Diff: SerialHalfDuplex.cpp

Revision:

1:946c65496383

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SerialHalfDuplex.cpp	Tue Apr 26 16:46:51 2016 +0000
@@ -0,0 +1,76 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2012 ARM Limited
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * NOTE: This is an unsupported legacy untested library.
+ */
+#include "SerialHalfDuplex.h"
+ 
+#if DEVICE_SERIAL
+#include "mbed.h"
+#include "pinmap.h"
+#include "serial_api.h"
+#include "gpio_api.h"
+ 
+namespace mbed {
+ 
+SerialHalfDuplex::SerialHalfDuplex(PinName tx, PinName rx, const char *name)
+    : Serial(tx, rx, name) {
+    _txpin = tx;
+    
+    DigitalIn TXPIN(_txpin);         // set as input 
+    pin_mode(_txpin, PullNone); // no pull
+    pin_function(_txpin, 0);    // set as gpio
+}
+ 
+// 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(_txpin);
+    
+    Serial::_putc(c);
+    retc = Serial::getc();       // reading also clears any interrupt
+    
+    pin_function(_txpin, 0);
+    
+    __enable_irq();
+    
+    return retc;
+}
+ 
+int SerialHalfDuplex::_getc(void) {
+    return Serial::_getc();
+}
+ 
+} // End namespace
+ 
+#endif
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