Major changes to the XPLAINBridge software UART code for performance and reliability...

diff --git a/LUFA/ManPages/ChangeLog.txt b/LUFA/ManPages/ChangeLog.txt
index 0a2f43a..8164f30 100644 (file)
--- a/LUFA/ManPages/ChangeLog.txt
+++ b/LUFA/ManPages/ChangeLog.txt
@@ -27,6 +27,7 @@
   *  - The USB_Device_IsRemoteWakeupSent() and USB_Device_IsUSBSuspended() macros have been deleted, as they are now obsolete
   *  - Rewrote the implementation of the SwapEndian_16() and SwapEndian_32() functions so that they compile down in most instances to
   *    minimal loads and stores rather than complicated shifts
+  *  - The software UART in the XPLAINBridge has been largely altered to try to improve upon its performance and reliability
   *
   *  <b>Fixed:</b>
   *  - Fixed AVRISP project sending a LOAD EXTENDED ADDRESS command to 128KB AVRs after programming or reading from

diff --git a/Projects/XPLAINBridge/Lib/SoftUART.c b/Projects/XPLAINBridge/Lib/SoftUART.c
index 02223af..458a505 100644 (file)
--- a/Projects/XPLAINBridge/Lib/SoftUART.c
+++ b/Projects/XPLAINBridge/Lib/SoftUART.c
@@ -45,8 +45,8 @@ static uint8_t TX_BitsRemaining;
 /** Temporary data variable to hold the byte being transmitted as it is shifted out */
 static uint8_t TX_Data;
 
-/** Current bit mask of the bit being shifted into the received data byte */
-static uint8_t RX_BitMask;
+/** 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;
@@ -63,89 +63,83 @@ void SoftUART_Init(void)
        EICRA  = (1 << ISC01);
        EIMSK  = (1 << INT0);
 
-       /* Start software UART transmission and reception timers */
+       /* Set reception timer compare period and enable compare ISR */
+       OCR1A  = BIT_TIME;
+       TIMSK1 = (1 << OCIE1A);
+
+       /* Set transmission timer compare period, enable compare ISR and start the timer */
+       OCR3A  = BIT_TIME;
        TIMSK3 = (1 << OCIE3A);
-       TCCR3B = (1 << CS30);
-       TCCR1B = (1 << CS10);
+       TCCR3B = ((1 << CS30) | (1 << WGM32));
 }
 
 /** ISR to detect the start of a bit being sent to the software UART. */
 ISR(INT0_vect, ISR_BLOCK)
 {
-       /* Set reception channel to fire 1.5 bits past the beginning of the start bit */
-       OCR1A = TCNT1 + (BIT_TIME + (BIT_TIME / 2));
-
-       /* Clear the received data temporary variable, reset the current received bit position mask */
-       RX_Data    = 0;
-       RX_BitMask = (1 << 0);
+       /* Reset and start the reception timer */
+       TCNT1  = 0;
+       TCCR1B = ((1 << CS10) | (1 << WGM12));
 
-       /* Clear reception channel ISR flag and enable the bit reception ISR */
-       TIFR1  = (1 << OCF1A);
-       TIMSK1 = (1 << OCIE1A);         
+       /* Reset the number of reception bits remaining counter */
+       RX_BitsRemaining = 8;
 
        /* Disable start bit detection ISR while the next byte is received */
-       EIMSK &= ~(1 << INT0);
+       EIMSK = 0;
 }
 
 /** ISR to manage the reception of bits to the software UART. */
 ISR(TIMER1_COMPA_vect, ISR_BLOCK)
 {
-       /* Move the reception ISR compare position one bit ahead */
-       OCR1A += BIT_TIME;
+       /* Cache the current RX pin value for later checking */
+       uint8_t SRX_Cached = (SRXPIN & (1 << SRX));
 
