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