#74 Support SoftwareSerial library

 * Add a new API attachInterruptWithDebounce() that allows user to control debounce time setting
 * Revise `delayMicroseconds()` to use `hal_gpt` API instead.
 * Add new library `SoftwareSerial` that is modified from the Arduino SoftwareSerial library, replacing register writes to generic Arduino APIs, e.g. `digitalWrite`. LinkIt 7697 has a faster clock so the generic GPIO writes API is still fast enough for SoftwareSerial up to 115200 baud.

middleware/third_party/arduino/hardware/arduino/mt7697/cores/arduino/delay.c

@@ -2,6 +2,7 @@
 #include "variant_delay.h"
 #include "cmsis.h"
 #include "delay.h"
+#include <hal_gpt.h>
 
 
 // Get current timestamp, unit: ms
@@ -41,12 +42,12 @@ uint32_t micros( void )
 
 void delayMicroseconds(unsigned int us)
 {
-	uint32_t timeout_micros = micros() + us;
-
-	while(!time_after(micros(), timeout_micros)) ;
+	hal_gpt_delay_us(us);
 }
 
-void yield(void) {}
+void yield(void) {
+
+}
 
 void delay( uint32_t ms )
 {

middleware/third_party/arduino/hardware/arduino/mt7697/cores/arduino/pin_mux.c

@@ -5,6 +5,9 @@
 
 bool pin_has_eint(pin_desc_t *pin)
 {
+	if (NULL == pin)
+		return false;
+
 	if (pin->pin_info_eint_num >= HAL_EINT_NUMBER_MAX)
 		return false;
 

middleware/third_party/arduino/hardware/arduino/mt7697/cores/arduino/wiring_interrupt.c

@@ -15,7 +15,12 @@ static void default_hal_eint_callback(void *arduino_callback)
 		callback();
 }
 
-void attachInterrupt(uint32_t pin, voidFuncPtr callback, uint32_t mode)
+void attachInterrupt(uint32_t pin, voidFuncPtr callback, uint32_t mode) {
+	// by default we set the debounce time to 50 ms
+	return attachInterruptWithDebounce(pin, callback, mode, 50);
+}
+
+void attachInterruptWithDebounce(uint32_t pin, voidFuncPtr callback, uint32_t mode, uint32_t debounceTime)
 {
 	static hal_eint_trigger_mode_t mode_to_eint_trigger[] = {
 		[LOW]     = HAL_EINT_LEVEL_LOW,
@@ -41,8 +46,7 @@ void attachInterrupt(uint32_t pin, voidFuncPtr callback, uint32_t mode)
 		goto FAIL;
 
 	eint_config.trigger_mode  = mode_to_eint_trigger[mode];
-	eint_config.debounce_time = 50; // debounce time unit: ms
-
+	eint_config.debounce_time = debounceTime; // debounce time unit: ms
 
 	ret = hal_eint_init(pin_get_eint_num(pin_desc), &eint_config);
 

middleware/third_party/arduino/hardware/arduino/mt7697/cores/arduino/wiring_interrupt.h

@@ -9,6 +9,7 @@ extern "C" {
 typedef void (*voidFuncPtr)(void) ;
 
 extern void attachInterrupt(uint32_t pin, voidFuncPtr callback, uint32_t mode);
+extern void attachInterruptWithDebounce(uint32_t pin, voidFuncPtr callback, uint32_t mode, uint32_t debounceTime);
 extern void detachInterrupt(uint32_t pin);
 
 extern void interrupts(void);

middleware/third_party/arduino/hardware/arduino/mt7697/libraries/SoftwareSerial/examples/SoftwareSerialExample/SoftwareSerialExample.ino

@@ -0,0 +1,57 @@
+/*
+  Software serial multple serial test
+
+ Receives from the hardware serial, sends to software serial.
+ Receives from software serial, sends to hardware serial.
+
+ The circuit:
+ * RX is digital pin 2  (connect to TX of other device)
+ * TX is digital pin 11 (connect to RX of other device)
+
+
+ Note:
+ Not all pins on LinkIt 7697 support change interrupts,
+ so only the following can be used for RX:
+ 2, 3
+
+ created back in the mists of time
+ modified 25 May 2012
+ by Tom Igoe
+ based on Mikal Hart's example
+
+ modified Dec 2017
+ by MediaTek Labs
+
+ This example code is in the public domain.
+
+ */
+#include <SoftwareSerial.h>
+
+// On LinkIt 7697, the RX pin must be one of the EINT pins, such as P2 and P3.
+// There are no limitations on TX pin.
+SoftwareSerial mySerial(2, 11); // RX, TX
+
+void setup() {
+  // Open serial communications and wait for port to open:
+  Serial.begin(9600);
+  while (!Serial) {
+    ; // wait for serial port to connect. Needed for native USB port only
+  }
+
+
+  Serial.println("Goodnight moon!");
+
+  // set the data rate for the SoftwareSerial port
+  mySerial.begin(4800);
+  mySerial.println("Hello, world?");
+}
+
+void loop() { // run over and over
+  if (mySerial.available()) {
+    Serial.write(mySerial.read());
+  }
+  if (Serial.available()) {
+    mySerial.write(Serial.read());
+  }
+}
+

middleware/third_party/arduino/hardware/arduino/mt7697/libraries/SoftwareSerial/examples/TwoPortReceive/TwoPortReceive.ino

