diff options
Diffstat (limited to 'libraries/SoftwareSerial')
| -rw-r--r-- | libraries/SoftwareSerial/SoftwareSerial.cpp | 186 | ||||
| -rw-r--r-- | libraries/SoftwareSerial/SoftwareSerial.h | 4 |
2 files changed, 69 insertions, 121 deletions
diff --git a/libraries/SoftwareSerial/SoftwareSerial.cpp b/libraries/SoftwareSerial/SoftwareSerial.cpp index d1d2008..2977b1c 100644 --- a/libraries/SoftwareSerial/SoftwareSerial.cpp +++ b/libraries/SoftwareSerial/SoftwareSerial.cpp @@ -42,92 +42,7 @@ http://arduiniana.org. #include <avr/pgmspace.h>
#include <Arduino.h>
#include <SoftwareSerial.h>
-//
-// Lookup table
-//
-typedef struct _DELAY_TABLE
-{
- long baud;
- unsigned short rx_delay_centering;
- unsigned short rx_delay_intrabit;
- unsigned short rx_delay_stopbit;
- unsigned short tx_delay;
-} DELAY_TABLE;
-
-#if F_CPU == 16000000
-
-static const DELAY_TABLE PROGMEM table[] =
-{
- // baud rxcenter rxintra rxstop tx
- { 115200, 1, 17, 17, 12, },
- { 57600, 10, 37, 37, 33, },
- { 38400, 25, 57, 57, 54, },
- { 31250, 31, 70, 70, 68, },
- { 28800, 34, 77, 77, 74, },
- { 19200, 54, 117, 117, 114, },
- { 14400, 74, 156, 156, 153, },
- { 9600, 114, 236, 236, 233, },
- { 4800, 233, 474, 474, 471, },
- { 2400, 471, 950, 950, 947, },
- { 1200, 947, 1902, 1902, 1899, },
- { 600, 1902, 3804, 3804, 3800, },
- { 300, 3804, 7617, 7617, 7614, },
-};
-
-const int XMIT_START_ADJUSTMENT = 5;
-
-#elif F_CPU == 8000000
-
-static const DELAY_TABLE table[] PROGMEM =
-{
- // baud rxcenter rxintra rxstop tx
- { 115200, 1, 5, 5, 3, },
- { 57600, 1, 15, 15, 13, },
- { 38400, 2, 25, 26, 23, },
- { 31250, 7, 32, 33, 29, },
- { 28800, 11, 35, 35, 32, },
- { 19200, 20, 55, 55, 52, },
- { 14400, 30, 75, 75, 72, },
- { 9600, 50, 114, 114, 112, },
- { 4800, 110, 233, 233, 230, },
- { 2400, 229, 472, 472, 469, },
- { 1200, 467, 948, 948, 945, },
- { 600, 948, 1895, 1895, 1890, },
- { 300, 1895, 3805, 3805, 3802, },
-};
-
-const int XMIT_START_ADJUSTMENT = 4;
-
-#elif F_CPU == 20000000
-
-// 20MHz support courtesy of the good people at macegr.com.
-// Thanks, Garrett!
-
-static const DELAY_TABLE PROGMEM table[] =
-{
- // baud rxcenter rxintra rxstop tx
- { 115200, 3, 21, 21, 18, },
- { 57600, 20, 43, 43, 41, },
- { 38400, 37, 73, 73, 70, },
- { 31250, 45, 89, 89, 88, },
- { 28800, 46, 98, 98, 95, },
- { 19200, 71, 148, 148, 145, },
- { 14400, 96, 197, 197, 194, },
- { 9600, 146, 297, 297, 294, },
- { 4800, 296, 595, 595, 592, },
- { 2400, 592, 1189, 1189, 1186, },
- { 1200, 1187, 2379, 2379, 2376, },
- { 600, 2379, 4759, 4759, 4755, },
- { 300, 4759, 9523, 9523, 9520, },
-};
-
-const int XMIT_START_ADJUSTMENT = 6;
-
-#else
-
-#error This version of SoftwareSerial supports only 20, 16 and 8MHz processors
-
-#endif
+#include <util/delay_basic.h>
//
// Statics
@@ -162,16 +77,7 @@ inline void DebugPulse(uint8_t pin, uint8_t count) /* static */
inline void SoftwareSerial::tunedDelay(uint16_t delay) {
- uint8_t tmp=0;
-
- asm volatile("sbiw %0, 0x01 \n\t"
- "ldi %1, 0xFF \n\t"
- "cpi %A0, 0xFF \n\t"
- "cpc %B0, %1 \n\t"
- "brne .-10 \n\t"
- : "+r" (delay), "+a" (tmp)
- : "0" (delay)
- );
+ _delay_loop_2(delay);
}
// This function sets the current object as the "listening"
@@ -256,12 +162,6 @@ void SoftwareSerial::recv() d |= 0x80;
}
- // skip the stop bit
- tunedDelay(_rx_delay_stopbit);
- DebugPulse(_DEBUG_PIN2, 1);
-
- // Re-enable interrupts when we're sure to be inside the stop bit
- setRxIntMsk(true);
if (_inverse_logic)
d = ~d;
@@ -280,6 +180,14 @@ void SoftwareSerial::recv() #endif
_buffer_overflow = true;
}
+
+ // skip the stop bit
+ tunedDelay(_rx_delay_stopbit);
+ DebugPulse(_DEBUG_PIN1, 1);
+
+ // Re-enable interrupts when we're sure to be inside the stop bit
+ setRxIntMsk(true);
+
}
#if GCC_VERSION < 40302
@@ -378,6 +286,13 @@ void SoftwareSerial::setRX(uint8_t rx) _receivePortRegister = portInputRegister(port);
}
+uint16_t SoftwareSerial::subtract_cap(uint16_t num, uint16_t sub) {
+ if (num > sub)
+ return num - sub;
+ else
+ return 1;
+}
+
//
// Public methods
//
@@ -386,26 +301,55 @@ void SoftwareSerial::begin(long speed) {
