This example demonstrates using the GattClient API to control BLE client devices. The canonical source for this example lives at https://github.com/ARMmbed/mbed-os-example-ble/tree/master/BLE_LEDBlinker

Revision:
75:1a8d19363522
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/source/pretty_printer.h	Mon Jan 14 10:45:54 2019 +0000
@@ -0,0 +1,95 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <mbed.h>
+#include "ble/BLE.h"
+
+inline void print_error(ble_error_t error, const char* msg)
+{
+    printf("%s: ", msg);
+    switch(error) {
+        case BLE_ERROR_NONE:
+            printf("BLE_ERROR_NONE: No error");
+            break;
+        case BLE_ERROR_BUFFER_OVERFLOW:
+            printf("BLE_ERROR_BUFFER_OVERFLOW: The requested action would cause a buffer overflow and has been aborted");
+            break;
+        case BLE_ERROR_NOT_IMPLEMENTED:
+            printf("BLE_ERROR_NOT_IMPLEMENTED: Requested a feature that isn't yet implement or isn't supported by the target HW");
+            break;
+        case BLE_ERROR_PARAM_OUT_OF_RANGE:
+            printf("BLE_ERROR_PARAM_OUT_OF_RANGE: One of the supplied parameters is outside the valid range");
+            break;
+        case BLE_ERROR_INVALID_PARAM:
+            printf("BLE_ERROR_INVALID_PARAM: One of the supplied parameters is invalid");
+            break;
+        case BLE_STACK_BUSY:
+            printf("BLE_STACK_BUSY: The stack is busy");
+            break;
+        case BLE_ERROR_INVALID_STATE:
+            printf("BLE_ERROR_INVALID_STATE: Invalid state");
+            break;
+        case BLE_ERROR_NO_MEM:
+            printf("BLE_ERROR_NO_MEM: Out of Memory");
+            break;
+        case BLE_ERROR_OPERATION_NOT_PERMITTED:
+            printf("BLE_ERROR_OPERATION_NOT_PERMITTED");
+            break;
+        case BLE_ERROR_INITIALIZATION_INCOMPLETE:
+            printf("BLE_ERROR_INITIALIZATION_INCOMPLETE");
+            break;
+        case BLE_ERROR_ALREADY_INITIALIZED:
+            printf("BLE_ERROR_ALREADY_INITIALIZED");
+            break;
+        case BLE_ERROR_UNSPECIFIED:
+            printf("BLE_ERROR_UNSPECIFIED: Unknown error");
+            break;
+        case BLE_ERROR_INTERNAL_STACK_FAILURE:
+            printf("BLE_ERROR_INTERNAL_STACK_FAILURE: internal stack faillure");
+            break;
+    }
+    printf("\r\n");
+}
+
+/** print device address to the terminal */
+void print_address(const uint8_t *addr)
+{
+    printf("%02x:%02x:%02x:%02x:%02x:%02x\r\n",
+           addr[5], addr[4], addr[3], addr[2], addr[1], addr[0]);
+}
+
+inline void print_mac_address()
+{
+    /* Print out device MAC address to the console*/
+    Gap::AddressType_t addr_type;
+    Gap::Address_t address;
+    BLE::Instance().gap().getAddress(&addr_type, address);
+    printf("DEVICE MAC ADDRESS: ");
+    print_address(address);
+}
+
+inline const char* phy_to_string(Gap::Phy_t phy) {
+    switch(phy.value()) {
+        case Gap::Phy_t::LE_1M:
+            return "LE 1M";
+        case Gap::Phy_t::LE_2M:
+            return "LE 2M";
+        case Gap::Phy_t::LE_CODED:
+            return "LE coded";
+        default:
+            return "invalid PHY";
+    }
+}