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README.md
README.md
 
 
a-node.ino
a-node.ino
 
 
battery.ino
battery.ino
 
 
leds.ino
leds.ino
 
 
measure_board.pdf
measure_board.pdf
 
 
nrf-sensor-server.ino
nrf-sensor-server.ino
 
 

README.md

nRF52840 Sensor Server

Look at the main README.md for an overview of the project to understand the context of this project.

Use Arduino IDE to compile and upload the code to the XIAO BLE Sense.

Hardware used :

A-Node only :

Libraries used:

Configuration

Node type

This code is used for the M-Node, A-Node and S-Node. Define NODE_TYPE to M_NODE, A_NODE or S_NODE to compile the code for the M-Node, A-Node or S-Node.

Button

If you want to use the button, define USE_BUTTON to 1.

See [Button](#how to use) for more information on how to use the button.

Pinout

BUTTON_PIN and SLEEP_PIN can be changed in the nrf-sensor-server.ino file.

Default values if using the custom PCB:

  • BUTTON_PIN = 2 (correspond to BTN S2)
  • SLEEP_PIN = D0

Battery level

Every BATTERY_SEND_INTERVAL (ms), the battery level is sent to the Main-Node. You can change the interval, as well as the battery level calculation in the battery.ino file.

Other options.

BLE service UUIDs and characteristics UUIDs can be changed in the nrf-sensor-server.ino file.

Bluetooth discovery duration, as well as the sleep duration, can be changed in the nrf-sensor-server.ino file.

How to use

General usage

LED

The Serial LED is used to indicate the state of the node.

  • Slow 🔴 blink : disconnected
  • Fast 🟢 blink : pairing (device is discoverable)
  • Slow 🟢 blink : connected

Button

BT_User (marked as S2 on the PCB) can be used to start the pairing process when device is disconnected.

Note : If USE_BUTTON = 0, the the device will always be in pairing mode while not connected.

M-Node

The M-Node will send the gyro and accelerometer data to the Main-Node when connected at a SEND_INTERVAL rate (Hz).

It can be put to sleep by putting a LOW signal on the SLEEP_PIN pin. It can be woken up by putting a HIGH signal on the SLEEP_PIN pin.

A-Node

The A-Node will send the wind speed and direction to the Main-Node when connected at a SEND_INTERVAL rate (Hz).

Note : The send interval might not be respected because of the delay required to read the wind speed and direction using RS485.

S-Node

The S-Node will listen to the Sleep BLE Characteristic (uuid: 2c41ce1f-acd3-4088-8394-b21a88e88142) of the Sleep Service (uuid 63e4eb54-b0bc-4374-8d2a-5f08f951230a).

When the value is TRUE, it will put the M-Node to sleep by putting a LOW signal on the SLEEP_PIN pin. When the value is FALSE, it will wake up the M-Node by putting a HIGH signal on the SLEEP_PIN pin.

Understanding the code

The code is split into 4 files :

  • nrf-sensor-server.ino : main file, contains the setup and loop functions.
  • battery.ino : contains the battery level calculation and sending.
  • a-node.ino : contains the A-Node specific code. (for RS485 communication)
  • leds.ino : contains the LED functions for controlling serial LED.

nrf-sensor-server.ino

The setup function will initialize the BLE service and characteristics, the battery level, the button and the sleep pin.

The loop function will handle the BLE events, the button press, the sleep signal and the battery level sending. It will call the node specific functions (M-Node, A-Node or S-Node) to get and send the data.

battery.ino

The battery level is calculated using the voltage divider method. The battery level is sent to the Main-Node every BATTERY_SEND_INTERVAL ms.

a-node.ino

The A-Node specific code is in this file. The RS-FXJT-N01 Wind direction transmitter and the RS-FSJT-N01 Wind speed transmitter are read using RS485 communication. They wait for a specific frame to be sent to start sending the data.

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