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Added peek and unsetting prescalers at ignore #26

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Added peek and unsetting prescalers at ignore #26

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19a4266
Added peak and unsetting prescalers at ignore
SRGDamia1 May 18, 2018
c0b9bd0
Fixed head/tail in peek, cleaned comments
SRGDamia1 May 21, 2018
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8 changes: 8 additions & 0 deletions .gitignore
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Original file line number Diff line number Diff line change
Expand Up @@ -41,3 +41,11 @@ $RECYCLE.BIN/
Network Trash Folder
Temporary Items
.apdisk

# Atom / PlatformIO
.pioenvs
.piolibdeps
.clang_complete
.gcc-flags.json
lib/readme.txt
platformio.ini
168 changes: 114 additions & 54 deletions src/NeoSWSerial.cpp
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Expand Up @@ -42,19 +42,27 @@ static const uint8_t BITS_PER_TICK_31250_Q10 = 128;
static const uint8_t BITS_PER_TICK_38400_Q10 = 157;
// 1s/(38400 bits) * (1 tick)/(4 us) * 2^10 "multiplier"

// Choose the timer to use
#if F_CPU == 16000000L
#define TCNTX TCNT0
#define TCNTX TCNT0 // 8-bit timer w/ PWM, default prescaler has divisor of 64, thus 250kHz
#define PCI_FLAG_REGISTER PCIFR

#elif F_CPU == 8000000L
#if defined(__AVR_ATtiny25__) | \
defined(__AVR_ATtiny45__) | \
defined(__AVR_ATtiny85__)
#define TCNTX TCNT1
defined(__AVR_ATtiny85__)
#define TCNTX TCNT1 // 8-bit timer/counter w/ independent prescaler
#define PCI_FLAG_REGISTER GIFR
static uint8_t preNSWS_TCCR1;

#else
#define TCNTX TCNT2
// Have to use timer 2 for an 8 MHz system because timer 0 doesn't have the correct prescaler
#define TCNTX TCNT2 // 8-bit timer w/ PWM, asynchronous operation, and independent prescaler
#define PCI_FLAG_REGISTER PCIFR
static uint8_t preNSWS_TCCR2A;
static uint8_t preNSWS_TCCR2B;
#endif

#endif

static NeoSWSerial *listener = (NeoSWSerial *) NULL;
Expand Down Expand Up @@ -145,15 +153,21 @@ void NeoSWSerial::listen()
*txPort |= txBitMask; // high = idle
pinMode(txPin, OUTPUT);

// Set the timer prescaling as necessary - want to be running at 250kHz
if (F_CPU == 8000000L) {
// Have to use timer 2 for an 8 MHz system.
#if defined(__AVR_ATtiny25__) | \
defined(__AVR_ATtiny45__) | \
defined(__AVR_ATtiny85__)
TCCR1 = 0x06; // divide by 32
defined(__AVR_ATtiny85__)
preNSWS_TCCR1 = TCCR1;
TCCR1 = 0x06; // 0b00000110 - Clock Select bits 12 & 11 on - prescaling source = CK/32
// timer now running at 8MHz/32 = 250kHz
#else
TCCR2A = 0x00;
TCCR2B = 0x03; // divide by 32
preNSWS_TCCR2A = TCCR2A;
preNSWS_TCCR2B = TCCR2B;
TCCR2A = 0x00; // "normal" operation - Normal port operation, OC2A & OC2B disconnected
TCCR2B = 0x03; // 0b00000011 - Clock Select bits 21 & 20 on - prescaler set to clkT2S/32
// timer now running at 8MHz/32 = 250kHz
#endif
}

Expand All @@ -164,32 +178,32 @@ void NeoSWSerial::listen()
flush();

