Ble services and characteristics

Ble services and characteristics. Send all values written to the O3 as strings in byte array format. public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {. When two BLE devices interact, one acts as a Peripheral, offering GATT Services, and the other acts as a Central, consuming Jan 10, 2024 · Characteristics are arranged into services. Nov 17, 2023 · BLE service discovery is a crucial step in BLE communication, where a central device (the Flutter app in our case) discovers the services and characteristics offered by a peripheral device. Unlike Bluetooth that is always on, BLE remains in sleep mode constantly except for when a connection is initiated. Apr 17, 2024 · An entry point to the BLE device’s GATT profile. Actually Firmware device already set up Services and Characteristics also. Characteristics are the actual logical input and output nodes. A service is a grouping of one or more attributes, some of which are characteristics. It is worth noting that BLE profiles don’t Jul 21, 2015 · Link Loss - set the Alert Level characteristic of a BLE Device (readValue & writeValue). Jun 23, 2018 · I'm trying to connect to my bluetooth device, however upon connecting and discovering all services and characteristics, I'm unable to advance because the information returned is insufficient. It is a pretty good device that supports BLE version 4. Recall that services and characteristics are registered with NimBLE via attribute tables. Read the Bluetooth Core Specification v4. The attributes in a GATT server are grouped into services, each of which can contain zero or more characteristics. It BLE Services. Automatic Reconnect - reconnect to a disconnected BLE device using an exponential backoff algorithm. I`d like to add my custom characteristic. It can scan for BLE devices showing device information and advert payload as well as connect to devices and access GATT services/characteristics. Understanding these events is imperative for any BLE developer, and there are two aspects to achieving this: Learn the concepts in theory. Data is passed and stored in the form of characteristics which are stored in memory on the Bluetooth low Jan 9, 2024 · BLE connectivity involves several key concepts, including GATT (Generic Attribute Profile), services, characteristics, and descriptors. PPG Heart rate sensor. May 27, 2021 · Even if i change CFG_BLE_NUM_GATT_SERVICES to 10 the configuration tool doesn't allow me to put a higher number than 5 for the "number of services". Once the services are discovered I am catching it in. It defines how ATT attributes are grouped together into sets to form services. Next, go to “Tools” > “Board” > “Boards Manager”. Part 2 – ESP32 BLE client. Communications with the phone are done via BLE 5. There are two types: 16-bit (short) UUIDs for well-known BLE services. "Parameter of services; maximum is 5" Jonas Generic Attribute Profile (GATT) Operations. Apr 10, 2023 · BLE Services and Characteristics Services. As shown in the below figure, attributes are the main building blocks for services. I have trubble location BLE service, etc in the code/repository. This is for transmitting audio captured on the board to my mobile device, is it possible? or is it possible to create a May 8, 2019 · I have suddenly started getting GattCommunicationStatus. 128-bit (long) UUIDs for everything else. Attributes forming a service with two characteristics. 1 day ago · Answers checklist. A GATT service comprises a collection of logically related data called characteristics. GATT operates using Services and Characteristics. Aug 13, 2020 · Modbus is one of those protocols. It has all the services and profiles listed by SIG. You can define your own services, or use standard services (see section 3. There used to be a page with links to PDF and XML files for each Dec 27, 2021 · Bluetooth offers continuous communication in two directions. The 16-bit service IDs are assigned by the Bluetooth SIG and are listed here. You can start with the following tutorial: Getting Started with ESP32 Bluetooth Low Energy (BLE) on Arduino IDE Oct 19, 2016 · These reserved UUIDs cannot be used for any custom services or characteristics, so you need to avoid them. Intro to Bluetooth Generic Attribute Profile (GATT) Ellisys. May 23, 2018 · Yes, Bluetooth SIG is the best place to look for all the services and profiles available till date. Apr 12, 2023 · This example demonstrates how a GATT Client can discover services, characteristics and descriptors on a GATT server Database device with PSoC4 BLE Device. Characteristics. 