Hello readers, I hope you are all doing great. Welcome to the 2nd lecture of Section 5(ESP32 Sensors) in the ESP32 Programming Series. In the previous tutorial, we discussed the built-in ESP32 Hall Effect Sensor. In this tutorial, we will discuss another inbuilt sensor of the ESP32 i.e. Capacitive Touch Sensor.
ESP32 Board has 10 built-in capacitive touch pins, which generate an electrical signal when someone touches these pins. These ESP32 touch pins are normally used to wake up the board from deep sleep mode. These touch pins are also used to replace the normal mechanical buttons with touch pads, improving the presentation of the IoT projects.
Here's the video demonstration of the ESP32 Capacitive Touch Sensor:
Before going forward, let's first understand how this touch sensor works:
| Where To Buy? | ||||
|---|---|---|---|---|
| No. | Components | Distributor | Link To Buy | |
| 1 | ESP32 | Amazon | Buy Now | |
Capacitance is determined by the geometry of the conductors and the dielectric materials used. Changing any of these factors will result in changing the capacitance.
C = Ad
As we know, the human body also carries a small electric charge. So, when a body approaches the metallic plates(of a capacitor), the mutual capacitance between the two metal plates decreases. This change in capacitance is used to detect the touch in these capacitive sensors.
So, if someone touches any of these pins, ESP32 can easily detect it. The pin mapping of touch-sensitive pins in DOIT ESP32 DevKit V1 with GPIO pins is shown below:
| ESP32 Capacitive Touch Pins | ||||
|---|---|---|---|---|
| No. | Parameter Name | Parameter Value | ||
| 1 |
Touch0 | GPIO4 | ||
| 2 |
Touch1 | GPIO0(not available in DOIT ESP32 Dev-kit V1 30-pin module but available in the 36-pin module) | ||
| 3 |
Touch2 | GPIO2 | ||
| 4 |
Touch3 | GPIO15 | ||
| 5 |
Touch4 | GPIO13 | ||
| 6 |
Touch5 | GPIO12 | ||
| 7 |
Touch6 | GPIO14 | ||
| 8 |
Touch7 | GPIO27 | ||
| 9 |
Touch8 | GPIO33 | ||
| 10 |
Touch9 | GPIO32 | ||
We are using the Arduino IDE development environment for programming ESP32. If you are new to Arduino IDE, read out How to Install ESP32 in Arduino IDE. Let's use the builtin Touch Sensor example in Arduino IDE:
In Arduino IDE there are two example codes available for the ESP32 touch sensor. We will discuss and implement both example codes in this tutorial. So, let's first open the TouchRead Code:
Here's the code for the TouchRead Example:
// ESP32 Touch Test
void setup()
{
Serial.begin(115200);
delay(1000); // give me time to bring up serial monitor
Serial.println("ESP32 Touch Test");
}
void loop()
{
Serial.println(touchRead(T0)); // get value using T0
delay(1000);
}Inside the setup() function, the serial monitor is initialized at a baud rate of 115200 to display the sensor readings. Finally, we printed the message(ESP32 Touch Test) on the Serial Monitor:
void setup()
{
Serial.begin(115200);
delay(1000); // give me time to bring up serial monitor
Serial.println("ESP32 Touch Test");
}void loop()
{
Serial.println(touchRead(T0)); // get value using T0
delay(1000);
}These capacitive touch sensor pins are mainly used to generate an external interrupt for waking up ESP32 from low power modes(deep sleep mode). Moreover, can also be used to control external peripherals like LED blinking or tuning on a DC motor, when a capacitive touch-interrupt is observed. So, let's have a look at How to Generate external interrupt by touching the ESP32 capacitive touch pins:
Here's the ESP32 Touch Interrupt Code:
const int CAPACITIVE_TOUCH_INPUT_PIN = T0; // GPIO pin 4
const int LED_OUTPUT_PIN = LED_BUILTIN;
