SerialHalfDuplex.cpp

00001  /* mbed Microcontroller Library
00002  * Copyright (c) 2006-2012 ARM Limited
00003  *
00004  * Permission is hereby granted, free of charge, to any person obtaining a copy
00005  * of this software and associated documentation files (the "Software"), to deal
00006  * in the Software without restriction, including without limitation the rights
00007  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
00008  * copies of the Software, and to permit persons to whom the Software is
00009  * furnished to do so, subject to the following conditions:
00010  *
00011  * The above copyright notice and this permission notice shall be included in
00012  * all copies or substantial portions of the Software.
00013  *
00014  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00015  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
00016  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
00017  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
00018  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
00019  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
00020  * SOFTWARE.
00021  *
00022  * NOTE: This is an unsupported legacy untested library.
00023  */
00024 #include "SerialHalfDuplex.h"
00025  
00026 #if DEVICE_SERIAL
00027  
00028 #include "pinmap.h"
00029 #include "serial_api.h"
00030 #include "gpio_api.h"
00031  
00032 namespace mbed {
00033  
00034 SerialHalfDuplex::SerialHalfDuplex(PinName tx, PinName rx, const char *name)
00035     : Serial(tx, rx, name) {
00036     _txpin = tx;
00037     
00038     // set as input 
00039     gpio_set(_txpin); 
00040     pin_mode(_txpin, PullNone); // no pull
00041     pin_function(_txpin, 0);    // set as gpio
00042 }
00043  
00044 // To transmit a byte in half duplex mode:
00045 // 1. Disable interrupts, so we don't trigger on loopback byte
00046 // 2. Set tx pin to UART out
00047 // 3. Transmit byte as normal
00048 // 4. Read back byte from looped back tx pin - this both confirms that the
00049 //    transmit has occurred, and also clears the byte from the buffer.
00050 // 5. Return pin to input mode
00051 // 6. Re-enable interrupts
00052  
00053 int SerialHalfDuplex::_putc(int c) {
00054     int retc;
00055     
00056     // TODO: We should not disable all interrupts
00057     __disable_irq();
00058     
00059     serial_pinout_tx(_txpin);
00060     
00061     Serial::_putc(c);
00062     retc = Serial::getc();       // reading also clears any interrupt
00063     
00064     pin_function(_txpin, 0);
00065     
00066     __enable_irq();
00067     
00068     return retc;
00069 }
00070  
00071 int SerialHalfDuplex::_getc(void) {
00072     return Serial::_getc();
00073 }
00074  
00075 } // End namespace
00076  
00077 #endif