From 35f5cbaed433fc9217dd5c442e7c179e0e81c918 Mon Sep 17 00:00:00 2001 From: liminyang Date: Wed, 17 Jun 2020 11:58:41 +0800 Subject: [PATCH] docs:perfect 128-bit UUID description The previous description is not easy for the reader to understand, some changees have been made to perfect it. Closes https://github.com/espressif/esp-idf/issues/5057 --- .../Gatt_Client_Example_Walkthrough.md | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/examples/bluetooth/bluedroid/ble/gatt_client/tutorial/Gatt_Client_Example_Walkthrough.md b/examples/bluetooth/bluedroid/ble/gatt_client/tutorial/Gatt_Client_Example_Walkthrough.md index 8c82d34b15..26a639b8a0 100644 --- a/examples/bluetooth/bluedroid/ble/gatt_client/tutorial/Gatt_Client_Example_Walkthrough.md +++ b/examples/bluetooth/bluedroid/ble/gatt_client/tutorial/Gatt_Client_Example_Walkthrough.md @@ -484,6 +484,25 @@ Where, ```c #define REMOTE_SERVICE_UUID 0x00FF ``` +If UUID of the service application the user is interested in is 128-bit, then there is one note below for the user which is relevant with the little-endian storage mode of the processor architecture. +The struct of UUID is defined as: + +```c +typedef struct { +#define ESP_UUID_LEN_16 2 +#define ESP_UUID_LEN_32 4 +#define ESP_UUID_LEN_128 16 + uint16_t len; /*!< UUID length, 16bit, 32bit or 128bit */ + union { + uint16_t uuid16; /*!< 16bit UUID */ + uint32_t uuid32; /*!< 32bit UUID */ + uint8_t uuid128[ESP_UUID_LEN_128]; /*!< 128bit UUID */ + } uuid; /*!< UUID */ +} __attribute__((packed)) esp_bt_uuid_t; +``` + +Note: In little-endian storage mode, you can define service UUID directly in the normal order if it's a 16-bit or a 32-bit UUID, but if service UUID is 128-bit, there is minor difference. For example, if the UUID of the service application that the user is interested in is 12345678-a1b2-c3d4-e5f6-9fafd205e457, `REMOTE_SERVICE_UUID` should be defined as {0x57,0xE4,0x05,0xD2,0xAF,0x9F,0xF6,0xE5,0xD4,0xC3,0xB2,0xA1,0x78,0x56,0x34,0x12}. + The services are then discovered as follows: ```c