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/* mbed Microcontroller Library - SerialHalfDuplex
* Copyright (c) 2010-2011 ARM Limited. All rights reserved.
*/
#include "SerialHalfDuplex.h"
#if DEVICE_SERIAL
#include "pinmap.h"
#include "serial_api.h"
namespace mbed {
SerialHalfDuplex::SerialHalfDuplex(PinName tx, PinName rx)
: Serial(tx, rx) {
gpio_init(&gpio, tx, PIN_INPUT);
gpio_mode(&gpio, PullNone); // no pull
}
// To transmit a byte in half duplex mode:
// 1. Disable interrupts, so we don't trigger on loopback byte
// 2. Set tx pin to UART out
// 3. Transmit byte as normal
// 4. Read back byte from looped back tx pin - this both confirms that the
// transmit has occurred, and also clears the byte from the buffer.
// 5. Return pin to input mode
// 6. Re-enable interrupts
int SerialHalfDuplex::_putc(int c) {
int retc;
// TODO: We should not disable all interrupts
__disable_irq();
serial_pinout_tx(gpio.pin);
Serial::_putc(c);
retc = Serial::getc(); // reading also clears any interrupt
pin_function(gpio.pin, 0);
__enable_irq();
return retc;
}
int SerialHalfDuplex::_getc(void) {
return Serial::_getc();
}
} // End namespace
#endif
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