Documentation improvements - put driver example code into its own section, fix incorr...

[pub/USBasp.git] / Projects / XPLAINBridge / Lib / SoftUART.c

diff --git a/Projects/XPLAINBridge/Lib/SoftUART.c b/Projects/XPLAINBridge/Lib/SoftUART.c
index 18d5c01..7667bfa 100644 (file)
--- a/Projects/XPLAINBridge/Lib/SoftUART.c
+++ b/Projects/XPLAINBridge/Lib/SoftUART.c
@@ -1,9 +1,9 @@
 /*
 /*

-                        LUFA Library
-        Copyright (C) Dean Camera, 2010.
-                         
+             LUFA Library
+     Copyright (C) Dean Camera, 2010.
+

   dean [at] fourwalledcubicle [dot] com
   dean [at] fourwalledcubicle [dot] com

-         www.fourwalledcubicle.com
+           www.lufa-lib.org

 */
 
 /*
 */
 
 /*


@@ -11,13 +11,13 @@
   Copyright 2010  Peter Danneger
   Copyright 2010  Dean Camera (dean [at] fourwalledcubicle [dot] com)
 
   Copyright 2010  Peter Danneger
   Copyright 2010  Dean Camera (dean [at] fourwalledcubicle [dot] com)
 

-  Permission to use, copy, modify, distribute, and sell this 
+  Permission to use, copy, modify, distribute, and sell this

   software and its documentation for any purpose is hereby granted
   software and its documentation for any purpose is hereby granted

-  without fee, provided that the above copyright notice appear in 
+  without fee, provided that the above copyright notice appear in

   all copies and that both that the copyright notice and this
   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 
+  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 without specific, written prior permission.
 
   The author disclaim all warranties with regard to this


@@ -39,86 +39,115 @@
 
 #include "SoftUART.h"
 
 
 #include "SoftUART.h"
 

-static uint8_t TX_BitsRemaining, TX_Data, RX_BitMask, RX_Data;
+/** Total number of bits remaining to be sent in the current frame */
+static uint8_t TX_BitsRemaining;
+
+/** Temporary data variable to hold the byte being transmitted as it is shifted out */
+static uint8_t TX_Data;
+
+/** Total number of bits remaining to be received in the current frame */
+static uint8_t RX_BitsRemaining;

 
 

+/** Temporary data variable to hold the byte being received as it is shifted in */
+static uint8_t RX_Data;
+
+/** Initialises the software UART, ready for data transmission and reception into the global ring buffers. */

 void SoftUART_Init(void)
 {
 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
-
-       TX_BitsRemaining = 0;                                   // nothing to send
-       STXPORT |= (1 << STX);                                  // TX output
-       STXDDR  |= (1 << STX);                                  // TX output
-       SRXPORT |= (1 << SRX);                                  // pullup on INT0
+       /* Set TX pin to output high, enable RX pull-up */
+       STXPORT |= (1 << STX);
+       STXDDR  |= (1 << STX);
+       SRXPORT |= (1 << SRX);
+
+       /* Enable INT0 for the detection of incoming start bits that signal the start of a byte */
+       EICRA  = (1 << ISC01);
+       EIMSK  = (1 << INT0);
+
+       /* Set the transmission and reception timer compare values for the default baud rate */
+       SoftUART_SetBaud(9600);
+
+       /* Setup reception timer compare ISR */
+       TIMSK1 = (1 << OCIE1A);
+
+       /* Setup transmission timer compare ISR and start the timer */
+       TIMSK3 = (1 << OCIE3A);
+       TCCR3B = ((1 << CS30) | (1 << WGM32));

 }
 
 }
 

-/* ISR to detect the start of a bit being sent from the transmitter. */
-ISR(INT0_vect)
+/** ISR to detect the start of a bit being sent to the software UART. */
+ISR(INT0_vect, ISR_BLOCK)

 {
 {

-       OCR2A = TCNT2 + (BIT_TIME / 8 * 3 / 2); // scan 1.5 bits after start
-
-       RX_Data    = 0;                                                 // clear bit storage
-       RX_BitMask = (1 << 0);                                  // bit mask
+       /* Reset the number of reception bits remaining counter */
+       RX_BitsRemaining = 8;

 
 

-       TIFR2 = (1 << OCF2A);                                   // clear pending interrupt
+       /* Reset the bit reception timer */
+       TCNT1 = 0;

 
 

