Optimise Endpoint_ConfigureEndpoint_Prv() function to produce smaller code when CONTR...

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

diff --git a/Projects/XPLAINBridge/Lib/SoftUART.c b/Projects/XPLAINBridge/Lib/SoftUART.c
index 18d5c01..b96b45f 100644 (file)
--- a/Projects/XPLAINBridge/Lib/SoftUART.c
+++ b/Projects/XPLAINBridge/Lib/SoftUART.c
@@ -39,86 +39,114 @@
 
 #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);

 
 

-/* 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
+       /* 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);

 
 

-       RX_Data    = 0;                                                 // clear bit storage
-       RX_BitMask = (1 << 0);                                  // bit mask
+       /* Setup reception timer compare ISR */
+       TIMSK1 = (1 << OCIE1A);

 
 

-       TIFR2 = (1 << OCF2A);                                   // clear pending interrupt
+       /* Setup transmission timer compare ISR and start the timer */
+       TIMSK3 = (1 << OCIE3A);
+       TCCR3B = ((1 << CS30) | (1 << WGM32));
+}

 
 

-       if (!(SRXPIN & (1 << SRX)))                             // still low
+/** ISR to detect the start of a bit being sent to the software UART. */
+ISR(INT0_vect, ISR_BLOCK)
+{
+       /* Reset the number of reception bits remaining counter */
+       RX_BitsRemaining = 8;
+       
+       /* Reset the bit reception timer */
+       TCNT1 = 0;
+
+       /* 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;

        }
        }

-} 
+}