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Bluetooth Smart Lock Application Module Solution Based on Realtek RTL8762AG

Published time : 2020-03-17 RTL8762AG realtek bluetooth
From this article, you will know the good news about the smart lock by using bluetooth in the future.

Solution Introduction

Modern people almost always have a large number of keys, such as home lock keys, car keys, locomotive keys, anti-theft lock keys, etc., which are very heavy !! If you accidentally lose them, it may be tiring to rekey. Bluetooth E-Lock application, using a mobile phone with one hand, with APP and Bluetooth remote control to replace the traditional key lock. The trouble of bringing a large number of keys is reduced, and when the loss situation occurs, the user authentication through the mobile APP can be resumed to continue to use.

Bluetooth E-Lock, can be divided into three categories of applications:

Specifications and functions

Operation: Download APP software, search cabinet lock and set name & password, authorize others to use unlimitedly

Add remote control function, each set of cabinet locks can be equipped with “16 remote controls (need to be paired)”

Record: Can record 2048 locks

Power consumption: about 80uA

Security: Three decryption procedures

Forgot password: there is a reset key inside the lock, which is used to restore the original factory settings

Encryption and decryption of communication transmission data. The password is 16 bytes. The length of each byte is 0x00 ~ 0xFF.

1 set of main management password can manage 4 sets of sub-user passwords, and the sub-users cannot change the main manager password and their own password to achieve complete anti-theft and super security

APP interface introduction

BT Module

Supports Bluetooth 4.2 specifications

Integrated MCU that can execute Bluetooth protocol 

Support multi-level low-power state; support built-in 32KHz OSC or external 32KHz clock and input for low-power mode

LE L2CAP Connection Oriented Channel, LE low duty directed advertising, LE data length extension feature

Support GAP, ATT / GATT, SMP, L2CAP. For GAP Central, Peripheral, Observer and Broadcaster Roles

Support AES128 / 192/256 encryption and decryption engine

1 UART interface, 1 SPI interface, 1 I²C interface, 4 PWMs interface, 1 ADC (12-bit 39KHz Sigma-Delta)

Up to 16 GPIOs, 8 timers, 3 configurable LED pins, hardware Keyscan and Quad-decoder, built-in IR transceiver, real-time counter (RTC)

Software Development Environment

Compilation environment Tool Chain

Keil MDK-ARM Lite V5 or later

SDK should be compiled by Keil Microcontroller Development Kit (MDK), in order to avoid compatibility problems of ROM executable programs and applications,

It is recommended to use the following version or later

Platform setting instructions


Hardware design

Introduce the design of the antenna part, the quality of the antenna design, and the reception sensitivity of the BT signal

PCB antenna

Although the PCB antenna occupies a large PCB area, it has the advantages of low cost, easy production, and sufficient wireless communication distance.

The antenna is usually a quarter-wave straight line. In portable devices, in order to reduce the size of the portable device, the antenna is often designed as a curve.

In the PCB antenna setup, the antenna size and performance conflict with each other. Small-sized antennas and wide bandwidths are generally difficult to achieve at the same time. Therefore, the antenna headroom is a key factor in antenna design. When designing the antenna clearance area of the PCB, it is highly recommended to refer to the figure below.

The headroom area means that no metal other than the antenna itself is allowed. Among the four different designs of Fig. (A) -Fig. (D), Fig. (A) has the best performance, which guarantees the ideal And clear the remaining GND area.

When the allowable clearance area is not large enough, you can refer to the design shown in Fig. (C). Although the antenna line is about 1/4 wavelength, the antenna performance and bandwidth are also limited.

According to empirical reference, it is forbidden to place any metal in the clearance area, otherwise the antenna performance will be greatly interfered.

Although Fig. (D) meets the above requirements, its antenna performance is not as ideal as Fig. (A). This is because the GND plane is exactly in the antenna radiation direction, which results in antenna performance.

Thimble antenna

A thimble antenna is also a common antenna solution, which has certain requirements on the housing.

The space between the housing and the PCB must be greater than 10mm to ensure good antenna radiation characteristics.

Use thimble antenna, RF block needs to add DC block capacitor to prevent chip RF damage when soldering thimble

PCB Layout


Scene application diagram


Product entity diagram


Solution block diagram


Core technology advantages

CPU processor

-ARM Cortex-M0 @ 53MHz

Larger temporary storage capacity

-64KByte RAM

-256kByte Embedded Flash

-384kByte ROM

-2kByte Efuse

High-speed transmission capability and better RF sensitivity

-Throughput: Up to 75KB / s

-RX Sensitivity: -95dBm @ 3V

Smaller packaging and lower power consumption

-Chip Size: 5 x 5 mm

-Power Consumption: Less than 1uA

More GPIOs (x16) settings

-Key Scan / IR (TX & RX) / Quad Dec / RTC / LPCOMP

-I2C x 2 / SPI x 2 / Timer x 6

-ADC / GDMA / WDT

-UART (Data, HCI, Log)

Bluetooth specification

-Support BlueTooth 4.2 Low Energy

Solution specifications

Bluetooth Standard

-V4.2 LE Specifcation

Modulation Scheme

-GFSK, MSK

Data rate

-1Mbps, 2Mbps

Data Encryption

-AES 128 bit

RF Frequency Range

-2.402 ~ 2.480 GHz

Power Consumption

-RX: 17.5 mA

-TX: 18.3 mA (0dbm)

-4us Wake-Up: 270uA

-Sleep Timer On: 1uA

-External Interrupts: 0.5uA

Temperature

-Storage: -30 ~ 85 ° C

-Operating: 0 ~ 70 ° C

Key Components

No. Part Number Manufacturer
1 RTL8762AG Realtek