-       if (!(SRXPIN & (1 << SRX)))                             // still low
+       /* Check to see that the pin is still low (prevents glitches from starting a frame reception) */
+       if (!(SRXPIN & (1 << SRX)))

        {
        {

-               TIMSK2 = (1 << OCIE2A) | (1 << OCIE2B); // wait for first bit
-               EIMSK &= ~(1 << INT0);
+               /* Disable start bit detection ISR while the next byte is received */
+               EIMSK = 0;
+
+               /* Start the reception timer */
+               TCCR1B = ((1 << CS10) | (1 << WGM12));

        }
 }
 
        }
 }
 

-/* ISR to manage the reception of bits to the transmitter. */
-ISR(TIMER2_COMPA_vect)
+/** ISR to manage the reception of bits to the software UART. */
+ISR(TIMER1_COMPA_vect, ISR_BLOCK)

 {
 {

-       if (RX_BitMask)
-       {
-               if (SRXPIN & (1 << SRX))
-                 RX_Data |= RX_BitMask;
+       /* Cache the current RX pin value for later checking */
+       uint8_t SRX_Cached = (SRXPIN & (1 << SRX));

 
 

-               RX_BitMask <<= 1;
+       /* Check if reception has finished */
+       if (RX_BitsRemaining)
+       {
+               /* Shift the current received bit mask to the next bit position */
+               RX_Data >>= 1;
+               RX_BitsRemaining--;

 
 

-               OCR2A += BIT_TIME / 8;                          // next bit slice
+               /* Store next bit into the received data variable */
+               if (SRX_Cached)
+                 RX_Data |= (1 << 7);

        }
        else
        {
        }
        else
        {

-               RingBuffer_Insert(&UARTtoUSB_Buffer, RX_Data);
-
-               TIMSK2    = (1 << OCIE2B);                      // enable tx and wait for start
-               EIMSK    |= (1 << INT0);                        // enable START irq
-               EIFR      = (1 << INTF0);                       // clear any pending
+               /* Disable the reception timer as all data has now been received, re-enable start bit detection ISR */
+               TCCR1B = 0;
+               EIFR   = (1 << INTF0);
+               EIMSK  = (1 << INT0);
+
+               /* Reception complete, store the received byte if stop bit valid */
+               if (SRX_Cached)
+                 RingBuffer_Insert(&UARTtoUSB_Buffer, RX_Data);

        }
 }
 
        }
 }
 

-/* ISR to manage the transmission of bits to the receiver. */
-ISR(TIMER2_COMPB_vect)
+/** ISR to manage the transmission of bits via the software UART. */
+ISR(TIMER3_COMPA_vect, ISR_BLOCK)

 {
 {

-       OCR2B += BIT_TIME / 8;                                  // next bit slice
-
+       /* Check if transmission has finished */

        if (TX_BitsRemaining)
        {
        if (TX_BitsRemaining)
        {

-               if (--TX_BitsRemaining != 9)            // no start bit
-               {
-                       if (TX_Data & (1 << 0))                 // test inverted data
-                         TCCR2A = (1 << COM2B1);
-                       else
-                         TCCR2A = (1 << COM2B1) | (1 << COM2B0);
-
-                       TX_Data >>= 1;                                  // shift zero in from left
-               }
+               /* Set the TX line to the value of the next bit in the byte to send */
+               if (TX_Data & (1 << 0))
+                 STXPORT &= ~(1 << STX);

                else
                else

-               {
-                       TCCR2A = (1 << COM2B1);                 // START bit
-               }
+                 STXPORT |=  (1 << STX);
+
+               /* Shift the transmission byte to move the next bit into position and decrement the bits remaining counter */
+               TX_Data >>= 1;
+               TX_BitsRemaining--;

        }
        }

-       else if (USBtoUART_Buffer.Count)
+       else if (!(RX_BitsRemaining) && !(RingBuffer_IsEmpty(&USBtoUART_Buffer)))

        {
        {

-               TX_Data = ~RingBuffer_Remove(&USBtoUART_Buffer);
-               TX_BitsRemaining = 10;
+               /* Start bit - TX line low */
+               STXPORT &= ~(1 << STX);
+
+               /* Transmission complete, get the next byte to send (if available) */
+               TX_Data          = ~RingBuffer_Remove(&USBtoUART_Buffer);
+               TX_BitsRemaining = 9;

        }
        }

-} 
+}
+