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 #include #include -// -// 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 // // 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 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);