Add new more reliable software UART for the XPLAINBridge project by David Prentice and Peter Danneger.
Dean Camera
15 years ago
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fec31947a6
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/*
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LUFA Library
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Copyright (C) Dean Camera, 2009.
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dean [at] fourwalledcubicle [dot] com
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www.fourwalledcubicle.com
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*/
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/*
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Copyright 2009 David Prentice (david.prentice [at] farming [dot] uk)
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Copyright 2009 Peter Danneger
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Copyright 2009 Dean Camera (dean [at] fourwalledcubicle [dot] com)
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Permission to use, copy, modify, and distribute this software
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and its documentation for any purpose and without fee is hereby
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granted, provided that the above copyright notice appear in all
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||||
copies and that both that the copyright notice and this
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permission notice and warranty disclaimer appear in supporting
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documentation, and that the name of the author not be used in
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advertising or publicity pertaining to distribution of the
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software without specific, written prior permission.
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The author disclaim all warranties with regard to this
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software, including all implied warranties of merchantability
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and fitness. In no event shall the author be liable for any
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special, indirect or consequential damages or any damages
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whatsoever resulting from loss of use, data or profits, whether
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in an action of contract, negligence or other tortious action,
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arising out of or in connection with the use or performance of
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this software.
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*/
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#include "SoftUART.h"
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volatile uint8_t srx_done, stx_count;
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volatile uint8_t srx_data, srx_mask, srx_tmp, stx_data;
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unsigned char SoftUART_IsReady(void)
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{
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return !(stx_count);
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}
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unsigned char SoftUART_TxByte(unsigned char c)
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{
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while (stx_count);
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stx_data = ~c;
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stx_count = 10;
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return c;
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}
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unsigned char SoftUART_IsReceived(void)
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{
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return srx_done;
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}
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unsigned char SoftUART_RxByte(void)
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{
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while (!(srx_done));
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srx_done = 0;
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return srx_data;
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}
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void SoftUART_Init(void)
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{
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OCR2B = TCNT2 + 1; // force first compare
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TCCR2A = (1 << COM2B1) | (1 << COM2B0); // T1 mode 0
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TCCR2B = (1 << FOC2B) | (1 << CS21); // CLK/8, T1 mode 0
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TIMSK2 = (1 << OCIE2B); // enable tx and wait for start
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EICRA = (1 << ISC01); // -ve edge
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EIMSK = (1 << INT0); // enable INT0 interrupt
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stx_count = 0; // nothing to send
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srx_done = 0; // nothing received
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STXPORT |= 1 << STX; // TX output
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STXDDR |= 1 << STX; // TX output
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SRXPORT |= (1 << SRX); // pullup on INT0
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}
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/* ISR to detect the start of a bit being sent from the transmitter. */
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ISR(INT0_vect)
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{
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OCR2A = TCNT2 + (BIT_TIME / 8 * 3 / 2); // scan 1.5 bits after start
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srx_tmp = 0; // clear bit storage
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srx_mask = 1; // bit mask
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TIFR2 = (1 << OCF2A); // clear pending interrupt
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if (!(SRXPIN & (1 << SRX))) // still low
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{
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TIMSK2 = (1 << OCIE2A) | (1 << OCIE2B); // wait for first bit
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EIMSK &= ~(1 << INT0);
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}
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}
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/* ISR to manage the reception of bits to the transmitter. */
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ISR(TIMER2_COMPA_vect)
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{
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if (srx_mask)
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{
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if (SRXPIN & (1 << SRX))
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srx_tmp |= srx_mask;
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srx_mask <<= 1;
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OCR2A += BIT_TIME / 8; // next bit slice
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}
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else
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{
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srx_done = 1; // mark rx data valid
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srx_data = srx_tmp; // store rx data
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TIMSK2 = (1 << OCIE2B); // enable tx and wait for start
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EIMSK |= (1 << INT0); // enable START irq
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EIFR = (1 << INTF0); // clear any pending
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}
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}
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/* ISR to manage the transmission of bits to the receiver. */
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ISR(TIMER2_COMPB_vect)
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{
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OCR2B += BIT_TIME / 8; // next bit slice
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if (stx_count)
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{
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if (--stx_count != 9) // no start bit
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{
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if (!(stx_data & 1)) // test inverted data
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TCCR2A = (1 << COM2B1) | (1 << COM2B0);
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else
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TCCR2A = (1 << COM2B1);
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stx_data >>= 1; // shift zero in from left
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}
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else
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{
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TCCR2A = (1 << COM2B1); // START bit
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}
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}
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}
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@ -0,0 +1,60 @@
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/*
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LUFA Library
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Copyright (C) Dean Camera, 2009.
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dean [at] fourwalledcubicle [dot] com
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www.fourwalledcubicle.com
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*/
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/*
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Copyright 2009 David Prentice (david.prentice [at] farming [dot] uk)
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Copyright 2009 Peter Danneger
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Copyright 2009 Dean Camera (dean [at] fourwalledcubicle [dot] com)
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Permission to use, copy, modify, and distribute this software
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and its documentation for any purpose and without fee is hereby
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granted, provided that the above copyright notice appear in all
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||||
copies and that both that the copyright notice and this
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||||
permission notice and warranty disclaimer appear in supporting
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||||
documentation, and that the name of the author not be used in
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advertising or publicity pertaining to distribution of the
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software without specific, written prior permission.
|
||||
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The author disclaim all warranties with regard to this
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software, including all implied warranties of merchantability
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and fitness. In no event shall the author be liable for any
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special, indirect or consequential damages or any damages
|
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whatsoever resulting from loss of use, data or profits, whether
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in an action of contract, negligence or other tortious action,
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arising out of or in connection with the use or performance of
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this software.
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*/
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#ifndef _SOFT_UART_
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#define _SOFT_UART_
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/* Includes: */
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include "SoftUART.h"
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/* Macros: */
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#define BAUD 9600
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#define BIT_TIME (uint16_t)((F_CPU + (BAUD / 2)) / BAUD)
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#define SRX PD0
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#define SRXPIN PIND
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#define SRXPORT PORTD
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#define STX PD1
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#define STXPORT PORTD
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#define STXDDR DDRD
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/* Function Prototypes: */
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unsigned char SoftUART_IsReady(void);
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unsigned char SoftUART_TxByte(unsigned char c);
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unsigned char SoftUART_IsReceived(void);
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unsigned char SoftUART_RxByte(void);
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void SoftUART_Init(void);
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#endif
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