diff options
| -rw-r--r-- | libraries/SoftwareSerial/SoftwareSerial.cpp | 48 |
1 files changed, 29 insertions, 19 deletions
diff --git a/libraries/SoftwareSerial/SoftwareSerial.cpp b/libraries/SoftwareSerial/SoftwareSerial.cpp index da9af30..621a2af 100644 --- a/libraries/SoftwareSerial/SoftwareSerial.cpp +++ b/libraries/SoftwareSerial/SoftwareSerial.cpp @@ -292,14 +292,6 @@ void SoftwareSerial::recv() #endif
}
-void SoftwareSerial::tx_pin_write(uint8_t pin_state)
-{
- if (pin_state == LOW)
- *_transmitPortRegister &= ~_transmitBitMask;
- else
- *_transmitPortRegister |= _transmitBitMask;
-}
-
uint8_t SoftwareSerial::rx_pin_read()
{
return *_receivePortRegister & _receiveBitMask;
@@ -477,29 +469,47 @@ size_t SoftwareSerial::write(uint8_t b) return 0;
}
+ // By declaring these as local variables, the compiler will put them
+ // in registers _before_ disabling interrupts and entering the
+ // critical timing sections below, which makes it a lot easier to
+ // verify the cycle timings
+ volatile uint8_t *reg = _transmitPortRegister;
+ uint8_t reg_mask = _transmitBitMask;
+ uint8_t inv_mask = ~_transmitBitMask;
uint8_t oldSREG = SREG;
+ bool inv = _inverse_logic;
+ uint16_t delay = _tx_delay;
+
+ if (inv)
+ b = ~b;
+
cli(); // turn off interrupts for a clean txmit
// Write the start bit
- tx_pin_write(_inverse_logic ? HIGH : LOW);
- tunedDelay(_tx_delay + XMIT_START_ADJUSTMENT);
+ if (inv)
+ *reg |= reg_mask;
+ else
+ *reg &= inv_mask;
- // Write each of the 8 bits
- if (_inverse_logic)
- b = ~b;
+ tunedDelay(delay);
- for (byte mask = 0x01; mask; mask <<= 1)
+ // Write each of the 8 bits
+ for (uint8_t i = 8; i > 0; --i)
{
- if (b & mask) // choose bit
- tx_pin_write(HIGH); // send 1
+ if (b & 1) // choose bit
+ *reg |= reg_mask; // send 1
else
- tx_pin_write(LOW); // send 0
+ *reg &= inv_mask; // send 0
- tunedDelay(_tx_delay);
+ tunedDelay(delay);
+ b >>= 1;
}
// restore pin to natural state
- tx_pin_write(_inverse_logic ? LOW : HIGH);
+ if (inv)
+ *reg &= inv_mask;
+ else
+ *reg |= reg_mask;
SREG = oldSREG; // turn interrupts back on
tunedDelay(_tx_delay);
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