Hardware: Hive Interface Board 5

Analog Devices AD7124-8 Eval Board (left) connected to the Nordic nRF52840 Preview Development Kit (right)

Introduction

After a failed attempt at Hive Interface board version 0.4, work has begun on version 0.5.

A different approach from version 0.4 was taken. An Analog to Digital Converter (ADC) evaluation board (Analog Devices EVAL-AD7124-8SDZ) and the Nordic nRF52840 Preview Development Kit (PDK) were purchased.

This allows the software to be developed and tested before the hive interface board is designed.

• Initial development of the ADC driver was done on the PI.
• nRF52840 development tools and code.

Goal

Create a low power, battery operated, wireless scale based on the Internet of Things (IOT) paradigm with extended communication range and a high performance multi-channel Analog to Digital Converter (ADC).

Features

• AD7124-8 24 bit ADC with 8 differential inputs and digital filters capable of 120 dB notch at 50 Hz and 60 Hz.

Provides independent channels for each of the 4 load cells or four scales with 4 loads cells in parallel.

• Bluetooth Low Energy (BLE) support

Uses the Nordic nRF52 32 bit ARM processor with GPIO lines and eight 16 bit ADC inputs.

• 40 pin header plugs into a Pi.

The board can run from the Pi without the nRF52840 as a replacement for the HX711. The nRF52840 can be programmed from the Pi.

Configurations

Configuration A

Hive Interface Board plugged into the Pi.

• Powered by the Pi
• Sensors can be read by the Pi.
• Without optional nRF52840 installed, board can be operated like ver 0.3.
• nRF52840 (if installed) can be programmed from the Pi.
• Supports up to 8 load cells (4 scales consisting of 2 load cells each)

Configuration B

Hive Interface Board separate from the Pi. The Pi is used for data storage, visualization and forwarding to the cloud via WiFi, Ethernet or cellular modem.

• Lower power requirement at the hive.
• Communication to the PI is via UDP over BLE4.

Configuration C

• Pi is operated as BLE5/6LoWPAN to IP6 thread router using the nRF52840 radio since the Bluetooth radio on the Pi does not support BLE5 (only BLE4).
• Pi can also be used for local data storage and visualization.
• Hive Interface board uses BLE5 and 6LowPAN for long range low power consumption
• Three instrument boards

1. hive weight
2. Temperature/Relative Humidity and Microphone inside hive
3. Temperature/Relative Humidity and LUX outside hive (one per apiary).

• Can form a mesh network for data relay.

Development

 NRF52840 Development shows how to get Segger J-Link command line tools running on Linux Debian
 NRF52840 Development Code is a test program that runs on the nRF52840 and talks to the AD7124
 NRF52840 Thread NCP documents running a thread router on the Pi using the nRF52840 dongle as a Network Co-Processor (NCP).

Resources

Data Sheets

AD7124-8 Data Sheet (PDF 1.7 MB 92 pages)
nRF52840 (PDF 6.4 MB 696 pages)

AD7124-8 (pdf)

Evaluation Boards

EVAL-AD7124-8SDZ User Guide (PDF 4.8 MB 40 Pages)

nRF52840 Preview Development Kit v0.9.x User Guide v1.0 (PDF 9.1 MB 41 Pages)