X-Git-Url: http://git.linex4red.de/pub/USBasp.git/blobdiff_plain/9c037a952f5aaf78c4e13398506cfa2d588bb449..55d7e1e65bccd6b4c44802cf971f39eb05e6e57a:/Projects/XPLAINBridge/Lib/SoftUART.c diff --git a/Projects/XPLAINBridge/Lib/SoftUART.c b/Projects/XPLAINBridge/Lib/SoftUART.c index 5e589f3d7..02223af98 100644 --- a/Projects/XPLAINBridge/Lib/SoftUART.c +++ b/Projects/XPLAINBridge/Lib/SoftUART.c @@ -30,102 +30,122 @@ this software. */ -#include "SoftUART.h" +/** \file + * + * Software UART for both data transmission and reception. This + * code continuously monitors the ring buffers set up by the main + * project source file and reads/writes data as it becomes available. + */ -volatile bool srx_done; -volatile uint8_t stx_count; -static uint8_t srx_data, srx_mask, srx_tmp, stx_data; +#include "SoftUART.h" -void SoftUART_TxByte(uint8_t Byte) -{ - while (stx_count); +/** Total number of bits remaining to be sent in the current frame */ +static uint8_t TX_BitsRemaining; - stx_data = ~Byte; - stx_count = 10; -} +/** Temporary data variable to hold the byte being transmitted as it is shifted out */ +static uint8_t TX_Data; -uint8_t SoftUART_RxByte(void) -{ - while (!(srx_done)); - srx_done = false; +/** Current bit mask of the bit being shifted into the received data byte */ +static uint8_t RX_BitMask; - return srx_data; -} +/** Temporary data variable to hold the byte being received as it is shifted in */ +static uint8_t RX_Data; +/** Initializes the software UART, ready for data transmission and reception into the global ring buffers. */ 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 = false; // nothing received - 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); + + /* Start software UART transmission and reception timers */ + TIMSK3 = (1 << OCIE3A); + TCCR3B = (1 << CS30); + TCCR1B = (1 << CS10); } -/* 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 + /* Set reception channel to fire 1.5 bits past the beginning of the start bit */ + OCR1A = TCNT1 + (BIT_TIME + (BIT_TIME / 2)); - srx_tmp = 0; // clear bit storage - srx_mask = 1; // bit mask + /* Clear the received data temporary variable, reset the current received bit position mask */ + RX_Data = 0; + RX_BitMask = (1 << 0); - TIFR2 = (1 << OCF2A); // clear pending interrupt + /* Clear reception channel ISR flag and enable the bit reception ISR */ + TIFR1 = (1 << OCF1A); + TIMSK1 = (1 << OCIE1A); - if (!(SRXPIN & (1 << SRX))) // still low - { - TIMSK2 = (1 << OCIE2A) | (1 << OCIE2B); // wait for first bit - EIMSK &= ~(1 << INT0); - } + /* Disable start bit detection ISR while the next byte is received */ + EIMSK &= ~(1 << INT0); } -/* 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 (srx_mask) + /* Move the reception ISR compare position one bit ahead */ + OCR1A += BIT_TIME; + + /* Check if reception has finished */ + if (RX_BitMask) { + /* Store next bit into the received data variable */ if (SRXPIN & (1 << SRX)) - srx_tmp |= srx_mask; + RX_Data |= RX_BitMask; - srx_mask <<= 1; - - OCR2A += BIT_TIME / 8; // next bit slice + /* Shift the current received bit mask to the next bit position */ + RX_BitMask <<= 1; } else { - srx_done = true; // 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 + /* 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; + EIFR = (1 << INTF0); + EIMSK = (1 << INT0); } } -/* 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_NOBLOCK) { - OCR2B += BIT_TIME / 8; // next bit slice + /* Move the transmission ISR compare position one bit ahead */ + OCR3A += BIT_TIME; - if (stx_count) + /* Check if transmission has finished */ + if (TX_BitsRemaining) { - if (--stx_count != 9) // no start bit + /* Check if we are sending a data bit, or the start bit */ + if (--TX_BitsRemaining != 9) { - if (!(stx_data & 1)) // test inverted data - TCCR2A = (1 << COM2B1) | (1 << COM2B0); + /* 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 - TCCR2A = (1 << COM2B1); + STXPORT |= (1 << STX); - stx_data >>= 1; // shift zero in from left + /* Shift the transmission byte to move the next bit into position */ + TX_Data >>= 1; } else { - TCCR2A = (1 << COM2B1); // START bit + /* Start bit - keep TX line low */ + STXPORT &= ~(1 << STX); } } + else if (USBtoUART_Buffer.Count) + { + /* Transmission complete, get the next byte to send (if available) */ + TX_Data = ~RingBuffer_Remove(&USBtoUART_Buffer); + TX_BitsRemaining = 10; + } }