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- /*
- TinySoftwareSerial.cpp - Hardware serial library for Wiring
- Copyright (c) 2006 Nicholas Zambetti. All right reserved.
- This library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
- This library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
- You should have received a copy of the GNU Lesser General Public
- License along with this library; if not, write to the Free Software
- Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
- Modified 23 November 2006 by David A. Mellis
- Modified 28 September 2010 by Mark Sproul
- */
- #include <stdlib.h>
- #include <stdio.h>
- #include <string.h>
- #include <inttypes.h>
- #include "Arduino.h"
- #include "wiring_private.h"
- #if USE_SOFTWARE_SERIAL
- #include "TinySoftwareSerial.h"
- // Define constants and variables for buffering incoming serial data. We're
- // using a ring buffer (I think), in which rx_buffer_head is the index of the
- // location to which to write the next incoming character and rx_buffer_tail
- // is the index of the location from which to read.
- extern "C"{
- uint8_t getch() {
- uint8_t ch = 0;
- __asm__ __volatile__ (
- " rcall uartDelay\n" // Get to 0.25 of start bit (our baud is too fast, so give room to correct)
- "1: rcall uartDelay\n" // Wait 0.25 bit period
- " rcall uartDelay\n" // Wait 0.25 bit period
- " rcall uartDelay\n" // Wait 0.25 bit period
- " rcall uartDelay\n" // Wait 0.25 bit period
- " clc\n"
- " in r23,%[pin]\n"
- " and r23, %[mask]\n"
- " breq 2f\n"
- " sec\n"
- "2: ror %0\n"
- " dec %[count]\n"
- " breq 3f\n"
- " rjmp 1b\n"
- "3: rcall uartDelay\n" // Wait 0.25 bit period
- " rcall uartDelay\n" // Wait 0.25 bit period
- :
- "=r" (ch)
- :
- "0" ((uint8_t)0),
- [count] "r" ((uint8_t)8),
- [pin] "I" (_SFR_IO_ADDR(ANALOG_COMP_PIN)),
- [mask] "r" (Serial._rxmask)
- :
- "r23",
- "r24",
- "r25"
- );
- return ch;
- }
- void uartDelay() {
- __asm__ __volatile__ (
- "mov r25,%[count]\n"
- "1:dec r25\n"
- "brne 1b\n"
- "ret\n"
- ::[count] "r" ((uint8_t)Serial._delayCount)
- );
- }
- #if !defined (ANALOG_COMP_vect) && defined(ANA_COMP_vect)
- //rename the vector so we can use it.
- #define ANALOG_COMP_vect ANA_COMP_vect
- #elif !defined (ANALOG_COMP_vect)
- #error Tiny Software Serial cannot find the Analog comparator interrupt vector!
- #endif
- ISR(ANALOG_COMP_vect){
- char ch = getch(); //read in the character softwarily - I know its not a word, but it sounded cool, so you know what: #define softwarily 1
- store_char(ch, Serial._rx_buffer);
- sbi(ACSR,ACI); //clear the flag.
- }
- }
- soft_ring_buffer rx_buffer = { { 0 }, 0, 0 };
- // Constructor ////////////////////////////////////////////////////////////////
- TinySoftwareSerial::TinySoftwareSerial(soft_ring_buffer *rx_buffer, uint8_t txBit, uint8_t rxBit)
- {
- _rx_buffer = rx_buffer;
- _rxmask = _BV(rxBit);
- _txmask = _BV(txBit);
- _txunmask = ~_txmask;
- _delayCount = 0;
- }
- // Public Methods //////////////////////////////////////////////////////////////
- void TinySoftwareSerial::begin(long baud)
- {
- long tempDelay = (((F_CPU/baud)-39)/12);
- if ((tempDelay > 255) || (tempDelay <= 0)){
- end(); //Cannot start as it would screw up uartDelay().
- }
- _delayCount = (uint8_t)tempDelay;
- cbi(ACSR,ACIE); //turn off the comparator interrupt to allow change of ACD
- #ifdef ACBG
- sbi(ACSR,ACBG); //enable the internal bandgap reference - used instead of AIN0 to allow it to be used for TX.
- #endif
- cbi(ACSR,ACD); //turn on the comparator for RX
- #ifdef ACIC
- cbi(ACSR,ACIC); //prevent the comparator from affecting timer1 - just to be safe.
- #endif
- sbi(ACSR,ACIS1); //interrupt on rising edge (this means RX has gone from Mark state to Start bit state).
- sbi(ACSR,ACIS0);
- //Setup the pins in case someone messed with them.
- ANALOG_COMP_DDR &= ~_rxmask; //set RX to an input
- ANALOG_COMP_PORT |= _rxmask; //enable pullup on RX pin - to prevent accidental interrupt triggers.
- ANALOG_COMP_DDR |= _txmask; //set TX to an output.