const int TOUCH_THRESHOLD = 40; // turn on light if touchRead value < this threshold
volatile boolean _touchDetected = false;
void setup()
{
Serial.begin(115200);
pinMode(LED_OUTPUT_PIN, OUTPUT);
pinMode(LED_OUTPUT_PIN, LOW);
touchAttachInterrupt(CAPACITIVE_TOUCH_INPUT_PIN, touchDetected, TOUCH_THRESHOLD);
}
void touchDetected()
{
_touchDetected = true;
}
void loop()
{
if(_touchDetected)
{
Serial.println("Touch detected.");
_touchDetected = false;
Serial.println("blink the LED");
digitalWrite(LED_OUTPUT_PIN, HIGH);
delay(1000);
digitalWrite(LED_OUTPUT_PIN, LOW);
delay(1000);
}
}Let's understand the code by parts:
const int CAPACITIVE_TOUCH_INPUT_PIN = T0; // GPIO pin 4
const int LED_OUTPUT_PIN = LED_BUILTIN;
const int TOUCH_THRESHOLD = 40; // turn on light if touchRead value < this threshold
volatile boolean _touchDetected = false;void setup()
{
Serial.begin(115200);
pinMode(LED_OUTPUT_PIN, OUTPUT);
pinMode(LED_OUTPUT_PIN, LOW);
touchAttachInterrupt(CAPACITIVE_TOUCH_INPUT_PIN, touchDetected, TOUCH_THRESHOLD);
}void touchDetected()
{
_touchDetected = true;
}void loop()
{
if(_touchDetected)
{
Serial.println("Touch detected.");
_touchDetected = false;
Serial.println("blink the LED");
digitalWrite(LED_OUTPUT_PIN, HIGH);
delay(1000);
digitalWrite(LED_OUTPUT_PIN, LOW);
delay(1000);
}
}This concludes the tutorial; I hope you found this helpful and also hope to see you again with a new tutorial on ESP32.
Hello readers, I hope you all are doing great. Welcome to Section 5 of the ESP32 Programming Series. In this section, we are going to interface different Embedded Sensors with the ESP32 Microcontroller Board. ESP32 development board is featured with some inbuilt sensors(i.e. hall effect sensor, capacitive touch sensor) so, in the initial tutorials of this section, we will explore these built-in ESP32 sensors and in the later lectures, we will interface third-party sensors with the ESP32.
In today's lecture, we will discuss the working/operation of the ESP32 built-in Hall Effect Sensor. Hall Effect sensor is used to detect the variation in the magnetic field of its surroundings. So, let's first understand What's Hall Effect:
| Where To Buy? | ||||
|---|---|---|---|---|
| No. | Components | Distributor | Link To Buy | |
| 1 | ESP32 | Amazon | Buy Now | |
The Hall Effect phenomenon was first discovered by Edwin Hall in 1879. When current passes through a conductor, the electrons move in a straight line and thus the voltage difference across the conductor's surface remains zero, as shown in the below figure:
However, when a magnet is placed near the current-carrying conductor in a way that the direction of the magnetic field is perpendicular to the flow of current, the electrons get diverted and don't follow a straight line, which results in generating a small potential difference across the conductor's surface, as shown in the below figure:
This small potential difference generated because of magnetic field presence is called Hall Voltage. This magnetic field influence over the current-carrying conductor is termed the Hall Effect.
A Hall Effect Sensor is a non-contact type embedded sensor, used to detect the presence & intensity of a magnetic field in its surroundings. Different third-party Hall Effect Sensors available in the market are shown in the below figure:
In ESP32, the Hall effect sensor is located inside the ESP-WROOM-32 metallic cover. As the Hall Effect sensor is a non-contact type, it doesn't have to be in contact with the magnet. We just need to place the magnet above this metallic sheet and the ESP32 Hall Effect sensor will detect it.
