Show Bluetooth LE Sensor readings on LCD screen connected to STM32

1. Introduction

About the Code

void USBH_CDC_ReceiveCallback(USBH_HandleTypeDef *phost)
{
if(phost == &hUsbHostFS)
{
// Handles the data recived from the USB CDC host, here just printing it out to UART
rx_size = USBH_CDC_GetLastReceivedDataSize(phost);
HAL_UART_Transmit(&huart3, CDC_RX_Buffer, rx_size, HAL_MAX_DELAY);
// Copy buffer to external dongle_response buffer
strcpy((char *)dongle_response, (char *)CDC_RX_Buffer);
// Reset buffer and restart the callback function to receive more data
memset(CDC_RX_Buffer,0,RX_BUFF_SIZE);
USBH_CDC_Receive(phost, CDC_RX_Buffer, RX_BUFF_SIZE);
}
return;
}
void dongle_interpreter(uint8_t * input)
{
if(strlen((char *)input) != 0)
{
if(strstr((char *)input, "\r\nADVERTISING...") != NULL)
{
isAdvertising = true;
}
if(strstr((char *)input, "\r\nADVERTISING STOPPED") != NULL)
{
isAdvertising = false;
}
if(strstr((char *)input, "\r\nCONNECTED") != NULL)
{
isConnected = true;
HAL_GPIO_WritePin(GPIOE, GPIO_PIN_1, GPIO_PIN_SET);
}
if(strstr((char *)input, "\r\nDISCONNECTED") != NULL)
{
isConnected = false;
HAL_GPIO_WritePin(GPIOE, GPIO_PIN_1, GPIO_PIN_RESET);
}
if(strstr((char *)input, "L=0") != NULL)
{
isLightBulbOn = false;
//HAL_GPIO_WritePin(Lightbulb_GPIO_Port, Lightbulb_Pin, GPIO_PIN_RESET);
lcd_clear();
writeToDongle((uint8_t*)DONGLE_SEND_LIGHT_OFF); uart_buf_len = sprintf(uart_tx_buf, "\r\nClear screen\r\n");
HAL_UART_Transmit(&huart3, (uint8_t *)uart_tx_buf, uart_buf_len, HAL_MAX_DELAY);
}
if(strstr((char *)input, "L=1") != NULL)
{
isLightBulbOn = true;
writeToDongle((uint8_t*)DONGLE_SEND_LIGHT_ON);
lcd_clear(); lcd_write(input); } }
memset(&dongle_response, 0, RSP_SIZE);
}
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
MX_USB_HOST_Process();
/* USER CODE BEGIN 3 */
// Simple handler for uart input
handleUartInput(uartStatus);
// Inteprets the dongle data
dongle_interpreter(dongle_response);
// Starts advertising as soon as the Dongle is ready.
if(!isAdvertising && !isConnected && isBleuIOReady)
{
HAL_Delay(200);
writeToDongle((uint8_t*)DONGLE_CMD_AT_ADVSTART);
isAdvertising = true;
}
}
/* USER CODE END 3 */