// Set up timings based on baud rate

switch (_baudRate) {
case 9600:
txBitWidth = TICKS_PER_BIT_9600 ;
bitsPerTick_Q10 = BITS_PER_TICK_38400_Q10 >> 2;
rxWindowWidth = 10;
break;
case 31250:
if (F_CPU > 12000000L) {
txBitWidth = TICKS_PER_BIT_31250;
bitsPerTick_Q10 = BITS_PER_TICK_31250_Q10;
rxWindowWidth = 5;
break;
} // else use 19200
case 38400:
if (F_CPU > 12000000L) {
txBitWidth = TICKS_PER_BIT_9600 >> 2;
bitsPerTick_Q10 = BITS_PER_TICK_38400_Q10 ;
rxWindowWidth = 4;
break;
} // else use 19200
}
case 31250:
if (F_CPU > 12000000L) {
txBitWidth = TICKS_PER_BIT_31250;
bitsPerTick_Q10 = BITS_PER_TICK_31250_Q10;
rxWindowWidth = 5;
break;
}
case 19200:
txBitWidth = TICKS_PER_BIT_9600 >> 1;
bitsPerTick_Q10 = BITS_PER_TICK_38400_Q10 >> 1;
rxWindowWidth = 6;
break;
case 9600: // default is 9600
txBitWidth = TICKS_PER_BIT_9600 ;
bitsPerTick_Q10 = BITS_PER_TICK_38400_Q10 >> 2;
rxWindowWidth = 10;
break;
}

// Enable the pin change interrupts
Expand Down Expand Up @@ -225,6 +239,18 @@ void NeoSWSerial::ignore()
SREG = prevSREG;
}

if (F_CPU == 8000000L) {
// Un-set the timer pre-scalers
#if defined(__AVR_ATtiny25__) | \
defined(__AVR_ATtiny45__) | \
defined(__AVR_ATtiny85__)
TCCR1 = preNSWS_TCCR1;
#else
TCCR2A = preNSWS_TCCR2A;
TCCR2B = preNSWS_TCCR2B;
#endif
}

} // ignore

//----------------------------------------------------------------------------
Expand Down Expand Up @@ -252,7 +278,7 @@ 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 All @@ -268,6 +294,14 @@ int NeoSWSerial::available()

//----------------------------------------------------------------------------

int NeoSWSerial::peek()
{
if (rxHead == rxTail) return -1;
return rxBuffer[rxTail];
} // peek

//----------------------------------------------------------------------------

int NeoSWSerial::read()
{
if (rxHead == rxTail) return -1;
Expand Down Expand Up @@ -305,62 +339,88 @@ void NeoSWSerial::startChar()

void NeoSWSerial::rxISR( uint8_t rxPort )
{
uint8_t t0 = TCNTX; // time of data transition (plus ISR latency)
uint8_t d = rxPort & rxBitMask; // read RX data level
uint8_t t0 = TCNTX; // time of data transition (plus ISR latency)
uint8_t d = rxPort & rxBitMask; // read RX data level

// Check if we're ready for a start bit, and if this could possibly be it
// Otherwise, just ignore the interrupt and exit
if (rxState == WAITING_FOR_START_BIT) {

// If it looks like a start bit then initialize;
// otherwise ignore the rising edge and exit.

if (d != 0) return; // it's high so not a start bit, exit
// If it is HIGH it's not a start bit, exit
if (d != 0) return;
// If it is LOW, this should be a start bit
// Thus set the rxStat to 0, create an empty character, and a new mask with a 1 in the lowest place
startChar();

} else { // data bit or stop bit (probably) received
}

// if the character is incomplete, and this is not a start bit,
// then this change is from a data or stop bit
else {

DBG_NSS_ARRAY(bitTransitionTimes, bitTransitions, (t0-prev_t0));

// Determine how many bit periods have elapsed since the last transition.