_rx_delay_centering = _rx_delay_intrabit = _rx_delay_stopbit = _tx_delay = 0;
- for (unsigned i=0; i<sizeof(table)/sizeof(table[0]); ++i)
- {
- long baud = pgm_read_dword(&table[i].baud);
- if (baud == speed)
- {
- if (digitalPinToPCICR(_receivePin))
- {
- // Only setup rx when we have a valid PCINT for this pin
- _rx_delay_centering = pgm_read_word(&table[i].rx_delay_centering);
- _rx_delay_intrabit = pgm_read_word(&table[i].rx_delay_intrabit);
- _rx_delay_stopbit = pgm_read_word(&table[i].rx_delay_stopbit);
- }
- _tx_delay = pgm_read_word(&table[i].tx_delay);
- break;
- }
- }
+ // Precalculate the various delays, in number of 4-cycle delays
+ uint16_t bit_delay = (F_CPU / speed) / 4;
+
+ // 12 (gcc 4.8.2) or 13 (gcc 4.3.2) cycles from start bit to first bit,
+ // 15 (gcc 4.8.2) or 16 (gcc 4.3.2) cycles between bits,
+ // 12 (gcc 4.8.2) or 14 (gcc 4.3.2) cycles from last bit to stop bit
+ // These are all close enough to just use 15 cycles, since the inter-bit
+ // timings are the most critical (deviations stack 8 times)
+ _tx_delay = subtract_cap(bit_delay, 15 / 4);
+
+ // Only setup rx when we have a valid PCINT for this pin
+ if (digitalPinToPCICR(_receivePin)) {
+ #if GCC_VERSION > 40800
+ // Timings counted from gcc 4.8.2 output. This works up to 115200 on
+ // 16Mhz and 57600 on 8Mhz.
+ //
+ // When the start bit occurs, there are 3 or 4 cycles before the
+ // interrupt flag is set, 4 cycles before the PC is set to the right
+ // interrupt vector address and the old PC is pushed on the stack,
+ // and then 75 cycles of instructions (including the RJMP in the
+ // ISR vector table) until the first delay. After the delay, there
+ // are 17 more cycles until the pin value is read (excluding the
+ // delay in the loop).
+ // We want to have a total delay of 1.5 bit time. Inside the loop,
+ // we already wait for 1 bit time - 23 cycles, so here we wait for
+ // 0.5 bit time - (71 + 18 - 22) cycles.
+ _rx_delay_centering = subtract_cap(bit_delay / 2, (4 + 4 + 75 + 17 - 23) / 4);
+
+ // There are 23 cycles in each loop iteration (excluding the delay)
+ _rx_delay_intrabit = subtract_cap(bit_delay, 23 / 4);
+
+ // There are 37 cycles from the last bit read to the start of
+ // stopbit delay and 11 cycles from the delay until the interrupt
+ // mask is enabled again (which _must_ happen during the stopbit).
+ // This delay aims at 3/4 of a bit time, meaning the end of the
+ // delay will be at 1/4th of the stopbit. This allows some extra
+ // time for ISR cleanup, which makes 115200 baud at 16Mhz work more
+ // reliably
+ _rx_delay_stopbit = subtract_cap(bit_delay * 3 / 4, (37 + 11) / 4);
+ #else // Timings counted from gcc 4.3.2 output
+ // Note that this code is a _lot_ slower, mostly due to bad register
+ // allocation choices of gcc. This works up to 57600 on 16Mhz and
+ // 38400 on 8Mhz.
+ _rx_delay_centering = subtract_cap(bit_delay / 2, (4 + 4 + 97 + 29 - 11) / 4);
+ _rx_delay_intrabit = subtract_cap(bit_delay, 11 / 4);
+ _rx_delay_stopbit = subtract_cap(bit_delay * 3 / 4, (44 + 17) / 4);
+ #endif
+
- // Set up RX interrupts, but only if we have a valid RX baud rate
- if (_rx_delay_stopbit)
- {
// Enable the PCINT for the entire port here, but never disable it
// (others might also need it, so we disable the interrupt by using
// the per-pin PCMSK register).
diff --git a/libraries/SoftwareSerial/SoftwareSerial.h b/libraries/SoftwareSerial/SoftwareSerial.h index 2b12598..e28da98 100644 --- a/libraries/SoftwareSerial/SoftwareSerial.h +++ b/libraries/SoftwareSerial/SoftwareSerial.h @@ -56,6 +56,7 @@ private: volatile uint8_t *_pcint_maskreg;
uint8_t _pcint_maskvalue;
+ // Expressed as 4-cycle delays (must never be 0!)
uint16_t _rx_delay_centering;
uint16_t _rx_delay_intrabit;
uint16_t _rx_delay_stopbit;
@@ -78,6 +79,9 @@ private: void setRX(uint8_t receivePin);
void setRxIntMsk(bool enable) __attribute__((__always_inline__));
+ // Return num - sub, or 1 if the result would be < 1
+ static uint16_t subtract_cap(uint16_t num, uint16_t sub);
+
// private static method for timing
static inline void tunedDelay(uint16_t delay);
|