Add new more reliable software UART for the XPLAINBridge project by David...

Add new more reliable software UART for the XPLAINBridge project by David Prentice and Peter Danneger.

Projects/XPLAINBridge/Lib/SoftUART.c

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

Projects/XPLAINBridge/Lib/SoftUART.h

+/*
+             LUFA Library
+     Copyright (C) Dean Camera, 2009.
+              
+  dean [at] fourwalledcubicle [dot] com
+      www.fourwalledcubicle.com
+*/
+
+/*
+  Copyright 2009  David Prentice (david.prentice [at] farming [dot] uk)
+  Copyright 2009  Peter Danneger
+  Copyright 2009  Dean Camera (dean [at] fourwalledcubicle [dot] com)
+
+  Permission to use, copy, modify, and distribute this software
+  and its documentation for any purpose and without fee is hereby
+  granted, provided that the above copyright notice appear in all
+  copies and that both that the copyright notice and this
+  permission notice and warranty disclaimer appear in supporting
+  documentation, and that the name of the author not be used in
+  advertising or publicity pertaining to distribution of the
+  software without specific, written prior permission.
+
+  The author disclaim all warranties with regard to this
+  software, including all implied warranties of merchantability
+  and fitness.  In no event shall the author be liable for any
+  special, indirect or consequential damages or any damages
+  whatsoever resulting from loss of use, data or profits, whether
+  in an action of contract, negligence or other tortious action,
+  arising out of or in connection with the use or performance of
+  this software.
+*/
+
+#ifndef _SOFT_UART_
+#define _SOFT_UART_
+
+	/* Includes: */
+		#include <avr/io.h>
+		#include <avr/interrupt.h>
+		#include "SoftUART.h"
+
+	/* Macros: */
+		#define BAUD       9600
+		#define BIT_TIME   (uint16_t)((F_CPU + (BAUD / 2)) / BAUD)
+
+		#define SRX        PD0
+		#define SRXPIN     PIND
+		#define SRXPORT    PORTD
+
+		#define STX        PD1
+		#define STXPORT    PORTD
+		#define STXDDR     DDRD
+
+	/* Function Prototypes: */
+		unsigned char SoftUART_IsReady(void);
+		unsigned char SoftUART_TxByte(unsigned char c);
+		unsigned char SoftUART_IsReceived(void);
+		unsigned char SoftUART_RxByte(void);
+		void SoftUART_Init(void);
+
+#endif
\ No newline at end of file

Projects/XPLAINBridge/makefile

@@ -127,6 +127,7 @@ LUFA_OPTS += -D USE_STATIC_OPTIONS="(USB_DEVICE_OPT_FULLSPEED | USB_OPT_REG_ENAB
 SRC = $(TARGET).c                                                 \
 	  Descriptors.c                                               \
 	  Lib/RingBuff.c                                              \
+	  Lib/SoftUART.c                                              \
 	  $(LUFA_PATH)/LUFA/Drivers/USB/LowLevel/DevChapter9.c        \
 	  $(LUFA_PATH)/LUFA/Drivers/USB/LowLevel/Endpoint.c           \
 	  $(LUFA_PATH)/LUFA/Drivers/USB/LowLevel/Host.c               \
@@ -152,7 +153,7 @@ CPPSRC =
 #     Even though the DOS/Win* filesystem matches both .s and .S the same,
 #     it will preserve the spelling of the filenames, and gcc itself does
 #     care about how the name is spelled on its command-line.
-ASRC = Lib/SoftUART.S
+ASRC = 
 
 
 # Optimization level, can be [0, 1, 2, 3, s].