To understand the working of the Hall sensor with ESP32, let's test the builtin ESP32 example:
Here's the code for this ESP32 Hall Sensor example:
int val = 0;
void setup()
{
Serial.begin (9600);
}
void loop()
{
val = hallRead();
Serial.print ("sensor value = ");
Serial.println (val);//to graph
delay(100);
}The code is quite simple, where the hallRead() function is called to read the hall sensor value, store it into a variable and then print it on the Serial monitor. Finally added a small delay to get the next value. Let me explain the code line by line for the beginners:
int val = 0;void setup()
{
Serial.begin (9600);
}void loop()
{
val = hallRead();
Serial.print ("sensor value = ");
Serial.println (val);//to graph
delay(100);
}This concludes the tutorial. I hope you found this helpful, test it out and if feel any difficulty, let me know in the comments. In the next tutorial, we will have a look at another built-in sensor of ESP32 i.e. Capacitive Touch Sensor. Thanks for reading.
Hello readers, I hope you are all doing great. In this tutorial, we are going to discuss the OTA web updater on the ESP32.
We already covered the fundamentals of OTA programming in ESP32, in our previous tutorial where we used the Arduino IDE to upload OTA code into the ESP32 module using the network port.
In the OTA web updater, you need to create a web server page for OTA programming.
Fig.1 ESP32 OTA web updater
| Where To Buy? | ||||
|---|---|---|---|---|
| No. | Components | Distributor | Link To Buy | |
| 1 | ESP32 | Amazon | Buy Now | |
Fig. 2
In this tutorial, we will discuss only the OTA web updater method using Arduino IDE and ESP32 dev-Kit V1 module.
If you want to know more about the basics of ESP32 and how to get started with Arduino IDE, then read Introduction to ESP32 Programming Series.
#include <WiFi.h> #include <WiFiClient.h> #include <WebServer.h> #include <ESPmDNS.h> #include <Update.h> const char* host = "esp32"; const char* ssid = "SSID"; const char* password = "password"; WebServer server(80); /* * Login page */ const char* loginIndex = "<form name='loginForm'>" "<table width='20%' bgcolor='A09F9F' align='center'>" "<tr>" "<td colspan=2>" "<center><font size=4><b>ESP32 Login Page</b></font></center>" "<br>" "</td>" "<br>" "<br>" "</tr>" "<td>Username:</td>" "<td><input type='text' size=25 name='userid'><br></td>" "</tr>" "<br>" "<br>" "<tr>" "<td>Password:</td>" "<td><input type='Password' size=25 name='pwd'><br></td>" "<br>" "<br>" "</tr>" "<tr>" "<td><input type='submit' onclick='check(this.form)' value='Login'></td>" "</tr>" "</table>" "</form>" "<script>" "function check(form)" "{" "if(form.userid.value=='admin' && form.pwd.value=='admin')" "{" "window.open('/serverIndex')" "}" "else" "{" " alert('Error Password or Username')/*displays error message*/" "}" "}" "</script>"; /* * Server Index Page */ const char* serverIndex = "<script src='https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js'></script>" "<form method='POST' action='#' enctype='multipart/form-data' id='upload_form'>" "<input type='file' name='update'>" "<input type='submit' value='Update'>" "</form>" "<div id='prg'>progress: 0%</div>" "<script>" "$('form').submit(function(e){" "e.preventDefault();" "var form = $('#upload_form')[0];" "var data = new FormData(form);" " $.ajax({" "url: '/update'," "type: 'POST'," "data: data," "contentType: false," "processData:false," "xhr: function() {" "var xhr = new window.XMLHttpRequest();" "xhr.upload.addEventListener('progress', function(evt) {" "if (evt.lengthComputable) {" "var per = evt.loaded / evt.total;" "$('#prg').html('progress: ' + Math.round(per*100) + '%');" "}" "}, false);" "return xhr;" "}," "success:function(d, s) {" "console.log('success!')" "}," "error: function (a, b, c) {" "}" "});" "});" "</script>"; /* * setup function */ void setup(void) { Serial.begin(115200); // Connect to WiFi network WiFi.begin(ssid, password); Serial.println(""); // Wait for connection while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); } Serial.println(""); Serial.print("Connected