0 and higher: Maximum number of services: 10; Maximum number of characteristics: 30 Feb 19, 2023 · The hierarchical structure consists of profiles, services, and characteristics. This bracelet gives you lot of health information . Unfortunately, I realized that in order to do so, it is necessary to define available services and supporting characteristics on the Arduino for the BLE module, before I can start using it. Thingy modules - Layer containing high level functionality and features. - eriklins/InsideBlue-BLE-Tool Jun 23, 2018 · I'm trying to connect to my bluetooth device, however upon connecting and discovering all services and characteristics, I'm unable to advance because the information returned is insufficient. May 1, 2015 · The commands below have the following limitations due to SRAM and resource availability, which should be kept in mind when creating or working with customer GATT services and characteristics. I receive no service UUIDs nor any characteristic UUIDs. A BLE device can scan to discover another BLE device that is advertising and initiate an outgoing connection to it. I want to be able to communicate with this through a Xamarin forms application. All attributes are defined inside a table and they have a handle, a type (with a UUID), a value (and permissions). GATT is a standardized protocol that defines how data is transferred between BLE devices. In the following example, once the service successfully connects to the device (indicated by the Dec 3, 2019 · BLE allows devices to communicate for years on a coin cell battery. I used Advertising, Services, Characteristics and Timer tutorials on Nordic DevZone. Depending on the design implementation, a BLE device can support either one or both of the roles. Feb 26, 2024 · In BLE, devices communicate through a client-server architecture, where one device acts as the central (client) and the other as the peripheral (server). Services, Characteristics, and Descriptors. First I tried with the latest version. Bluetooth is voice capable and BLE is not. Generic Access Profile (GAP) It defines procedures for how a BLE device can communicate with others through broadcasting or connecting. If you want to get started with BLE immediately, try my Blessed library for Android. i("onConnectionStateChange", "Status: " + status); switch (newState) {. This makes it consume very low power. What do I need to do to be able to access the UUIDs to then be able to read from the characteristics? Normally to recognize the custom services and characteristics, you can use the Characteristic User descriptor for that characteristic in a service. Feb 7, 2018 · BLE and Android, the more characteristics and services the more slowly. 128-bit UUID = 16-bit Attribute UUID * 2^96 + Bluetooth_Base_UUID with Bluetooth_Base_UUID being 00000000-0000-1000-8000-00805F9B34FB. Generic Attribute Profile (GATT) Just as the GAP layer handles most connection-related functionality, the GATT layer of the Bluetooth low energy protocol stack is used by the application for data communication between two connected devices. The GATT protocol defines services, characteristics, and descriptors and each of Similar to Services, each Characteristic distinguishes itself via a pre-defined 16-bit or 128-bit UUID. getServices() Returns a list of GATT services offered by the remote device. I assume it does not exist in the code since it is addad dynamicly but i am not finding some kind of CSV file or simular holding data for this. This We would like to show you a description here but the site won’t allow us. Following problem: I’m working on a project with android (5. A Service is a collection of data and associated behaviors to accomplish a particular function or feature of a device. 0 (newer boards support higher version of BLE as well). Responsible for handling persistent storage of configuration and the default configuration. Those data items are in fact called Characteristics. These values apply to firmware 0. BLE only communicates in short bursts, and some BLE connections only go in one direction. Thingy application; BLE services Jun 26, 2020 · As with services, officially adopted BLE characteristics have 16-bit UUIDs and you can create your own with a 128-bit UUID. Services are predefined collections of characteristics that provide specific functionality. May 6, 2021 · For background, all BLE services and characteristics have universally unique identifiers (UUIDs). Each service contains a collection of characteristics Feb 17, 2020 · To interact with Bluetooth characteristics (read/write/notify) one must first discover what characteristics are available (even if you know what you are connecting to and what properties it has, the BLE stack underneath does not). I have implemented BLE central in my app. , this approach would quickly get pretty messy and cumbersome. So, to create a UUID for your custom services and characteristics you would: Jan 4, 2021 · BLE Services and Characteristics: The Generic Attribute Profile (GATT) To implement Bluetooth communication with BLE devices, we first need some understanding of the basic protocol underneath Nov 27, 2023 · Our BLE connectivity architecture process begins with establishing an in-depth understanding of the product. Services are identified by unique numbers known as UUIDs. When the value is updated any connected devices get a notification. Bluetooth profiles are implemented using a hierarchical structure: Services: A collection of