Lee Kai Xuan / mbed-os

mbed-os

Fork of mbed-os by erkin yucel

features/unsupported/tests/libs/SerialHalfDuplex/SerialHalfDuplex.cpp@1:3deb71413561, 2017-07-20 (annotated)

Committer:
xuaner
Date:
Thu Jul 20 14:26:57 2017 +0000
Revision:
1:3deb71413561
Parent:
0:f269e3021894 
mbed_os

Who changed what in which revision?

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elessair 0:f269e3021894 1 /* mbed Microcontroller Library - SerialHalfDuplex
elessair 0:f269e3021894 2 * Copyright (c) 2010-2011 ARM Limited. All rights reserved.
elessair 0:f269e3021894 3 */
elessair 0:f269e3021894 4 #include "SerialHalfDuplex.h"
elessair 0:f269e3021894 5 #include "critical.h"
elessair 0:f269e3021894 6
elessair 0:f269e3021894 7 #if DEVICE_SERIAL
elessair 0:f269e3021894 8
elessair 0:f269e3021894 9 #include "pinmap.h"
elessair 0:f269e3021894 10 #include "serial_api.h"
elessair 0:f269e3021894 11
elessair 0:f269e3021894 12 namespace mbed {
elessair 0:f269e3021894 13
elessair 0:f269e3021894 14 SerialHalfDuplex::SerialHalfDuplex(PinName tx, PinName rx)
elessair 0:f269e3021894 15 : Serial(tx, rx) {
elessair 0:f269e3021894 16
elessair 0:f269e3021894 17 gpio_init(&gpio, tx, PIN_INPUT);
elessair 0:f269e3021894 18 gpio_mode(&gpio, PullNone); // no pull
elessair 0:f269e3021894 19 }
elessair 0:f269e3021894 20
elessair 0:f269e3021894 21 // To transmit a byte in half duplex mode:
elessair 0:f269e3021894 22 // 1. Disable interrupts, so we don't trigger on loopback byte
elessair 0:f269e3021894 23 // 2. Set tx pin to UART out
elessair 0:f269e3021894 24 // 3. Transmit byte as normal
elessair 0:f269e3021894 25 // 4. Read back byte from looped back tx pin - this both confirms that the
elessair 0:f269e3021894 26 // transmit has occurred, and also clears the byte from the buffer.
elessair 0:f269e3021894 27 // 5. Return pin to input mode
elessair 0:f269e3021894 28 // 6. Re-enable interrupts
elessair 0:f269e3021894 29 int SerialHalfDuplex::_putc(int c) {
elessair 0:f269e3021894 30 int retc;
elessair 0:f269e3021894 31
elessair 0:f269e3021894 32 // TODO: We should not disable all interrupts
elessair 0:f269e3021894 33 core_util_critical_section_enter();
elessair 0:f269e3021894 34
elessair 0:f269e3021894 35 serial_pinout_tx(gpio.pin);
elessair 0:f269e3021894 36
elessair 0:f269e3021894 37 Serial::_putc(c);
elessair 0:f269e3021894 38 retc = Serial::getc(); // reading also clears any interrupt
elessair 0:f269e3021894 39
elessair 0:f269e3021894 40 pin_function(gpio.pin, 0);
elessair 0:f269e3021894 41
elessair 0:f269e3021894 42 core_util_critical_section_exit();
elessair 0:f269e3021894 43
elessair 0:f269e3021894 44 return retc;
elessair 0:f269e3021894 45 }
elessair 0:f269e3021894 46
elessair 0:f269e3021894 47 int SerialHalfDuplex::_getc(void) {
elessair 0:f269e3021894 48 return Serial::_getc();
elessair 0:f269e3021894 49 }
elessair 0:f269e3021894 50
elessair 0:f269e3021894 51 } // End namespace
elessair 0:f269e3021894 52
elessair 0:f269e3021894 53 #endif