Gravity: BLE Sensor Beacon Wiki - DFRobot

Introduction

This Gravity wireless BLE Sensor Beacon with built-in 11-bit ADC is capable of collecting data from digital and analog sensors and broadcasting via Bluetooth. And users can access the sensor data within broadcasting range on a Bluetooth-equipped device like a smartphone, ESP32, etc.
The BLE sensor beacon is integrated with low power BLE 5.3 technology, and its data format can be configured as iBeacon, Eddystone, custom format, etc. Besides, users can configure broadcast data format, content and time intervals on graphical interface as per their needs, which allows configuring a BLE beacon without any programming.
After configuration, it will run as a Bluetooth beacon when powered on, and collect and broadcast data automatically according to the settings. These sensor beacons can be used as IoT sensor nodes for data collection in many scenarios such as smart farms, offices, factories, and warehouses.

Note: Gravity: BLE beacon module needs to be configured with a 3.3V USB-TTL tool.

Specification

Pinout

NO. Name Description
1 Power Input 1.2-5.5V DC power input
2 Burning/Debugging Used for module debugging and burning
3 Sensor Signal Input "A": Sensor signal input
"-": Sensor power supply GND
"+": Sensor power supply VCC
4 Sensor VCC Select Short circuit: 3.3V continuous power supply
Disconnected (default): supply power only when broadcasting

Power supply description

When using a 1.2-3.3V power supply to power the beacon, the supply voltage at the sensor side follows the input voltage, for example, if a 1.5V AAA battery is used to power the beacon, the beacon will work normally and will provide 1.5V to the sensor. When using a 3.3-5.5V power supply to power the beacon, the supply voltage at the sensor side is a stable 3.3V.

Quick Start Guide

The guide demonstrates how to get sensor data by mobile app and ESP32 when the data is configured in custom format.

1. Requirements

2. Configure Sensor Beacon

Note: The module can only be burned once, so don't click "Burn/Program" before confirming the configuration information. Test the module through "Run in RAM", which can be used infinitely before burning. The system will reset when powered off.

This Gravity: BLE sensor beacon supports three advertising sets. Tick to Enable it. One of them is enabled by default; click Edit to enter the config page.

Three data formats are supported: iBeacon, Eddystone and Custom. This tutorial mainly uses custom data format.

Check "Device Name", and enter "Gravity: Sensor Beacon" or other names. So later it will be easy to scan and find the device on the mobile phone or ESP32 by name.

Check "Manufacturer Specific Data", and click "EDIT" to configure data.

Only one analog data is configured here. Select "ADC CH1" in the drop-down menu, check "Big Endian", click "Append to Data", and then "0x<ADC CH1 2byte 1 0>" appears in the window. Click OK to exit.

The advertising interval and address are set here. Make changes as required, and click OK to exit when done. Now the advertising data format is configured, and the module will broadcast data once every 1s.

Next, configure ADC. The Gravity: BLE sensor beacon uses IO5 for analog acquisition, so enable "ADC Channel 1 MPGIO 5" in the ADC config page, and click Edit to set.

Change the unit to 0.001 for easy calculation, which has little effect on the accuracy. But if high accuracy is required, leave it alone. Since the analog input voltage is divided (2.06) in the circuit, it is necessary to remap the divided voltage value.

Change Value of 1.4V to 2.898

Change Value of 0.4V to 0.828

Now the ADC sampling config is completed, and the data broadcasted by the beacon will be the voltage of the "sensor signal input"; unit is mV.

Since MGPIO 5 serves as ADC input, it needs to be configured as "disable".

MGPIO 6 will be used as a power supply for the sensor, so configure it as "output high" "pull up" and "latch" to keep it outputting a high 3.3V for powering sensor.

As shown at the lower left corner of the page, Set #1, ADC Channel 1, MGPIO5 and MGPIO6 are enabled.

Connect hardware according to the connection diagram.

Click "Probe" at the upper right corner to refresh the port, then select the corresponding port, and click "Connect". A pop-up window will appear after a successful connection.

Click "Run in RAM", and a pop-up window will appear when it's done.

Note: The module can only be burned once, so don't click "Burn/Program" before confirming the configuration information. The module can be tested through "Run in RAM", which can be used infinitely before burning. The system will reset when powered off.

3. Get Data via Mobile App

"Gravity: Sensor Beacon" is the Device Name set in step 4 of the tutorial for beacon config;

"06:05:04:03:02:01" is the address set in step 6;

"0X00E3" is the ADC-sampled data set in step 5.

The known sensor data sampled by the beacon is "0X00E3", equalling 227 when converted to a decimal number, which means the voltage value sampled by the beacon is 227mV.