GATT entries, grouping together attributes that are related to each other. Our deep knowledge of the connected product landscape. These characteristics, in turn, can include zero or more descriptors. The other two are battery related, and could be applicable to any kind of device. This knowledge generally comes from three areas: Conversations with client stakeholders. Mar 8, 2024 · A service can have one or more characteristics, and each service distinguishes itself from other services by means of a unique numeric ID called a UUID, which can be either 16-bit (for officially adopted BLE Services) or 128-bit (for custom services). Related characteristics are organized into a service. Nov 20, 2017 · 0. GATT provides a framework for all profiles defined either by the Bluetooth SIG or by the user. Bluetooth Low Energy ( Bluetooth LE, colloquially BLE, formerly marketed as Bluetooth Smart [1]) is a wireless personal area network technology designed and marketed by the Bluetooth Special Interest Group (Bluetooth SIG) [2] aimed at novel applications in the healthcare, fitness, beacons, [3] security, and home entertainment industries. UUIDs are no more than identifiers, 128-bit identifiers. a hardware feature) of a device like the buttons or a particular sensor. Discover Services & Characteristics - discover all accessible primary services and their characteristics from a BLE Device. This service grouping contains characteristics related to management tasks for the O3. Characteristics: Data containers. Jun 9, 2023 · This section lists the GATT services, characteristics, and their associated vendor UUIDs on the GATT server. To do so one must call: Feb 15, 2018 · IPWorks BLE contains a single component, BLEClient, which provides straightforward access to Bluetooth Low Energy (or BLE) operations. The ATT is made up of Services, Characteristics, and Descriptors. Each service can contain one or more characteristics and possesses its own unique numeric identifier, or UUID, which can be either 16 bits (for officially adopted BLE Services) or 128 bits (for custom services). Though our example device is a heart rate monitor, only two of the characteristics above are actually related to heart rate monitoring. idk what you are doing wrong. Services and characteristics are typically identified by their UUID. BLE is strictly cross-platform Xamarin Forms abstraction layer on top of BLE protocols. The BLEClient component makes it easy to work with services, characteristics, and descriptors exposed by GATT servers on remote BLE devices. 4 in the Assigned Numbers document). Bluetooth connections have a latency of up to 100ms. A service definition (commonly referred to as a service) is comprised of multiple attributes arranged in a GATT-specified format which facilitates standardized data exchange between Bluetooth LE devices. Apr 1, 2023 · Objective: This example demonstrates how a GATT Client can discover services, characteristics and descriptors on a GATT server Database device with PSoC6 BLE Device. Often a Service represents a particular feature (e. Bluetooth Nov 4, 2015 · While app from Play store can discover Services and Characteristics inside firmware device, my android application can not discover them, it always return empty services list. Any BLE device which has officially Feb 6, 2024 · Clarefy how to view BLE services,characteristics and descriptors added dynamicly to see input parameters. I'm developing a BLE Android App and have to choose the best service. Jan 3, 2024 · The first thing to do once you connect to the GATT Server on the BLE device is to perform service discovery. After getting services, As discussed earlier, each service has some characteristics. As of hardware, I have worked on PSoC4 BLE by Cypress Semiconductors. Plugin. So I have been trying with few different ways of defining services and characteristics using this long string as well as with BLEUUID() function as follows #define SERVICE_UUID BLEUUID((uint16_t)0x180D) #define CHARACTERISTIC_UUID BLEUUID((uint16_t)0x2A37) BLEDescriptor heartRateDescriptor(BLEUUID((uint16_t)0x2901)); Following is the sketch where I Oct 25, 2022 · Bluetooth Profiles. BLE specification defines two roles for a BLE device: Central and Peripheral. Every embedded device we worked on needed the same basic tests—ensure all the intended BLE components (services, characteristics) were there, were set up correctly, and that we could successfully communicate with them. A GATT service is a collection of conceptually related data called characteristics. For example HRM sensor data from health bands etc. Philips Hue BLE Services and Characteristics (WIP) - gist:f7907fdf6b470200702e75a30135caf3 Mar 30, 2020 · A Deep Dive into BLE Packets and Events. This video goes over the basics of the Generic Attribute Profile, the Attribute Profile (ATT), Services and Characteristics, Profiles and Data operations on the data exposed by devices. </p> <p>Where in project should i place this charecteristic`s fields description (data