diff options
Diffstat (limited to 'lib/lufa/Projects/XPLAINBridge/Lib/SoftUART.c')
| -rw-r--r-- | lib/lufa/Projects/XPLAINBridge/Lib/SoftUART.c | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/lib/lufa/Projects/XPLAINBridge/Lib/SoftUART.c b/lib/lufa/Projects/XPLAINBridge/Lib/SoftUART.c new file mode 100644 index 000000000..5c0e3c8cd --- /dev/null +++ b/lib/lufa/Projects/XPLAINBridge/Lib/SoftUART.c @@ -0,0 +1,156 @@ +/* + LUFA Library + Copyright (C) Dean Camera, 2017. + + dean [at] fourwalledcubicle [dot] com + www.lufa-lib.org +*/ + +/* + Copyright 2010 David Prentice (david.prentice [at] farming [dot] uk) + Copyright 2010 Peter Danneger + Copyright 2017 Dean Camera (dean [at] fourwalledcubicle [dot] com) + + 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 + 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 + software without specific, written prior permission. + + The author disclaims all warranties with regard to this + software, including all implied warranties of merchantability + and fitness. In no event shall the author be liable for any + special, indirect or consequential damages or any damages + whatsoever resulting from loss of use, data or profits, whether + in an action of contract, negligence or other tortious action, + arising out of or in connection with the use or performance of + this software. +*/ + +/** \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. + */ + +#include "SoftUART.h" + +/** 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; + + +/** Initializes 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 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_BLOCK) +{ + /* Reset the number of reception bits remaining counter */ + RX_BitsRemaining = 8; + + /* Reset the bit reception timer to -(1/2) of the total bit time, so that the first data bit is + * sampled mid way through the total bit time, making reception more robust. + */ + TCNT1 = -(OCR1A >> 1); + + /* Check to see that the pin is still low (prevents glitches from starting a frame reception) */ + if (!(SRXPIN & (1 << SRX))) + { + /* 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_BLOCK) +{ + /* Cache the current RX pin value for later checking */ + uint8_t SRX_Cached = (SRXPIN & (1 << SRX)); + + /* Check if reception has finished */ + if (RX_BitsRemaining) + { + /* Shift the current received bit mask to the next bit position */ + RX_Data >>= 1; + RX_BitsRemaining--; + + /* Store next bit into the received data variable */ + if (SRX_Cached) + RX_Data |= (1 << 7); + } + else + { + /* 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_BLOCK) +{ + /* Check if transmission has finished */ + if (TX_BitsRemaining) + { + /* 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 and decrement the bits remaining counter */ + TX_Data >>= 1; + TX_BitsRemaining--; + } + 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 = 9; + } +} + |