Major changes to the XPLAINBridge software UART code for performance and reliability. New code reduces the number of missed characters and misread characters.
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Dean Camera
parent
2b0d93c129
commit
229935184b
4 changed files with 61 additions and 55 deletions
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@ -45,8 +45,8 @@ static uint8_t TX_BitsRemaining;
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/** Temporary data variable to hold the byte being transmitted as it is shifted out */
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static uint8_t TX_Data;
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/** Current bit mask of the bit being shifted into the received data byte */
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static uint8_t RX_BitMask;
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/** Total number of bits remaining to be received in the current frame */
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static uint8_t RX_BitsRemaining;
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/** Temporary data variable to hold the byte being received as it is shifted in */
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static uint8_t RX_Data;
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@ -63,89 +63,83 @@ void SoftUART_Init(void)
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EICRA = (1 << ISC01);
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EIMSK = (1 << INT0);
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/* Start software UART transmission and reception timers */
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/* Set reception timer compare period and enable compare ISR */
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OCR1A = BIT_TIME;
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TIMSK1 = (1 << OCIE1A);
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/* Set transmission timer compare period, enable compare ISR and start the timer */
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OCR3A = BIT_TIME;
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TIMSK3 = (1 << OCIE3A);
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TCCR3B = (1 << CS30);
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TCCR1B = (1 << CS10);
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TCCR3B = ((1 << CS30) | (1 << WGM32));
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}
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/** ISR to detect the start of a bit being sent to the software UART. */
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ISR(INT0_vect, ISR_BLOCK)
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{
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/* Set reception channel to fire 1.5 bits past the beginning of the start bit */
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OCR1A = TCNT1 + (BIT_TIME + (BIT_TIME / 2));
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/* Reset and start the reception timer */
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TCNT1 = 0;
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TCCR1B = ((1 << CS10) | (1 << WGM12));
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/* Clear the received data temporary variable, reset the current received bit position mask */
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RX_Data = 0;
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RX_BitMask = (1 << 0);
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/* Clear reception channel ISR flag and enable the bit reception ISR */
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TIFR1 = (1 << OCF1A);
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TIMSK1 = (1 << OCIE1A);
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/* Reset the number of reception bits remaining counter */
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RX_BitsRemaining = 8;
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/* Disable start bit detection ISR while the next byte is received */
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EIMSK &= ~(1 << INT0);
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EIMSK = 0;
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}
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/** ISR to manage the reception of bits to the software UART. */
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ISR(TIMER1_COMPA_vect, ISR_BLOCK)
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{
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/* Move the reception ISR compare position one bit ahead */
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OCR1A += BIT_TIME;
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/* Cache the current RX pin value for later checking */
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uint8_t SRX_Cached = (SRXPIN & (1 << SRX));
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/* Check if reception has finished */
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if (RX_BitMask)
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if (RX_BitsRemaining)
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{
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/* Store next bit into the received data variable */
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if (SRXPIN & (1 << SRX))
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RX_Data |= RX_BitMask;
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/* Shift the current received bit mask to the next bit position */
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RX_BitMask <<= 1;
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RX_Data >>= 1;
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RX_BitsRemaining--;
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/* Store next bit into the received data variable */
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if (SRX_Cached)
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RX_Data |= (1 << 7);
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}
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else
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{
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/* Reception complete, store the received byte */
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RingBuffer_Insert(&UARTtoUSB_Buffer, RX_Data);
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/* Disable the reception ISR as all data has now been received, re-enable start bit detection ISR */
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TIMSK1 = 0;
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/* Disable the reception timer as all data has now been received, re-enable start bit detection ISR */
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TCCR1B = 0;
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EIFR = (1 << INTF0);
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EIMSK = (1 << INT0);
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/* Reception complete, store the received byte if stop bit valid */
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if (SRX_Cached)
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RingBuffer_Insert(&UARTtoUSB_Buffer, RX_Data);
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}
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}
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/** ISR to manage the transmission of bits via the software UART. */