structures): PACKSTRUCT()? </p> <p>Another question is what gecko_evt is responsible for data reception on my device? Feb 3, 2023 · I am using ESP32-S3 board Lilygo T-Display. It exposes a human readable string to the connected device which can be used to recognize the characteristic. BLE’s primary application is short distance transmission of small amounts of data (low bandwidth). Resource Details. A Service is a container for logically related Bluetooth ® data items. This tutorial will show you how to create a custom service with a custom value characteristic in the ble_app_template project found in the Nordic nRF5 SDK v15. The idea was to have two similar characteristics within one service with uuids as GATTS_CHAR_UUID and GATTS_CHAR_UUID2. Initially, device will scan and connect to the peer device which is advertising with desirable May 10, 2020 · The battery level service contains one BLE read-only characteristic that is programmatically updated. So, characteristics are arranged into services; this groups them into related areas. , appetizers, entrees, desserts). g. [4] Nov 11, 2021 · The ESP32 client connects to the BLE server and it is notified of its temperature and humidity characteristic values. Once the board definitions are installed, you need to select the appropriate board from the “Tools” > “Board” menu. A full list of officially adopted BLE services can be seen on the Services (https:// Aug 10, 2016 · Services. A Bluetooth Profile is a specification describing a particular use case of Bluetooth-based wireless communication between devices. This provides information about the services available on the remote device as well as the service characteristics and their descriptors. share some code if its possible. Services. characteristicsForService() Method: Syntax: device. 3, Part G for more information. By using, 1. Overview: In this example project, BLE component is configured in GAP Central role. A Service can be thought of as the owner of the Characteristics inside it. UInt8. The services are the different sections of the menu (e. One given 128-bit value designates one given thing. Jul 27, 2020 · As with any new technology, rapid prototyping was the name of the game, and we needed to bring all of our cards to the table. It allows us to perform service discovery and connection teardown, request MTU updates (more on this later), and get access to the services and characteristics that are present on the BLE device. What do I need to do to be able to access the UUIDs to then be able to read from the characteristics? The commands below have the following limitations due to SRAM and resource availability, which should be kept in mind when creating or working with customer GATT services and characteristics. I tried with the ESP32-WROOM and ESP32C3-MINI. I compiled and flash the project successfully, but I couldn't get the BLE services to start. We can think of this as a handle to an established BLE connection. If you want to communicate with ModBus packages you just need to convert these packages to bytearray and sand it via predefined Services/Characteristics on BLE layer. More on that later. Each characteristic definition in an attribute table contains an access_cb field. 12 library which I've renamed to BlePeripheral2Enhanced V1. To achieve this efficiency, a client server architecture, named the Attribute Protocol (ATT) was adapted. The 16-bit UUIDs are shortcuts for a corresponding 128-bit UUID and is translated as. In the search bar, type “esp32” and click on the “esp32” entry that appears. SIG Member. Other types of Aug 26, 2015 · This structure defines basic elements such as services and characteristics, used in a profile. The 16-bit characteristic IDs are listed here. I've added the following features to the original BlePeripheral2 V1. They also want to send data back to the BLE peripheral since you’re also ready to write to characteristics. Controlls both the sensor drivers and the corresponding BLE services. Here is a breakdown of key concepts and operations in BLE: 1. Existing documentation and design schematics. So, we need to get these characteristics for a particular service. I guess it could be a bug of the tool as in the information box of "Number of characteristics", that seems to depend on that maximum number of services, too. You know about UUIDs from other contexts. This tutorial can be seen as the combined version of the BLE Advertising / Services / Characteristics , A Beginner's Tutorial series, which I strongly recommend to take a look at as they go deeper into the matter than this tutorial Feb 8, 2024 · I need to connect my seeedstudio nrf52840 to my mobile device and transfer data to it , without applications like Lightblue etc. This ESP32 is connected to an OLED display and it prints the latest readings. It’s meant to group together related attributes that satisfy a specific functionality on the server. Feb 1, 2020 · In Bluetooth, attributes types, GATT service types, characteristic types and descriptor types, and other constants are identified through UUIDs. 