add examples

RTL00_SDKV35a/example_sources/gpio_pulse_measure/readme.txt

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+Example Description
+
+This example describes how to use GPIO read/write mbed api to generate a pulse and to measure the pulse width.
+
+Requirement Components:
+    a wire
+
+Pin name PC_4 and PC_5 map to GPIOC_4 and GPIOC_5:
+ - PC_4 as the interrupt GPIO pin with no pull (High-Z).
+ - PC_5 as output to generate a pulse.
+ - Use a wire to connect PC_4 and PC_5
+
+In this example, the UART consol will print out the measured width (in us) of the pulse which generated by PC_5.

RTL00_SDKV35a/example_sources/gpio_pulse_measure/src/main.c

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+/*
+ *  Routines to access hardware
+ *
+ *  Copyright (c) 2013 Realtek Semiconductor Corp.
+ *
+ *  This module is a confidential and proprietary property of RealTek and
+ *  possession or use of this module requires written permission of RealTek.
+ */
+
+#include "device.h"
+#include "gpio_api.h"   // mbed
+#include "gpio_irq_api.h"   // mbed
+#include "diag.h"
+#include "us_ticker_api.h"
+#include "main.h"
+
+#define GPIO_OUT_PIN        PC_5
+#define GPIO_IRQ_PIN        PC_4
+
+gpio_t gpio_out;
+gpio_irq_t gpio_irq;
+volatile char irq_rise;
+
+
+void gpio_demo_irq_handler (uint32_t id, gpio_irq_event event)
+{
+    static unsigned int rise_time;
+    static unsigned int fall_time;
+
+    if (irq_rise) {
+        rise_time = us_ticker_read();
+        // Changed as Falling Edge Trigger
+        gpio_irq_set_event(&gpio_irq, IRQ_FALL);
+        irq_rise = 0;
+    } else {
+        fall_time = us_ticker_read();
+        // Changed as Rising Edge Trigger
+        gpio_irq_set_event(&gpio_irq, IRQ_RISE);
+        irq_rise = 1;
+
+        DBG_8195A("%d\n", (fall_time-rise_time));
+    }
+}
+
+/**
+  * @brief  Main program.
+  * @param  None
+  * @retval None
+  */
+void main(void)
+{
+
+    // Init LED control pin
+    gpio_init(&gpio_out, GPIO_OUT_PIN);
+    gpio_dir(&gpio_out, PIN_OUTPUT);    // Direction: Output
+    gpio_mode(&gpio_out, PullNone);     // No pull
+    gpio_write(&gpio_out, 0);
+
+    // Initial Push Button pin as interrupt source
+    gpio_irq_init(&gpio_irq, GPIO_IRQ_PIN, gpio_demo_irq_handler, (uint32_t)(&gpio_irq));
+    gpio_irq_set(&gpio_irq, IRQ_RISE, 1);   // Falling Edge Trigger
+    irq_rise = 1;
+    gpio_irq_pull_ctrl(&gpio_irq, PullNone);
+    gpio_irq_enable(&gpio_irq);
+
+    while(1) {
+        wait_ms(500);
+        gpio_write(&gpio_out, 1);
+        wait_us(1000);
+        gpio_write(&gpio_out, 0);
+    }
+}
+