Introduction

The document gives details on how to use Wirepas Positioning embedded software in order to develop your own hardware for a Wirepas Positioning System.

It gives the list of hardware recommendations for building tags and anchors and points you to the right documents describing the Wirepas Positioning embedded software.

What you’ll learn

• What are the hardware requirements for a Wirepas tag and a Wirepas anchor ?
• Where to find the tag and anchor reference software
• What API documents are available for your backend integration project ?
• How to test your tags or anchors once they are programmed

What you’ll need

• An understanding of Wirepas positioning system and its components is required. Please read Wirepas Positioning system Overview [1].
• To know:
  1. How To Install SDK and Build an Application [2]
  2. How To Flash Wirepas Application [3]
• Even if it is not mandatory, you will preferably need a basic understanding of Wirepas mesh. For further information on Wirepas mesh, please refer to Wirepas Mesh Concept document [4] 

How to engage in a Wirepas Positioning project: 

You are a hardware vendor, willing to develop and manufacture Wirepas asset tags and / or Wirepas anchors. Wirepas delivers a complete embedded software which allows you to program asset tags and anchors.

Note: A Wirepas Software License is required to access Wirepas software and build the Wirepas positioning application, please contact your Wirepas sales [5] representative to request a license.

Wirepas positioning system overview

Wirepas Positioning system Overview [1] gives an introduction to Wirepas positioning system, explains how it works and which building blocks it includes. 

The diagrams below reminds the various hardware building blocks of a Wirepas Positioning system and their features.

Tags and Anchors Hardware requirement 

Here are few recommendations to guide you on how to build your own Wirepas compliant tags and anchors

The hardware requirements for the Wirepas tags and anchors are as follow:

Radio

The tags and anchors should include one of the supported Wirepas radio chipset.

• Nordic Semiconductor: nRF52832, nRF52833 or nRF52840 with a 32kHz crystal
• Silicon Labs: EFR32xG21 (for anchors) or EFR32xG22 (for asset tags) with a 32kHz crystal

Please refer to the corresponding hardware reference manual for detailed recommendation nRF528xx 2.4 GHz Hardware Reference Manual [7] or Silabs EFR32 Hardware Reference Manual [8]

On / Off

• In order to save battery power, the tags and anchors are recommended to include a switch on/ off method.
• The tags are by default OFF (or in deep sleep) when they are out from the factory, so they do not waste battery during storage.
• The tags get out of deep sleep through:
  1. NFC – this is the preferred wake-up / sleep and provisioning mechanism.
  2. A tape on the battery to be physically removed during the installation. (if NFC is not supported)

Accelerometer in the asset Tags

In order to optimize the power consumption of the asset tags the measurement reporting frequency is reduced when the asset tags are static and increased when they are moving. Therefore, the Wirepas Positioning application assumes the asset tags include an accelerometer. The Wirepas Positioning application supports natively the STMicroelectronics LIS2DH12 and LIS2DW12 accelerometers; but since the source code is provided, you can easily replace the accelerometer driver by the one of your choice. 

Unique Identifier

Tags and anchors have a unique identifier (called Node address in Wirepas terminology) which shall be readable by user and from a smartphone:

o   Bar code or QR code

o   through NFC – if NFC is available (preferred).

o   BLE Beacon broadcasting the UID of the Tag

Important note on Unique Identifier (Node address):

In Wirepas Positioning application, the Node address is directly derived from the hardware chip ID provided by the chipset manufacturer. This is the best way to secure that every tag ID has the highest probability to be unique. The system behavior is not guaranteed if two or more tags operating in the same network have the same “Unique” Identifier. It is therefore required to keep the Node address as provided by the Wirepas Positioning application and not attempt to change it.

Battery capacity:

The battery capacity should be selected to cover the expected lifetime for the end-customer use case. Of course the power consumption of the product depends on many parameters among them the Chipset used, the sensors, the hardware design and the software (Wirepas stack + Application).

Wirepas provides complete power consumption KPI [13] for the various chipset supported to help the Hardware manufacturer to design its product.

To ease the dimensioning Wirepas also provides Dimensioning tools helping to understand the power consumption of the system:

• For the Tags, a Tag power consumption estimation tool is provided together with this document and helps to dimension the different parameters (Battery capacity, performance). See: Wirepas Positioning Tags Battery Calculator.
• For the Anchor, please refer to the Wirepas Positioning Dimensioning Guide [9] which includes a power estimation tool for the Anchors.

The table below summarizes the typical achievable performance for Tags and Anchors:

Numbers based on nRF52832 with DCDC.

Tag and anchors Software

In order to accelerate the software development, Wirepas provides a complete positioning application (including a positioning library) which runs on the RuuviTag. The Wirepas Positioning Application is delivered in source code so it can be adapted:

• to support other accelerometer IC than the one provided
• to change the mapping of the IOs if needed
• to support the EFR32xG22 if required

Wirepas Positioning Application is available as part of the Wirepas SDK [10]. The source code of the Wirepas Positioning Application software is provided here [11]

If used as is, this application provides compatibility with existing tags, anchors and gateways supporting Wirepas mesh v5.1 onward. The 2nd release of Wirepas Positioning library and application has the following features.

Information on Wirepas Positioning Library can be found in Wirepas Positioning Application Reference Manual [12]

You can build the Positioning application software according to your board hardware specification (refer to How To Install SDK and Build an Application document [2]). Once the software is built, you can flash the positioning application hex file to your tag or anchor (refer to How To Flash Wirepas Application [3]).

References:

[1] Wirepas Positioning system Overview
[2] How To Install SDK and Build an Application
[3] How To Flash Wirepas Application
[4] Wirepas Mesh Concepts
[5] Wirepas sales contact details
[7] nRF528xx 2.4 GHz Hardware Reference Manual
[8] Silabs EFR32 Hardware Reference Manual
[9] Wirepas Positioning Dimensioning guide
[10] Wirepas SDK
[11] Wirepas Positioning Application software
[12] Positioning Application Reference manual
[13] Wirepas mesh v5.x KPI

Revision History

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