Developing a Smart Pendant with BU03 for Precise Distance Measurement to Mobile Phones!

Preface

A smart pendant developed based on the new UWB module of Ai-Thinker - BU03, which can accurately measure the distance to mobile phones!

 

Good news: It has an accuracy of ±10cm and also supports reconnection! And the maximum detection distance is 14 meters.

 

Bad news: It only supports iPhones above iPhone 11! (Because only iPhones above iPhone 11 have UWB function)

Ⅰ. Project Functions

Precise testing with mobile phones - Achieved

Automatic reconnection - Achieved

Low power consumption - Under development

 


Ⅱ. Instructions for Use

Since the low power consumption function is still under development, it is not yet perfect. After installing the button battery, just turn the power switch to the ON position to turn it on.

After turning it on, you can use an iPhone for testing. In the App, select the device with the Bluetooth name “NRF52832DK(xxx)” and pair and connect to see the distance from the BUTag.

Ⅲ. Test App

Download “Qorvo NI Background”

Ⅳ. Project Parameters

Module: BU03 UWB Module

Main Control: NRF52832 Bluetooth Chip (mainly because there is ready-made code available)

Connection UWB Distance: 5 meters (stable), maximum 13 meters

Average Power Consumption: 26mA

 

Ⅴ. Principle Analysis

BU03 uses SIP communication, and it is not recommended to change the pins of NRF52832 connected to BU03!!

 

Note: The author has personally stepped on this mine and made changes to the board, and even sent it for 12-hour urgent processing (cost ￥290 (including tax)).


There are 2 points to note in the communication process with iPhones:

  • Has BLE started broadcasting and connected successfully?
  • Has the UWB data transmission stopped and the connection been disconnected?

 

Ⅵ. Assembly Process

Size of Knurled Nut

The knurled nut is recommended to be M2 with a diameter of 3mm and a length of 2mm. Use a soldering iron to hot-press it into the screw hole of the shell:

Installation Process

Open Source Address

 

BUTag - UWB Precise Ranging Pendant: https://oshwhub.com/ai-thiner_openteam/butag_pcb

 

Ⅶ. Precautions

  • BUTag can only be used to experience the UWB function at present, do not expect too much.
  • BUTag almost all uses 0402 package, welding is difficult. If you want samples, you can contact Ai-Thinker official (+86 18022036575).
  • There is no reverse connection circuit designed for the button battery holder. Please pay attention to the positive and negative when installing the button battery.

The author has tried it, and currently, the distance from BUTag can be seen in real-time on the mobile App. Except for experiencing the performance of UWB, BUTag seems to be unable to do anything else.

But then I thought, is the approach start of the car key using UWB?

When BUTag is in the bag, can the anti-loss function also be realized? For example, set an alarm when the distance exceeds the set value in the App? Or a search function like AirPods?