feat(ble): Adds Characteristic User Description

Adds Descriptor 0x2901

This is the Characteristic User Description, commomnly used in BLE. Adds the implementation for make it easier to be used.

Author: SuGlider

libraries/BLE/src/BLE2901.cpp

@@ -0,0 +1,41 @@
+/*
+   BLE2901.h
+ 
+     GATT Descriptor 0x2901 Characteristic User Description
+
+     The value of this description is a user-readable string
+     describing the characteristic.
+
+     The Characteristic User Description descriptor
+     provides a textual user description for a characteristic
+     value.
+     If the Writable Auxiliary bit of the Characteristics
+     Properties is set then this descriptor is written. Only one
+     User Description descriptor exists in a characteristic
+     definition.
+*/
+
+#include "soc/soc_caps.h"
+#if SOC_BLE_SUPPORTED
+
+#include "sdkconfig.h"
+#if defined(CONFIG_BLUEDROID_ENABLED)
+
+#include "BLE2901.h"
+
+BLE2901::BLE2901() : BLEDescriptor(BLEUUID((uint16_t)0x2901)) {
+}  // BLE2901
+
+/**
+ * @brief Set the Characteristic User Description
+ */
+void BLE2901::setDescription(String userDesc) {
+  if (userDesc.length() > ESP_GATT_MAX_ATTR_LEN) {
+    log_e("Size %d too large, must be no bigger than %d", userDesc.length(), ESP_GATT_MAX_ATTR_LEN);
+    return;    
+  }
+  setValue(userDesc);
+}
+
+#endif
+#endif /* SOC_BLE_SUPPORTED */