2 , Vol. Apr 15, 2019 · Now that we covered reading and writing characteristics, we will go in-depth on bonding in the next article. Steps : Once the device is connected I am making a call to discover services. BLE achieves this by focusing on sending small chunks of data as efficiently as possible. I have read the documentation ESP-IDF Programming Guide and the issue is not addressed there. Create a custom primary service with your own unique UUID. @Override. Note: you can actually purchase and reserve a 16-bit alias from the Bluetooth SIG here for a fee of $3,000, which would allow you to use the alias instead. For example, the device name should always be at UUID 00002A00-0000-1000-8000-00805F9B34FB. Log. To make sure that the issue is not in my main application, I created a simple test application based on the UWP Bluetooth system running in Console Application. Data is exchanged using the Generic Attribute Profile (GATT). Jun 29, 2022 · A service can have one or more characteristics, and each service distinguishes itself from other services by means of a unique numeric ID called a UUID, which can be either 16-bit (for officially adopted BLE Services) or 128-bit (for custom services). Think of BLE communication like a restaurant menu. after that you can go through the services to get the characteristics of each service. Nov 20, 2019 · The BLE standard provides the ATT protocol that defines the concept of attributes. A collection of characteristics is called a service. ble_lbs_on_ble_evt() is the dispatch function for the LED Button Service, and it is responsible for handling all BLE events related to this Dec 17, 2023 · Using this library, you can create your own custom BLE GATT Service or emulate manufacturer hardware if you know the service UUID and characteristics UUIDs. I have updated my IDF branch (master or release) to the latest version and checked that the issue is present there. 5. のAliexpressでBLE-9002 Digital Temp H2 Hydrogen-rich Meter 0-2990ppb Auto-Calibration BlueTooth APP Monitor Drinking Water Quality Tester Toolを購入します。 Lesson – BLE profiles, services, characteristics, device roles and network topology – Embedded Centric Jan 18, 2019 · Hello! I`m triing to make it clear for me: I`m using soc-temperature example for BGM13P. You can understand characteristics as containers for user data. Each service can have one or more characteristics and has its own unique numeric identifier, or UUID, which is either 16 bits (for officially adopted BLE Services) or 128 bits (for custom services). Given its low energy consumption and well-developed profiles, such as GATT, BLE is an ideal short-range wireless protocol for Internet of Things (IoT) devices, when compared to competing Aug 14, 2018 · I have an Arduino Uno connected to an HM-10 BLE device. The BLE API of the Moddable SDK The Moddable SDK does not have distinct classes in its BLE API for the roles defined by GAP and for GATT. 0. Oct 11, 2018 · Characteristics contain a single data point and akin to services, each characteristic has a unique ID or UUID that distinguishes itself from the other characteristic. How do I connect it with the inbuilt Bluetooth application in mobile devices, Are there any libraries or GitHub repos, or how can I achieve this?. Mar 16, 2020 · Setting up Xcode for BLE development; Bluetooth permissions; Scanning for BLE peripherals; Connecting to a BLE peripheral; Take your BLE knowledge to the next level. Here are the SIG specifications for the characteristics and services for BLE devices. In BLE, there are many events and operations that can be exchanged between a Peripheral and a Central. AccessDenied when accessing a BLE device's Services/Characteristics using Bluetooth Low Energy on Windows 10. ble_evt_dispatch() calls ble_lbs_on_ble_evt(), with a pointer to the static structure containing state information for the service, &m_lbs, and a pointer to the BLE event from the SoftDevice, p_ble_evt. 7. BleUuid. The access_cb field is an application callback that gets executed whenever a peer device attempts to read or write the characteristic. However, these services are implemented on top of the core BLE data connection profiles: GAP and GATT. This project is divided into two parts: Part 1 – ESP32 BLE server. Using 128-bit random values gives minimal chances of collisions for two parties generating Apr 5, 2017 · Re: BLE: How to add multiple characteristics in one service? Post by chegewara » Thu Nov 22, 2018 7:51 pm In this example you have array of services with 1 characteristic for every service, instead you can have array of characteristic for every service and duplicate this code for every characteristic added to service: May 16, 2019 · Bluetooth Low Energy, BLE for short, is a power-conserving variant of Bluetooth. Sep 3, 2020 · I'm looking for a list of Bluetooth GATT Services with a short description of each. Apr 20, 2012 · The adopted profiles / services / characteristics / descriptors use 16-bit UUIDs as seen on the official site. InsideBlue BLE Tool is a cross-platform Bluetooth LE utility. For GATT documentation, see Bluetooth Core Standard version 4, Vol 3, Parts F and G. BLE is limited to 125KBs-2MBs. Characteristics are the most point that you will interact with along with your BLE peripheral, so it is vital to grasp the concept. Jan 25, 2021 · And only first characteristics is created and no descriptor is added. 