@@ -0,0 +1,90 @@
+/*
+  Software serial multple serial test
+
+ Receives from the two software serial ports,
+ sends to the hardware serial port.
+
+ In order to listen on a software port, you call port.listen().
+ When using two software serial ports, you have to switch ports
+ by listen()ing on each one in turn. Pick a logical time to switch
+ ports, like the end of an expected transmission, or when the
+ buffer is empty. This example switches ports when there is nothing
+ more to read from a port
+
+ The circuit:
+ Two devices which communicate serially are needed.
+ * First serial device's TX attached to digital pin 2(RX), RX to pin 11(TX)
+ * Second serial device's TX attached to digital pin 3(RX), RX to pin 9(TX)
+
+ Note:
+ Not all pins on LinkIt 7697 support change interrupts,
+ so only the following can be used for RX:
+ 2, 3
+
+ created 18 Apr. 2011
+ modified 19 March 2016
+ by Tom Igoe
+ based on Mikal Hart's twoPortRXExample
+
+ modified Dec 2017
+ by MediaTek Labs
+
+ This example code is in the public domain.
+
+ */
+
+#include <SoftwareSerial.h>
+
+// software serial #1: RX = digital pin 2, TX = digital pin 11
+SoftwareSerial portOne(2, 11);
+
+// software serial #2: RX = digital pin 3, TX = digital pin 9
+SoftwareSerial portTwo(3, 9);
+
+void setup() {
+  // Open serial communications and wait for port to open:
+  Serial.begin(9600);
+  while (!Serial) {
+    ; // wait for serial port to connect. Needed for native USB port only
+  }
+
+
+  // Start each software serial port
+  portOne.begin(9600);
+  portTwo.begin(9600);
+}
+
+void loop() {
+  // By default, the last intialized port is listening.
+  // when you want to listen on a port, explicitly select it:
+  portOne.listen();
+  Serial.println("Data from port one:");
+  // while there is data coming in, read it
+  // and send to the hardware serial port:
+  while (portOne.available() > 0) {
+    char inByte = portOne.read();
+    Serial.write(inByte);
+  }
+
+  // blank line to separate data from the two ports:
+  Serial.println();
+
+  // Now listen on the second port
+  portTwo.listen();
+  // while there is data coming in, read it
+  // and send to the hardware serial port:
+  Serial.println("Data from port two:");
+  while (portTwo.available() > 0) {
+    char inByte = portTwo.read();
+    Serial.write(inByte);
+  }
+
+  // blank line to separate data from the two ports:
+  Serial.println();
+}
+
+
+
+
+
+

middleware/third_party/arduino/hardware/arduino/mt7697/libraries/SoftwareSerial/keywords.txt

@@ -0,0 +1,30 @@
+#######################################
+# Syntax Coloring Map for SoftwareSerial
+# (formerly NewSoftSerial)
+#######################################
+
+#######################################
+# Datatypes (KEYWORD1)
+#######################################
+
+SoftwareSerial	KEYWORD1
+
+#######################################
+# Methods and Functions (KEYWORD2)
+#######################################
+
+begin	KEYWORD2
+end	KEYWORD2
+read	KEYWORD2
+write	KEYWORD2
+available	KEYWORD2
+isListening	KEYWORD2
+overflow	KEYWORD2
+flush	KEYWORD2
+listen	KEYWORD2
+peek	KEYWORD2
+
+#######################################
+# Constants (LITERAL1)
+#######################################
+

middleware/third_party/arduino/hardware/arduino/mt7697/libraries/SoftwareSerial/library.properties

@@ -0,0 +1,10 @@
+name=SoftwareSerial
+version=0.1
+author=MediaTek Labs
+maintainer=MediaTek Labs <http://labs.mediatek.com>
+sentence=Enables serial communication on EINT pins.
+paragraph=The SoftwareSerial library has been developed to allow serial (UART) transmission(TX) on any pin, and receiving(RX) on EINT pins such as P2 and P3 on LinkIt 7697 HDK.
+category=Communication
+url=https://github.com/MediaTek-Labs/Arduino-Add-On-for-LinkIt-SDK
+architectures=linkit_rtos
+