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Half duplex support #4377

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19 changes: 16 additions & 3 deletions hardware/arduino/avr/libraries/SoftwareSerial/SoftwareSerial.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -246,13 +246,14 @@ ISR(PCINT3_vect, ISR_ALIASOF(PCINT0_vect));
//
// Constructor
//
SoftwareSerial::SoftwareSerial(uint8_t receivePin, uint8_t transmitPin, bool inverse_logic /* = false */) :
SoftwareSerial::SoftwareSerial(uint8_t receivePin, uint8_t transmitPin, bool inverse_logic /* = false */, bool full_duplex /* = true */) :
_rx_delay_centering(0),
_rx_delay_intrabit(0),
_rx_delay_stopbit(0),
_tx_delay(0),
_buffer_overflow(false),
_inverse_logic(inverse_logic)
_inverse_logic(inverse_logic),
_full_duplex(full_duplex)
{
setTX(transmitPin);
setRX(receivePin);
Expand All @@ -273,7 +274,11 @@ void SoftwareSerial::setTX(uint8_t tx)
// output hihg. Now, it is input with pullup for a short while, which
// is fine. With inverse logic, either order is fine.
digitalWrite(tx, _inverse_logic ? LOW : HIGH);
pinMode(tx, OUTPUT);
if(_full_duplex)
pinMode(tx, OUTPUT);
else
pinMode(tx, INPUT);
_transmitPin = tx;
_transmitBitMask = digitalPinToBitMask(tx);
uint8_t port = digitalPinToPort(tx);
_transmitPortRegister = portOutputRegister(port);
Expand Down Expand Up @@ -418,6 +423,9 @@ size_t SoftwareSerial::write(uint8_t b)
setWriteError();
return 0;
}

if(!_full_duplex)
pinMode(_transmitPin, OUTPUT);

// By declaring these as local variables, the compiler will put them
// in registers _before_ disabling interrupts and entering the
Expand Down Expand Up @@ -461,6 +469,11 @@ size_t SoftwareSerial::write(uint8_t b)
else
*reg |= reg_mask;

if(!_full_duplex){
pinMode(_transmitPin, INPUT);
*reg |= reg_mask; // send 1
}

SREG = oldSREG; // turn interrupts back on
tunedDelay(_tx_delay);

Expand Down
4 changes: 3 additions & 1 deletion hardware/arduino/avr/libraries/SoftwareSerial/SoftwareSerial.h
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,7 @@ class SoftwareSerial : public Stream
uint8_t _receivePin;
uint8_t _receiveBitMask;
volatile uint8_t *_receivePortRegister;
uint8_t _transmitPin;
uint8_t _transmitBitMask;
volatile uint8_t *_transmitPortRegister;
volatile uint8_t *_pcint_maskreg;
Expand All @@ -64,6 +65,7 @@ class SoftwareSerial : public Stream

uint16_t _buffer_overflow:1;
uint16_t _inverse_logic:1;
uint16_t _full_duplex:1;

// static data
static char _receive_buffer[_SS_MAX_RX_BUFF];
Expand All @@ -86,7 +88,7 @@ class SoftwareSerial : public Stream

public:
// public methods
SoftwareSerial(uint8_t receivePin, uint8_t transmitPin, bool inverse_logic = false);
SoftwareSerial(uint8_t receivePin, uint8_t transmitPin, bool inverse_logic = false, bool full_duplex = true);
~SoftwareSerial();
void begin(long speed);
bool listen();
Expand Down