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ISR(TIMER3_COMPA_vect, ISR_NOBLOCK)
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{
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/* Move the transmission ISR compare position one bit ahead */
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OCR3A += BIT_TIME;
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/* Check if transmission has finished */
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if (TX_BitsRemaining)
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{
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/* Check if we are sending a data bit, or the start bit */
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if (--TX_BitsRemaining != 9)
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{
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/* Set the TX line to the value of the next bit in the byte to send */
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if (TX_Data & (1 << 0))
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STXPORT &= ~(1 << STX);
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else
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STXPORT |= (1 << STX);
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/* Shift the transmission byte to move the next bit into position */
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TX_Data >>= 1;
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}
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/* Set the TX line to the value of the next bit in the byte to send */
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if (TX_Data & (1 << 0))
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STXPORT &= ~(1 << STX);
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else
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{
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/* Start bit - keep TX line low */
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STXPORT &= ~(1 << STX);
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}
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STXPORT |= (1 << STX);
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/* Shift the transmission byte to move the next bit into position and decrement the bits remaining counter */
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TX_Data >>= 1;
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TX_BitsRemaining--;
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}
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else if (USBtoUART_Buffer.Count)
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{
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/* Start bit - TX line low */
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STXPORT &= ~(1 << STX);
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/* Transmission complete, get the next byte to send (if available) */
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TX_Data = ~RingBuffer_Remove(&USBtoUART_Buffer);
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TX_BitsRemaining = 10;
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TX_Data = ~RingBuffer_Remove(&USBtoUART_Buffer);
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TX_BitsRemaining = 9;
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}
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}
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}
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@ -43,7 +43,7 @@
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/* Macros: */
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#define BAUD 9600
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#define BIT_TIME ((F_CPU + (BAUD / 2)) / BAUD)
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#define BIT_TIME ((F_CPU / BAUD) - 1)
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#define SRX PD0
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#define SRXPIN PIND
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@ -76,7 +76,6 @@ RingBuff_t UARTtoUSB_Buffer;
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int main(void)
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{
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SetupHardware();
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V2Protocol_Init();
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RingBuffer_InitBuffer(&USBtoUART_Buffer);
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RingBuffer_InitBuffer(&UARTtoUSB_Buffer);
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@ -127,9 +126,15 @@ void UARTBridge_Task(void)
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if (CDC_Device_BytesReceived(&VirtualSerial_CDC_Interface))
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RingBuffer_Insert(&USBtoUART_Buffer, CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface));
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/* Read bytes from the UART receive buffer into the USB IN endpoint */
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if (UARTtoUSB_Buffer.Count)
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CDC_Device_SendByte(&VirtualSerial_CDC_Interface, RingBuffer_Remove(&UARTtoUSB_Buffer));
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/* Check if the software UART flush timer has expired */
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if (TIFR0 & (1 << TOV0))
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{
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TIFR0 |= (1 << TOV0);
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/* Read bytes from the UART receive buffer into the USB IN endpoint */
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while (UARTtoUSB_Buffer.Count)
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CDC_Device_SendByte(&VirtualSerial_CDC_Interface, RingBuffer_Remove(&UARTtoUSB_Buffer));
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}
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CDC_Device_USBTask(&VirtualSerial_CDC_Interface);
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}
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@ -174,6 +179,9 @@ void EVENT_USB_Device_ConfigurationChanged(void)
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if (CurrentFirmwareMode == MODE_USART_BRIDGE)
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{
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EndpointConfigSuccess &= CDC_Device_ConfigureEndpoints(&VirtualSerial_CDC_Interface);
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/* Configure the UART flush timer */
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TCCR0B = ((1 << CS02) | (1 << CS00));
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}
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else
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{
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@ -186,6 +194,9 @@ void EVENT_USB_Device_ConfigurationChanged(void)
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ENDPOINT_DIR_IN, AVRISP_DATA_EPSIZE,
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ENDPOINT_BANK_SINGLE);
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#endif
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/* Configure the V2 protocol packet handler */
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V2Protocol_Init();
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}
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if (EndpointConfigSuccess)
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