tmk_core/tool/mbed/mbed-sdk/libraries/tests/libs/SerialHalfDuplex/SerialHalfDuplex.cpp

   1 /* mbed Microcontroller Library - SerialHalfDuplex
   2  * Copyright (c) 2010-2011 ARM Limited. All rights reserved.
   3  */
   4 #include "SerialHalfDuplex.h"
   5
   6 #if DEVICE_SERIAL
   7
   8 #include "pinmap.h"
   9 #include "serial_api.h"
  10
  11 namespace mbed {
  12
  13 SerialHalfDuplex::SerialHalfDuplex(PinName tx, PinName rx)
  14     : Serial(tx, rx) {
  15
  16     gpio_init(&gpio, tx, PIN_INPUT);
  17     gpio_mode(&gpio, PullNone); // no pull
  18 }
  19
  20 // To transmit a byte in half duplex mode:
  21 // 1. Disable interrupts, so we don't trigger on loopback byte
  22 // 2. Set tx pin to UART out
  23 // 3. Transmit byte as normal
  24 // 4. Read back byte from looped back tx pin - this both confirms that the
  25 //    transmit has occurred, and also clears the byte from the buffer.
  26 // 5. Return pin to input mode
  27 // 6. Re-enable interrupts
  28 int SerialHalfDuplex::_putc(int c) {
  29     int retc;
  30
  31     // TODO: We should not disable all interrupts
  32     __disable_irq();
  33
  34     serial_pinout_tx(gpio.pin);
  35
  36     Serial::_putc(c);
  37     retc = Serial::getc();       // reading also clears any interrupt
  38
  39     pin_function(gpio.pin, 0);
  40
  41     __enable_irq();
  42
  43     return retc;
  44 }
  45
  46 int SerialHalfDuplex::_getc(void) {
  47     return Serial::_getc();
  48 }
  49
  50 } // End namespace
  51
  52 #endif