X-Git-Url: http://git.linex4red.de/pub/USBasp.git/blobdiff_plain/1c407b9669c0658ee9eb8b188818135ea04215e4..a8b66f318dda3cc18dfcedaa3af3d01ab68b82e8:/Projects/XPLAINBridge/Lib/SoftUART.c?ds=inline diff --git a/Projects/XPLAINBridge/Lib/SoftUART.c b/Projects/XPLAINBridge/Lib/SoftUART.c index c001c0787..7667bfa31 100644 --- 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 - www.fourwalledcubicle.com + www.lufa-lib.org */ /* @@ -11,13 +11,13 @@ 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 - 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 - 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 @@ -39,86 +39,115 @@ #include "SoftUART.h" -static uint8_t TX_BitsRemaining, TX_Data; -static uint8_t 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) { - OCR1B = TCNT1 + 1; // force first compare - TCCR1B = (1 << CS10); // CLK/1, T1 mode 0 - TCCR1C = (1 << FOC1B); - TIMSK1 = (1 << OCIE1B); // enable tx and wait for start - EICRA = (1 << ISC01); // -ve edge - EIMSK = (1 << INT0); // enable INT0 interrupt - - 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 to the software UART. */ -ISR(INT0_vect) +/** ISR to detect the start of a bit being sent to the software UART. */ +ISR(INT0_vect, ISR_BLOCK) { - OCR1A = TCNT1 + ((BIT_TIME * 3) / 2) - 1; // 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; - TIFR1 = (1 << OCF1A); // 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))) { - TIMSK1 = (1 << OCIE1A) | (1 << OCIE1B); // 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 software UART. */ -ISR(TIMER1_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--; - OCR1A += BIT_TIME; // next bit slice + /* Store next bit into the received data variable */ + if (SRX_Cached) + RX_Data |= (1 << 7); } else { - RingBuffer_Insert(&UARTtoUSB_Buffer, RX_Data); - - TIMSK1 = (1 << OCIE1B); // 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 via the software UART. */ -ISR(TIMER1_COMPB_vect) +/** ISR to manage the transmission of bits via the software UART. */ +ISR(TIMER3_COMPA_vect, ISR_BLOCK) { - OCR1B += BIT_TIME; // next bit slice - + /* Check if transmission has finished */ if (TX_BitsRemaining) { - if (--TX_BitsRemaining != 9) // no start bit - { - if (TX_Data & (1 << 0)) // test inverted data - STXPORT &= ~(1 << STX); - else - STXPORT = (1 << STX); - - 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 - { - 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) + 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; } -} +} +