// check how many bit times have passed since the last change
// the rxWindowWidth is just a fudge factor
uint16_t rxBits = bitTimes( t0-prev_t0 );
uint8_t bitsLeft = 9 - rxState; // ignores stop bit
// calculate how many *data* bits should be left
// We know the start bit is past and are ignoring the stop bit
uint8_t bitsLeft = 9 - rxState;
// note that a new character *may* have started if more bits have been
// received than should be left.
// This will also happen if last bit(s) of the character are all 0's.
bool nextCharStarted = (rxBits > bitsLeft);

if (nextCharStarted)
DBG_NSS_ARRAY(rxStartCompletionBits,rxStartCompletions,(10*rxBits + bitsLeft));

uint8_t bitsThisFrame = nextCharStarted ? bitsLeft : rxBits;

// check how many data bits have been sent in this frame
// If the total number of bits in this frame is more than the number of data
// bits remaining in the character, then the number of data bits is equal
// to the number of bits remaining for the character and partiy. If the total
// number of bits in this frame is less than the number of data bits left
// for the character and parity, then the number of data bits received
// in this frame is equal to the total number of bits received in this frame.
// translation:
// if nextCharStarted then bitsThisFrame = bitsLeft
// else bitsThisFrame = rxBits
uint8_t bitsThisFrame = nextCharStarted ? bitsLeft : rxBits;
// Tick up the rxState by that many bits
rxState += bitsThisFrame;

// Set all those bits

// Set all the bits received between the last change and this change
// If the current state is LOW (and it just became so), then all bits between
// the last change and now must have been HIGH.
if (d == 0) {
// back fill previous bits with 1's
while (bitsThisFrame-- > 0) {
rxValue |= rxMask;
rxMask = rxMask << 1;
rxValue |= rxMask; // Add a 1 to the LSB/right-most place
rxMask = rxMask << 1;; // Shift the 1 in the mask up by one position
}
rxMask = rxMask << 1;
} else { // d==1
rxMask = rxMask << 1; // Shift the 1 in the mask up by one more position
}
// If the current state is HIGH (and it just became so), then this bit is HIGH
// but all bits between the last change and now must have been LOW
else { // d==1
// previous bits were 0's so only this bit is a 1.
rxMask = rxMask << (bitsThisFrame-1);
rxValue |= rxMask;
rxMask = rxMask << (bitsThisFrame-1); // Shift the 1 in the mask up by the number of bits past
rxValue |= rxMask; // Add that shifted one to the character being created
}

// If 8th bit or stop bit then the character is complete.

if (rxState > 7) {
rxChar( rxValue );

// if this is HIGH, or we haven't exceeded the number of bits in a
// character (but have gotten all the data bits) then this should be a
// stop bit and we can start looking for a new start bit.
if ((d == 1) || !nextCharStarted) {
rxState = WAITING_FOR_START_BIT;
// DISABLE STOP BIT TIMER

rxState = WAITING_FOR_START_BIT; // DISABLE STOP BIT TIMER
} else {
// The last char ended with 1's, so this 0 is actually
// the start bit of the next character.

// If we just switched to LOW, or we've exceeded the total number of
// bits in a character, then the character must have ended with 1's/HIGH,
// and this new 0/LOW is actually the start bit of the next character.
startChar();
}
}
Expand Down Expand Up @@ -457,13 +517,13 @@ void NeoSWSerial::rxChar( uint8_t c )

#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 @@ -535,9 +595,9 @@ size_t NeoSWSerial::write(uint8_t txChar)

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
Expand All @@ -551,7 +611,7 @@ 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 Down
14 changes: 7 additions & 7 deletions src/NeoSWSerial.h
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Expand Up @@ -24,8 +24,8 @@
// This software serial library is intended as a more-efficient replacement
// for SoftwareSerial at baud rates 9600, 19200 and 38400.
//
// 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 @@ -42,9 +42,9 @@
// 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,...).
//
// v1.0 Nov 2014 jboyton - Created
Expand Down Expand Up @@ -75,12 +75,12 @@ class NeoSWSerial : public Stream
void begin(uint16_t baudRate=9600); // initialize, set baudrate, listen
void listen(); // enable RX interrupts
void ignore(); // disable RX interrupts
void setBaudRate(uint16_t baudRate); // 9600 [default], 19200, 38400
void setBaudRate(uint16_t baudRate); // 9600 [default], 19200, 31250, 38400
virtual int available();
virtual int read();
virtual size_t write(uint8_t txChar);
using Stream::write; // make the base class overloads visible
virtual int peek() { return 0; };
virtual int peek();
virtual void flush() {};
void end() { ignore(); }

Expand Down