0+) and a Nordic BLE chip (NRF52832) to receive values from the chip on the android device. This can be added for any characteristic in the BLE component. For example, the SIG-adopted Battery Service contains one characteristic called the Battery Level. A Service is a grouping of BLE Roles, Devices, Characteristics, and Services. Initially, device will scan and connect to the peer device which is advertising with desirable peripheral Feb 19, 2023 · The hierarchical structure consists of profiles, services, and characteristics. I don't know why, who know why, please help me how to discover Services and Characteristics May 26, 2024 · BLE is designed for low-power, intermittent data transfer. Nov 21, 2023 · BLE devices use services and characteristics to transfer and store data. ” In other words, it is a set of rules describing how to bundle, present and transfer data using BLE. Services that are related are grouped into a profile. Top Aug 30, 2021 · The European version of the Miband 5 consist of 2 sensors: 6 axis IMU. Click on “Install” to install the ESP32 board definitions. System Management Service. com. Aug 7, 2023 · We got 3 services from the BLE Weighing device. Jun 16, 2021 · Till some time back, I was able to access definitions of BLE services, characteristics and descriptor definitions on Bluetooth. In order to use Bluetooth (Classic and Low Energy), a device must be compatible with the subset of device Profiles that implement its capabilities. The Bluetooth GATT (Generic Attribute Profile) governs communication between BLE devices via a dedicated connection. These services are discussed in detail in the BLE services section. This article will open with an overview of Bluetooth LE and the GATT Services, characteristics, and UUIDs. This hierarchy is strictly enforced for any device claiming GATT compatibility (essentially, all BLE devices sold), which means that all attributes in a GATT The Bluetooth Special Interest Group (SIG) specifies many BLE data transfer protocols that devices might implement, such as MESH for data network applications, BLP for blood pressure monitoring, HID/HOGP for keyboards and mice, etc. Services are used to break data up into logical entities, and contain specific chunks of data called characteristics. There used to be a page with links to PDF and XML files for each Aug 4, 2020 · GATT provides profile discovery and description services for the BLE protocol. On top of ATT protocol in the BLE stack, you have GATT and GAP. A Bluetooth® Low Energy peripheral will provide services, which in turn provide characteristics. There’s still so much more to interfacing with a BLE peripheral from an iOS app, including: Discovering services of a BLE peripheral; Discovering characteristics of a service May 22, 2023 · I have some problems with creating BLE services. Mar 12, 2024 · Services. 0 and higher: Maximum number of services: 10; Maximum number of characteristics: 30 Jun 16, 2021 · Till some time back, I was able to access definitions of BLE services, characteristics and descriptor definitions on Bluetooth. Using the example, I can create a service with a with one or two characteristics, but I'm struggling to create multiple services such as battery level service (0x180F) and environmental sensor (0x181A). (I don’t use third party packages) Connect, readout the services and the characteristics works well and fast, but: This project uses these features ; BLE GAP, GATT, Services and Characteristics, Serial UART, SAADC, TIMER and GPIO. The best way to get started with BLE and the ESP32 is to start by learning about basic concepts like BLE Server and Client, GATT, BLE Profiles, Services, and Characteristics. Services: Services represent different functionalities offered by a BLE peripheral. I`m using BLE GATT Configurator for this purpose. Bluetooth performs data transfers at 1-3MBs. Some generic UUIDs are reserved by the Bluetooth SIG and should only be used by specific metrics. Dec 19, 2017 · BluetoothGatt. – Jun 7, 2021 · We could then create an instance of this model with the three color values: let rgbColor = RGBColor(red: red, green: green, blue: blue) But if we want to read several different characteristics or if any of the field’s types is not. Sep 8, 2020 · Learn the major components of Core Bluetooth, basic steps for scanning, connecting to, and interacting with a BLE peripheral, common pitfalls & BLE on iOS. characteristicsForService(serviceUUID : UUID) : Promise <Characteristics> I'm looking at making a weather station using an ESP32 Dev that uses Bluetooth Low Energy (BLE) to talk back to another ESP32 Dev in the house. bk wk bm dn ur zj fo gn vk hn