Add more snippets (#109)

* add more example snippets

* deprecate wait function

Author: Qinghao Shi

APIs_Drivers/Watchdog_ex_1/main.cpp

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2020 Arm Limited and affiliates.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "mbed.h"
+
+const uint32_t TIMEOUT_MS = 5000;
+InterruptIn button(BUTTON1);
+volatile int countdown = 9;
+
+void trigger()
+{
+    Watchdog::get_instance().kick();
+    countdown = 9;
+}
+
+int main()
+{
+    printf("\r\nTarget started.\r\n");
+
+    Watchdog &watchdog = Watchdog::get_instance();
+    watchdog.start(TIMEOUT_MS);
+    button.rise(&trigger);
+
+    uint32_t watchdog_timeout = watchdog.get_timeout();
+    printf("Watchdog initialized to %lu ms.\r\n", watchdog_timeout);
+    printf("Press BUTTON1 at least once every %lu ms to kick the "
+           "watchdog and prevent system reset.\r\n", watchdog_timeout);
+
+    while (1) {
+        printf("\r%3i", countdown--);
+        fflush(stdout);
+        ThisThread::sleep_for(TIMEOUT_MS / 10);
+    }
+}

APIs_NetworkInterface/Mesh_Ex1/main.cpp

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2020 Arm Limited and affiliates.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "mbed.h"
+
+int main(void)
+{
+    MeshInterface *mesh = MeshInterface::get_default_instance();
+
+    int status = mesh->connect();
+    if (status) {
+        printf("Connection failed! error %d\n", status);
+        return status;
+    }
+
+    printf("Connected!\n");
+
+    UDPSocket sock;
+    status = sock.open(mesh);
+    if (status) {
+        printf("Failed to open socket, error %d\n", status);
+    }
+
+    // Now the interface is connected, and I can communicate with Sockets
+}

Tutorials_UsingAPIs/TLS_Communication/main.cpp

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2020 Arm Limited and affiliates.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "mbed.h"
+#include "mbed_trace.h"
+
+const char cert[] = /* your certificate, see above */ "";
+
+int main(void)
+{
+
+    nsapi_size_or_error_t result;
+    NetworkInterface *net = NetworkInterface::get_default_instance();
+
+    if (!net) {
+        printf("Error! No network inteface found.\n");
+        return 0;
+    }
+
+    printf("Connecting to network\n");
+    result = net->connect();
+    if (result != 0) {
+        printf("Error! net->connect() returned: %d\n", result);
+        return result;
+    }
+
+    TLSSocket *socket = new TLSSocket;
+    result = socket->set_root_ca_cert(cert);
+    if (result != 0) {
+        printf("Error: socket->set_root_ca_cert() returned %d\n", result);
+        return result;
+    }
+
+    result = socket->open(net);
+    if (result != 0) {
+        printf("Error! socket->open() returned: %d\n", result);
+        return result;
+    }
+
+    printf("Connecting to os.mbed.com\n");
+    result = socket->connect(SocketAddress("os.mbed.com", 443));
+    if (result != 0) {
+        printf("Error! socket->connect() returned: %d\n", result);
+        return result;
+    }
+}