Table 27-12. Command Description */

return 0;
}
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4 changes: 3 additions & 1 deletion libraries/Wire/Wire.h
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Expand Up @@ -60,14 +60,16 @@ class TwoWire : public Stream
using Print::write;

void onService(void);

private:
SERCOM * sercom;

uint8_t _uc_pinSDA;
uint8_t _uc_pinSCL;

bool transmissionBegun;

bool _repeatedstart;

// RX Buffer
RingBuffer rxBuffer;

Expand Down