- ANALOG_COMP_PORT |= _txmask; //set TX pin high
- sbi(ACSR,ACI); //clear the flag.
- sbi(ACSR,ACIE); //turn on the comparator interrupt to allow us to use it for RX
- #ifdef ACSRB
- ACSRB = 0; //Use AIN0 as +, AIN1 as -, no hysteresis - just like ones without this register.
- #endif
- }
- void TinySoftwareSerial::end()
- {
- sbi(ACSR,ACI); //clear the flag.
- cbi(ACSR,ACIE); //turn off the comparator interrupt to allow change of ACD, and because it needs to be turned off now too!
- #ifdef ACBG
- cbi(ACSR,ACBG); //disable the bandgap reference
- #endif
- sbi(ACSR,ACD); //turn off the comparator to save power
- _delayCount = 0;
- _rx_buffer->head = _rx_buffer->tail;
- }
- int TinySoftwareSerial::available(void)
- {
- return (unsigned int)(SERIAL_BUFFER_SIZE + _rx_buffer->head - _rx_buffer->tail) % SERIAL_BUFFER_SIZE;
- }
- void store_char(unsigned char c, soft_ring_buffer *buffer)
- {
- int i = (unsigned int)(buffer->head + 1) % SERIAL_BUFFER_SIZE;
- // if we should be storing the received character into the location
- // just before the tail (meaning that the head would advance to the
- // current location of the tail), we're about to overflow the buffer
- // and so we don't write the character or advance the head.
- if (i != buffer->tail) {
- buffer->buffer[buffer->head] = c;
- buffer->head = i;
- }
- }
- int TinySoftwareSerial::peek(void)
- {
- if (_rx_buffer->head == _rx_buffer->tail) {
- return -1;
- } else {
- return _rx_buffer->buffer[_rx_buffer->tail];
- }
- }
- int TinySoftwareSerial::read(void)
- {
- // if the head isn't ahead of the tail, we don't have any characters
- if (_rx_buffer->head == _rx_buffer->tail) {
- return -1;
- } else {
- unsigned char c = _rx_buffer->buffer[_rx_buffer->tail];
- _rx_buffer->tail = (unsigned int)(_rx_buffer->tail + 1) % SERIAL_BUFFER_SIZE;
- return c;
- }
- }
- size_t TinySoftwareSerial::write(uint8_t ch)
- {
- uint8_t oldSREG = SREG;
- cli(); //Prevent interrupts from breaking the transmission. Note: TinySoftwareSerial is half duplex.
- //it can either receive or send, not both (because receiving requires an interrupt and would stall transmission
- __asm__ __volatile__ (
- " com %[ch]\n" // ones complement, carry set
- " sec\n"
- "1: brcc 2f\n"
- " in r23,%[uartPort] \n"
- " and r23,%[uartUnmask]\n"
- " out %[uartPort],r23 \n"
- " rjmp 3f\n"
- "2: in r23,%[uartPort] \n"
- " or r23,%[uartMask]\n"
- " out %[uartPort],r23 \n"
- " nop\n"
- "3: rcall uartDelay\n"
- " rcall uartDelay\n"
- " rcall uartDelay\n"
- " rcall uartDelay\n"
- " lsr %[ch]\n"
- " dec %[count]\n"
- " brne 1b\n"
- :
- :
- [ch] "r" (ch),
- [count] "r" ((uint8_t)10),
- [uartPort] "I" (_SFR_IO_ADDR(ANALOG_COMP_PORT)),
- [uartMask] "r" (_txmask),
- [uartUnmask] "r" (_txunmask)
- : "r23",
- "r24",
- "r25"
- );
- SREG = oldSREG;
- return 1;
- }
- void TinySoftwareSerial::flush()
- {
- }
- TinySoftwareSerial::operator bool() {
- return true;
- }
- // Preinstantiate Objects //////////////////////////////////////////////////////
- #ifndef ANALOG_COMP_DDR
- #error Please define ANALOG_COMP_DDR in the pins_arduino.h file!
- #endif
- #ifndef ANALOG_COMP_PORT
- #error Please define ANALOG_COMP_PORT in the pins_arduino.h file!
- #endif
- #ifndef ANALOG_COMP_PIN
- #error Please define ANALOG_COMP_PIN in the pins_arduino.h file!
- #endif
- #ifndef ANALOG_COMP_AIN0_BIT
- #error Please define ANALOG_COMP_AIN0_BIT in the pins_arduino.h file!
- #endif
- #ifndef ANALOG_COMP_AIN1_BIT
- #error Please define ANALOG_COMP_AIN1_BIT in the pins_arduino.h file!
- #endif
- TinySoftwareSerial Serial(&rx_buffer, ANALOG_COMP_AIN0_BIT, ANALOG_COMP_AIN1_BIT);
- #endif // whole file
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