X-Git-Url: http://git.linex4red.de/pub/USBasp.git/blobdiff_plain/8d993afc5388c5f3d0ff568c607f7fed6bb7390e..a8b66f318dda3cc18dfcedaa3af3d01ab68b82e8:/Projects/XPLAINBridge/Lib/SoftUART.c?ds=inline diff --git a/Projects/XPLAINBridge/Lib/SoftUART.c b/Projects/XPLAINBridge/Lib/SoftUART.c index ff152e7eb..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 @@ -45,116 +45,109 @@ 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; -/** Initializes the software UART, ready for data transmission and reception into the global ring buffers. */ +/** Initialises the software UART, ready for data transmission and reception into the global ring buffers. */ void SoftUART_Init(void) { - /* Set TX pin to output high, enable RX pullup */ + /* 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 incomming start bits that signal the start of a byte */ + /* Enable INT0 for the detection of incoming start bits that signal the start of a byte */ EICRA = (1 << ISC01); EIMSK = (1 << INT0); - /* Ensure that when the timer is enabled the transmission ISR runs immediately */ - OCR1B = TCNT1 + 1; - - /* Start timer 1 with transmission channel force-enabled so that it will immediatly fire */ - TCCR1C = (1 << FOC1B); - TIMSK1 = (1 << OCIE1B); - TCCR1B = (1 << CS10); + /* 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(INT0_vect, ISR_BLOCK) { - /* Set reception channel to fire 1.5 bits past the beginning of the start bit */ - OCR1A = TCNT1 + ((BIT_TIME * 3) / 2); - - /* Clear the received data temporary variable, reset the current received bit position mask */ - RX_Data = 0; - RX_BitMask = (1 << 0); + /* Reset the number of reception bits remaining counter */ + RX_BitsRemaining = 8; - /* Clear reception channel ISR flag in case it is pending */ - TIFR1 = (1 << OCF1A); + /* Reset the bit reception timer */ + TCNT1 = 0; - /* Check that the start bit is still low to prevent noise from triggering a reception */ + /* Check to see that the pin is still low (prevents glitches from starting a frame reception) */ if (!(SRXPIN & (1 << SRX))) - { - /* Still low, enable both send and receive channels */ - TIMSK1 = (1 << OCIE1A) | (1 << OCIE1B); - - /* Clear the start bit detection ISR flag if it is pending */ - 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(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 = (1 << OCIE1B); - EIMSK |= (1 << INT0); - EIFR = (1 << INTF0); + /* 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(TIMER3_COMPA_vect, ISR_BLOCK) { - /* Move the transmission ISR compare position one bit ahead */ - OCR1B += 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) + else if (!(RX_BitsRemaining) && !(RingBuffer_IsEmpty(&USBtoUART_Buffer))) { + /* 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; } -} +} +