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Documentation > GR551x Developer Guide/ Introduction Copy URL


The Goodix GR551x System-on-Chip (SoC) is a single-mode low-power SoC that supports Bluetooth 5.1. It can be configured as a Broadcaster, an Observer, a Central, or a Peripheral, and supports the combination of all the above roles, making it an ideal choice for Internet of Things (IoT) and smart wearable devices.

Based on ARM® Cortex®-M4F CPU core, the GR551x SoC integrates the Bluetooth 5.1 Protocol Stack, a 2.4 GHz RF transceiver, on-chip programmable flash memory, RAM, and multiple peripherals.

GR551x SoCs are available in multiple packages (see Table 1) that meet your diverse project demands.

Table 1 GR551x series
CPU Cortex®-M4F Cortex®-M4F Cortex®-M4F Cortex®-M4F Cortex®-M4F Cortex®-M4F Cortex®-M4F
RAM 256 KB 256 KB 256 KB 256 KB 256 KB 128 KB 128 KB
Flash 1 MB 512 KB N/A 1 MB 1 MB 512 KB 512 KB
Package (mm)


(7 x 7 x 0.75)


(7 x 7 x 0.75)


(7 x 7 x 0.75)


(5.3 x 5.3 x 0.88)


(3.5 x 3.5 x 0.60)


(5 x 5 x 0.75)

QFN40 (5 x 5 x 0.75)
I/O Number 39 39 39 39 29 22 22
  • GR5515IENDU and GR5513BENDU are embedded with wide-voltage Flash, with Flash power supply from 1.65 V to 3.6 V.
  • GR5515I0NDA supports external wide-voltage Flash (range: 1.65 V–3.6V).

GR551x SDK

The GR551x SDK provides comprehensive software development support for GR551x SoCs. The GR551x SDK contains BLE Protocol Stack (BLE Stack) APIs, System APIs, peripheral drivers, a tool for generating and downloading .hex files, project example code, and related user documents.

The GR551x SDK version mentioned in this document is applicable to all GR551x SoCs.

BLE Stack

The architecture of BLE Stack is shown in Figure 1.

Figure 1 BLE Stack architecture

The BLE Stack consists of the Controller, the Host-Controller Interface (HCI), and the Host.


  • Physical Layer (PHY) supports 1-Mbps and 2-Mbps adaptive frequency hopping and Gaussian Frequency Shift Keying (GFSK).
  • Link Layer (LL) controls the RF state of devices. Devices are in one of the following five modes, and can switch between the modes on demand: Standby, Advertising, Scanning, Initiating, and Connection.


  • HCI enables communications between Host and Controller, supported by software interfaces or standard hardware interfaces, for example, UART, Secure Digital (SD), or USB. HCI commands and events are transferred between Host and Controller through HCI.


  • Logical Link Control and Adaption Protocol (L2CAP) provides channel multiplexing and data segmentation and reassembly services for upper layers. It also supports logic end-to-end data communications.
  • Security Manager (SM) defines pairing and key distribution methods, providing upper-layer protocol stacks and applications with end-to-end secure connection and data exchange functions.
  • Generic Access Profile (GAP) provides upper-layer applications and profiles with interfaces to communicate and interact with protocol stacks, which fulfills functions such as advertising, scanning, connection initiation, service discovery, connection parameter update, secure process initiation, and response.
  • Attribute Protocol (ATT) defines service data interaction protocols between a server and a client.
  • Generic Attribute Profile (GATT) is based on the top of ATT. It defines a series of communications procedures for upper-layer applications, profiles, and services to exchange service data between GATT Client and GATT Server.

For more information about Bluetooth LE technologies and protocols, visit the Bluetooth SIG official website:

Specifications of GAP, SM, L2CAP, and GATT are provided in Bluetooth Core Spec. Specifications of other profiles/services at the Bluetooth LE application layer are available on the GATT Specs page. Assigned numbers, IDs, and code which may be used by Bluetooth LE applications are listed on the Assigned Numbers page.

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