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Add inverse_logic capability as per SoftwareSerial. #7

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Add inverse_logic capability as per SoftwareSerial. #7

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37 changes: 26 additions & 11 deletions NeoSWSerial.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,7 @@ static uint8_t rxTail; // buffer pointer output

static uint8_t rxBitMask, txBitMask; // port bit masks
static volatile uint8_t *txPort; // port register
static bool inv; //invert the signal on the line

//#define DEBUG_NEOSWSERIAL
#ifdef DEBUG_NEOSWSERIAL
Expand Down Expand Up @@ -115,8 +116,13 @@ void NeoSWSerial::listen()

txBitMask = digitalPinToBitMask( txPin );
txPort = portOutputRegister( digitalPinToPort( txPin ) );
inv = inverse;
// set idle state: logic 1
if (txPort)
*txPort |= txBitMask; // high = idle
if (inv)
*txPort &= ~txBitMask; // set TX line low
else
*txPort |= txBitMask; // set TX line high
pinMode(txPin, OUTPUT);

if (F_CPU == 8000000L) {
Expand All @@ -132,7 +138,7 @@ void NeoSWSerial::listen()
flush();

// Set up timings based on baud rate

switch (_baudRate) {
case 9600:
txBitWidth = TICKS_PER_BIT_9600 ;
Expand Down Expand Up @@ -212,7 +218,7 @@ void NeoSWSerial::setBaudRate(uint16_t baudRate)
int NeoSWSerial::available()
{
uint8_t avail = ((rxHead - rxTail + RX_BUFFER_SIZE) % RX_BUFFER_SIZE);

if (avail == 0) {
cli();
if (checkRxTime()) {
Expand Down Expand Up @@ -266,6 +272,9 @@ void NeoSWSerial::startChar()
void NeoSWSerial::rxISR( uint8_t rxPort )
{
uint8_t t0 = TCNTX; // time of data transition (plus ISR latency)
if (inv) {
rxPort = ~rxPort;
}
uint8_t d = rxPort & rxBitMask; // read RX data level

if (rxState == WAITING_FOR_START_BIT) {
Expand Down Expand Up @@ -337,6 +346,7 @@ bool NeoSWSerial::checkRxTime()
if (rxState != WAITING_FOR_START_BIT) {

uint8_t d = *rxPort & rxBitMask;
if (inv) d = ~d;

if (d) {
// Ended on a 1, see if it has been too long
Expand Down Expand Up @@ -410,13 +420,13 @@ ISR(PCINT0_vect)

#elif defined(__AVR_ATtiny25__) | \
defined(__AVR_ATtiny45__) | \
defined(__AVR_ATtiny85__)
defined(__AVR_ATtiny85__)

PCINT_ISR(0, PINB);

#elif defined(__AVR_ATtiny24__) | \
defined(__AVR_ATtiny44__) | \
defined(__AVR_ATtiny84__)
defined(__AVR_ATtiny84__)

PCINT_ISR(0, PINA);
PCINT_ISR(1, PINB);
Expand Down Expand Up @@ -471,21 +481,21 @@ size_t NeoSWSerial::write(uint8_t txChar)

uint8_t width; // ticks for one bit
uint8_t txBit = 0; // first bit is start bit
uint8_t b = 0; // start bit is low
bool b = false; // start bit is logic 0
uint8_t PCIbit = bit(digitalPinToPCICRbit(rxPin));

uint8_t prevSREG = SREG;
cli(); // send the character with interrupts disabled

uint8_t t0 = TCNTX; // start time

// TODO: This would benefit from an early break after
// TODO: This would benefit from an early break after
// the last 0 data bit. Then we could wait for the
// remaining 1 data bits and stop bit with interrupts
// remaining 1 data bits and stop bit with interrupts
// re-enabled.

while (txBit++ < 9) { // repeat for start bit + 8 data bits
if (b) // if bit is set
if (b != inv) // if desired state is high
*txPort |= txBitMask; // set TX line high
else
*txPort &= ~txBitMask; // else set TX line low
Expand All @@ -495,7 +505,7 @@ size_t NeoSWSerial::write(uint8_t txChar)
(width == TICKS_PER_BIT_9600/4) &&
(txBit & 0x01)) {
// The width is 6.5 ticks, so add a tick every other bit
width++;
width++;
}

// Hold the line for the bit duration
Expand All @@ -516,7 +526,12 @@ size_t NeoSWSerial::write(uint8_t txChar)
// Q: would a signed >> pull in a 1?
}

*txPort |= txBitMask; // stop bit is high
// stop bit is logic 1
if (inv)
*txPort &= ~txBitMask; // else set TX line low
else
*txPort |= txBitMask; // set TX line high

SREG = prevSREG; // interrupts on for stop bit
while ((uint8_t)(TCNTX - t0) < width) {
if (checkRxTime())
Expand Down
18 changes: 11 additions & 7 deletions NeoSWSerial.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,8 +13,8 @@
//
// Constructor: NeoSWSerial ss(RX_PIN, TX_PIN);
//
// Any of the pins supported by SoftwareSerial may be used. Pins (0-19)
// on the Uno may be used. Other boards can use any of the pins
// Any of the pins supported by SoftwareSerial may be used. Pins (0-19)
// on the Uno may be used. Other boards can use any of the pins
// allowed by digitalPinToPCMSK in pins_arduino.h
//
// This code uses a pin change interrupt on the selected RX pin.
Expand All @@ -25,9 +25,9 @@
// Supported baud rates are 9600 (default), 19200 and 38400.
// The baud rate is selectable at run time.
//
// The size of the RX buffer may be changed by editing the
// accompanying .cpp file. For optimal performance of the interrupt
// service routines, the buffer size should be chosen to be a
// The size of the RX buffer may be changed by editing the
// accompanying .cpp file. For optimal performance of the interrupt
// service routines, the buffer size should be chosen to be a
// power of 2 (i.e., 2, 4, 8, 16, 32, 64,...).
//
// Nov/Dec 2014 jboyton - Created
Expand All @@ -38,18 +38,20 @@
// Nov 2015 SlashDev - Add support for other boards,
// add end() and attach/detachInterrupt
// Jun 2016 SlashDev - Add support for all character values
//
// Jan 2017 Matthew Marks - Added support for inverse logic


class NeoSWSerial : public Stream
{
NeoSWSerial( const NeoSWSerial & ); // Not allowed
NeoSWSerial & operator =( const NeoSWSerial & ); // Not allowed

public:
NeoSWSerial(uint8_t receivePin, uint8_t transmitPin)
NeoSWSerial(uint8_t receivePin, uint8_t transmitPin, bool inverse_logic = false)
{
rxPin = receivePin;
txPin = transmitPin;
inverse = inverse_logic;
_isr = (isr_t) NULL;
}

Expand All @@ -70,6 +72,7 @@ class NeoSWSerial : public Stream

private:
uint8_t rxPin, txPin;
bool inverse;
volatile uint8_t *rxPort;

uint16_t _baudRate;
Expand All @@ -84,5 +87,6 @@ class NeoSWSerial : public Stream
public:
// visible only so the ISRs can call it...
static void rxISR( uint8_t port_input_register );
static bool invert; // invert levels on line
};
#endif