        /* Check if reception has finished */
-       if (RX_BitMask)
+       if (RX_BitsRemaining)
        {
-               /* Store next bit into the received data variable */
-               if (SRXPIN & (1 << SRX))
-                 RX_Data |= RX_BitMask;
-
                /* Shift the current received bit mask to the next bit position */
-               RX_BitMask <<= 1;
+               RX_Data >>= 1;
+               RX_BitsRemaining--;
+
+               /* Store next bit into the received data variable */
+               if (SRX_Cached)
+                 RX_Data |= (1 << 7);
        }
        else
        {
-               /* Reception complete, store the received byte */
-               RingBuffer_Insert(&UARTtoUSB_Buffer, RX_Data);
-       
-               /* Disable the reception ISR as all data has now been received, re-enable start bit detection ISR */
-               TIMSK1 = 0;
+               /* 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 via the software UART. */
 ISR(TIMER3_COMPA_vect, ISR_NOBLOCK)
 {
-       /* Move the transmission ISR compare position one bit ahead */
-       OCR3A += BIT_TIME;
-
        /* Check if transmission has finished */
        if (TX_BitsRemaining)
        {
-               /* Check if we are sending a data bit, or the start bit */
-               if (--TX_BitsRemaining != 9)
-               {
-                       /* 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
-                         STXPORT |=  (1 << STX);
-
-                       /* Shift the transmission byte to move the next bit into position */
-                       TX_Data >>= 1;
-               }
+               /* 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
-               {
-                       /* Start bit - keep TX line low */
-                       STXPORT &= ~(1 << STX);
-               }
+                 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)
        {
+               /* 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 = 10;
+               TX_Data          = ~RingBuffer_Remove(&USBtoUART_Buffer);
+               TX_BitsRemaining = 9;
        }
-} 
+}

diff --git a/Projects/XPLAINBridge/Lib/SoftUART.h b/Projects/XPLAINBridge/Lib/SoftUART.h
index a685a6d..a107d48 100644 (file)
--- a/Projects/XPLAINBridge/Lib/SoftUART.h
+++ b/Projects/XPLAINBridge/Lib/SoftUART.h
@@ -43,7 +43,7 @@
 
        /* Macros: */
                #define BAUD       9600
-               #define BIT_TIME   ((F_CPU + (BAUD / 2)) / BAUD)
+               #define BIT_TIME   ((F_CPU / BAUD) - 1)
 
                #define SRX        PD0
                #define SRXPIN     PIND

diff --git a/Projects/XPLAINBridge/XPLAINBridge.c b/Projects/XPLAINBridge/XPLAINBridge.c
index 4ba9fd9..c08dfe9 100644 (file)
--- a/Projects/XPLAINBridge/XPLAINBridge.c
+++ b/Projects/XPLAINBridge/XPLAINBridge.c
@@ -76,7 +76,6 @@ RingBuff_t UARTtoUSB_Buffer;
 int main(void)
 {
        SetupHardware();
-       V2Protocol_Init();
 
        RingBuffer_InitBuffer(&USBtoUART_Buffer);
        RingBuffer_InitBuffer(&UARTtoUSB_Buffer);
@@ -127,9 +126,15 @@ void UARTBridge_Task(void)
        if (CDC_Device_BytesReceived(&VirtualSerial_CDC_Interface))
          RingBuffer_Insert(&USBtoUART_Buffer, CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface));
        
-       /* Read bytes from the UART receive buffer into the USB IN endpoint */
-       if (UARTtoUSB_Buffer.Count)
-         CDC_Device_SendByte(&VirtualSerial_CDC_Interface, RingBuffer_Remove(&UARTtoUSB_Buffer));
+       /* Check if the software UART flush timer has expired */
+       if (TIFR0 & (1 << TOV0))
+       {
+               TIFR0 |= (1 << TOV0);
+
+               /* Read bytes from the UART receive buffer into the USB IN endpoint */
+               while (UARTtoUSB_Buffer.Count)
+                 CDC_Device_SendByte(&VirtualSerial_CDC_Interface, RingBuffer_Remove(&UARTtoUSB_Buffer));
+       }
 
        CDC_Device_USBTask(&VirtualSerial_CDC_Interface);
 }
@@ -174,6 +179,9 @@ void EVENT_USB_Device_ConfigurationChanged(void)
        if (CurrentFirmwareMode == MODE_USART_BRIDGE)
        {
                EndpointConfigSuccess &= CDC_Device_ConfigureEndpoints(&VirtualSerial_CDC_Interface);
+
+               /* Configure the UART flush timer */
+               TCCR0B = ((1 << CS02) | (1 << CS00));
        }
        else
        {
@@ -186,6 +194,9 @@ void EVENT_USB_Device_ConfigurationChanged(void)
                                                                    ENDPOINT_DIR_IN, AVRISP_DATA_EPSIZE,
                                                                    ENDPOINT_BANK_SINGLE);
                #endif
+       
+               /* Configure the V2 protocol packet handler */
+               V2Protocol_Init();
        }
 
        if (EndpointConfigSuccess)