Using the example project

What we will need

Importing as an Existing Project

Running the example

Send Sensor data to LCD screen from a web browser

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<link
href="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/css/bootstrap.min.css"
rel="stylesheet"
integrity="sha384-1BmE4kWBq78iYhFldvKuhfTAU6auU8tT94WrHftjDbrCEXSU1oBoqyl2QvZ6jIW3"
crossorigin="anonymous"
/>
<title>Bluetooth LE Air quality sensor data to LCD screen</title>
</head>
<body class="mt-5">
<div class="container mt-5">
<img
src="https://www.bleuio.com/blog/wp-content/themes/bleuio/images/logo.png"
/>
<h1 class="mb-5">Bluetooth LE Air quality sensor data to LCD screen</h1>
<div class="row">
<div class="col-md-4 pt-5">
<button class="btn btn-success mb-2" id="connect">Connect</button>
<form method="post" id="sendDataForm" name="sendMsgForm" hidden>
<div class="mb-3">
<label for="sensorID" class="form-label">Sensor ID</label>
<input
type="text"
class="form-control"
name="sensorID"
id="sensorID"
required
maxlength="60"
value="0578E0"
/>
</div>
<button type="submit" class="btn btn-primary">Get Data</button>
</form>
<br />
<button class="btn btn-danger" id="clearScreen" disabled>
Clear screen
</button>
</div>
<div class="col-md-8">
<img src="air_quality_lcd.jpg" class="img-fluid" />
</div>
</div>
</div>
<script src="script.js"></script>
</body>
</html>
import * as my_dongle from 'bleuio'
import 'regenerator-runtime/runtime'
const dongleToConnect='[0]40:48:FD:E5:2F:17'
//const sensorID = '0578E0'
document.getElementById('connect').addEventListener('click', function(){
my_dongle.at_connect()
document.getElementById("clearScreen").disabled=false;
document.getElementById("connect").disabled=true;
document.getElementById("sendDataForm").hidden=false;
})
document.getElementById("sendDataForm").addEventListener("submit", function(event){
event.preventDefault()
const sensorID = document.getElementById('sensorID').value
getSensorData(sensorID)
setInterval(function () {getSensorData(sensorID)}, 10000);

});
const getSensorData =((sensorID)=>{
my_dongle.ati().then((data)=>{
//make central if not
if(JSON.stringify(data).includes("Peripheral")){
console.log('peripheral')
my_dongle.at_dual().then((x)=>{
console.log('central now')
})
}
})
.then(()=>{
// connect to dongle
my_dongle.at_getconn().then((y)=>{
if(JSON.stringify(y).includes(dongleToConnect)){
console.log('already connected')
}else{
my_dongle.at_gapconnect(dongleToConnect).then(()=>{
console.log('connected successfully')
})
}
})
.then(async()=>{
return my_dongle.at_findscandata(sensorID,6).then((sd)=>{
console.log('scandata',sd)
let advData = sd[sd.length - 1].split(" ").pop()
let positionOfID= advData.indexOf(sensorID);
let tempHex = advData.substring(positionOfID+14, positionOfID+18)
let temp = parseInt('0x'+tempHex.match(/../g).reverse().join(''))/10;
let co2Hex = advData.substring(positionOfID+38, positionOfID+42)
let co2 = parseInt('0x'+co2Hex);
//console.log(temp,co2)
return {
'CO2' :co2,
'Temp' :temp,
}
})
})
.then((x)=>{
console.log(x.CO2)
console.log(x.Temp)
var theVal = "L=1 SENSOR ID "+sensorID+" TEMPERATURE " + x.Temp + ' °c CO2 '+ x.CO2+' ppm';
console.log('Message Send 1 ')
// send command to show data
my_dongle.at_spssend(theVal).then(()=>{
console.log('Message Send '+theVal)
})
})

})
})
document.getElementById('clearScreen').addEventListener('click', function(){
my_dongle.ati().then((data)=>{
//make central if not
if(JSON.stringify(data).includes("Peripheral")){
console.log('peripheral')
my_dongle.at_central().then((x)=>{
console.log('central now')
})
}
})
.then(()=>{
// connect to dongle
my_dongle.at_getconn().then((y)=>{
if(JSON.stringify(y).includes(dongleToConnect)){
console.log('already connected')
}else{
my_dongle.at_gapconnect(dongleToConnect).then(()=>{
console.log('connected successfully')
})
}
})
.then(()=>{
// send command to clear the screen
my_dongle.at_spssend('L=0').then(()=>{
console.log('Screen Cleared')
})
})

})
})

Get the MAC address

- Open this site https://bleuio.com/web_terminal.html and click connect to dongle.
- Select the appropriate port to connect.
- Once it says connected, type ATI. This will show dongle information and current status.
- If the dongle is on peripheral role, set it to central by typing AT+CENTRAL
- Now do a gap scan by typing AT+GAPSCAN
- Once you see your dongle on the list ,stop the scan by pressing control+c
- Copy the ID and paste it into the script (script.js) line #4

Run the web script

Output

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Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store