Squashed 'tmk_core/' changes from 7967731..b9e0ea0

b9e0ea0 Merge commit '7fa9d8bdea3773d1195b04d98fcf27cf48ddd81d' as 'tool/mbed/mbed-sdk'
7fa9d8b Squashed 'tool/mbed/mbed-sdk/' content from commit 7c21ce5

git-subtree-dir: tmk_core
git-subtree-split: b9e0ea08cb940de20b3610ecdda18e9d8cd7c552

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

@@ -0,0 +1,52 @@
+/* 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