The sensor connected is LM35 temperature sensor. And LM35 wiki shows the relationship between its output voltage and temperature: 10mV for one degree Celsius, which means the sensor temperature data broadcasted by the beacon is 22.7°C.

4. Get Data with ESP32

/*
   Based on Neil Kolban example for IDF: https://github.com/nkolban/esp32-snippets/blob/master/cpp_utils/tests/BLE%20Tests/SampleScan.cpp
   Ported to Arduino ESP32 by Evandro Copercini
   Changed to a beacon scanner to report iBeacon, EddystoneURL and EddystoneTLM beacons by beegee-tokyo
*/

#include <Arduino.h>
#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEScan.h>
#include <BLEAdvertisedDevice.h>
#include <BLEEddystoneURL.h>
#include <BLEEddystoneTLM.h>
#include <BLEBeacon.h>
#define ENDIAN_CHANGE_U16(x) ((((x)&0xFF00) >> 8) + (((x)&0xFF) << 8))

float Sensor_Data;
int scanTime = 5; //In seconds
BLEScan *pBLEScan;

class MyAdvertisedDeviceCallbacks : public BLEAdvertisedDeviceCallbacks
{
    void onResult(BLEAdvertisedDevice advertisedDevice)
    {
      if (advertisedDevice.haveName())
      {
        if(String(advertisedDevice.getName().c_str()) == "Gravity: Sensor Beacon"){
          Serial.print("Device name: ");
          Serial.println(advertisedDevice.getName().c_str());
          std::string strManufacturerData = advertisedDevice.getManufacturerData();
          uint8_t cManufacturerData[100];
          strManufacturerData.copy((char *)cManufacturerData, strManufacturerData.length(), 0);
          Serial.printf("strManufacturerData: %d ", strManufacturerData.length());
            for (int i = 0; i < strManufacturerData.length(); i++)
            {
              Serial.printf("[%X]", cManufacturerData[i]);
            }
            Sensor_Data = int(cManufacturerData[3]);
            Serial.println();
            Serial.print("Voltage:");Serial.print(int(Sensor_Data));Serial.println("mV");   
            Serial.print("Temp_LM35:");Serial.print(Sensor_Data/10);Serial.println("℃");      
            Serial.println("------------------");       
        }        
      }
    }
};
void setup()
{
  Serial.begin(115200);
  Serial.println("Scanning...");

  BLEDevice::init("");
  pBLEScan = BLEDevice::getScan(); //create new scan
  pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());
  pBLEScan->setActiveScan(true); //active scan uses more power, but get results faster
  pBLEScan->setInterval(100);
  pBLEScan->setWindow(99); // less or equal setInterval value
}
void loop()
{
  // put your main code here, to run repeatedly:
  BLEScanResults foundDevices = pBLEScan->start(scanTime, false);
  pBLEScan->clearResults(); // delete results fromBLEScan buffer to release memory
  delay(2000);
}

5. Confirm Data & Burn

Advanced Application

1. Broadcast Eddystone TLM Data

The Eddystone TLM comes with temperature data obtained from the temperature sensor inside the beacon chip. But it may be affected by the heat generated by the chip.

When configuring Eddystone TLM, select "Eddystone" in "Advertising Data Format", and "TLM Frame" in "Eddystone - Settings". Keep parameters like broadcast interval and address as default or make changes when necessary.

2. Power Supply for High-power Sensor

When using MGPIO6 as power output, it may fail to drive some high-power sensors due to weak loading capacity. So there are jumper pads designed on the back of the beacon board, which allows to power sensor through onboard LDO by short-circuiting, thus providing stabler 3.3V voltage with stronger electrical load capacity.

3. Dynamic Power Supply Control

Dynamic power supply control means only supplying power to the sensor during broadcast, and stopping powering when the broadcast ends. For this purpose, you need to set MGPIO6 as "wakeup high, sleep low" and Latch as "disable".

The sample config file can be loaded directly after downloading: DynamicPower.zip

4. Avoid Packet Loss During Long Interval

When the advertising interval is set to 10s or even longer, if the receiver fails to receive, it has to wait for the next broadcast from the beacon after 10s, in which the failure risk may still exist. In this case, it is recommended to do multiple broadcasts after the interval.

The steps are shown below:

Instructions for NanoBeacon Config Tool

For more information on the use of the NanoBeacon Config Tool, see the software user guide: NanoBeacon Config Tool User Guide EN.pdf The user guide uses the "Beacon development kit" and when using the Gravity: BLE sensor beacons, the 3.3V USB-TTL tool can be used directly.

FAQ

For any questions, advice or cool ideas to share, please visit the DFRobot Forum.

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