to "); Serial.println(ssid); Serial.print("IP address: "); Serial.println(WiFi.localIP()); /*use mdns for host name resolution*/ if (!MDNS.begin(host)) { //http://esp32.local Serial.println("Error setting up MDNS responder!"); while (1) { delay(1000); } } Serial.println("mDNS responder started"); server.on("/", HTTP_GET, []() { server.sendHeader("Connection", "close"); server.send(200, "text/html", loginIndex); }); server.on("/serverIndex", HTTP_GET, []() { server.sendHeader("Connection", "close"); server.send(200, "text/html", serverIndex); }); /*handling uploading firmware file */ server.on("/update", HTTP_POST, []() { server.sendHeader("Connection", "close"); server.send(200, "text/plain", (Update.hasError()) ? "FAIL" : "OK"); ESP.restart(); }, []() { HTTPUpload& upload = server.upload(); if (upload.status == UPLOAD_FILE_START) { Serial.printf("Update: %s\n", upload.filename.c_str()); if (!Update.begin(UPDATE_SIZE_UNKNOWN)) { //start with max available size Update.printError(Serial); } } else if (upload.status == UPLOAD_FILE_WRITE) { /* flashing firmware to ESP*/ if (Update.write(upload.buf, upload.currentSize) != upload.currentSize) { Update.printError(Serial); } } else if (upload.status == UPLOAD_FILE_END) { if (Update.end(true)) { //true to set the size to the current progress Serial.printf("Update Success: %u\nRebooting...\n", upload.totalSize); } else { Update.printError(Serial); } } }); server.begin(); } void loop(void) { server.handleClient(); delay(1); }
Fig. 4
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Fig. 9
Fig. 10
Fig. 12
Fig. 13
Fig. 14
Fig. 16
Fig. 17
#include <WiFi.h> #include <WiFiClient.h> #include <WebServer.h> #include <ESPmDNS.h> #include <Update.h> const char* host = "esp32"; const char* ssid = "SSID"; const char* password = "password"; //variabls to blink without delay: const int led = 2; unsigned long previousMillis = 0; // will store last time LED was updated const long interval = 1000; // interval at which to blink (milliseconds) int ledState = LOW; // ledState used to set the LED WebServer server(80); /* * Login page */ const char* loginIndex = "<form name='loginForm'>" "<table width='20%' bgcolor='A09F9F' align='center'>" "<tr>" "<td colspan=2>" "<center><font size=4><b>ESP32 Login Page</b></font></center>" "<br>" "</td>" "<br>" "<br>" "</tr>" "<td>Username:</td>" "<td><input type='text' size=25 name='userid'><br></td>" "</tr>" "<br>" "<br>" "<tr>" "<td>Password:</td>" "<td><input type='Password' size=25 name='pwd'><br></td>" "<br>" "<br>" "</tr>" "<tr>" "<td><input type='submit' onclick='check(this.form)' value='Login'></td>" "</tr>" "</table>" "</form>" "<script>" "function check(form)" "{" "if(form.userid.value=='admin' && form.pwd.value=='admin')" "{" "window.open('/serverIndex')" "}" "else" "{" " alert('Error Password or Username')/*displays error message*/" "}" "}" "</script>"; /* * Server Index Page */ const char* serverIndex = "<script src='https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js'></script>" "<form method='POST' action='#' enctype='multipart/form-data' id='upload_form'>" "<input type='file' name='update'>" "<input type='submit' value='Update'>" "</form>" "<div id='prg'>progress: 0%</div>" "<script>" "$('form').submit(function(e){" "e.preventDefault();" "var form = $('#upload_form')[0];" "var data = new FormData(form);" " $.ajax({" "url: '/update'," "type: 'POST'," "data: data," "contentType: false," "processData:false," "xhr: function() {" "var xhr = new window.XMLHttpRequest();" "xhr.upload.addEventListener('progress', function(evt) {" "if (evt.lengthComputable) {" "var per = evt.loaded / evt.total;" "$('#prg').html('progress: ' + Math.round(per*100) + '%');" "}" "}, false);" "return xhr;" "}," "success:function(d, s) {" "console.log('success!')" "}," "error: function (a, b, c) {" "}" "});" "});" "</script>"; /* * setup function */ void setup(void) { pinMode(led, OUTPUT); Serial.begin(115200); // Connect to WiFi network WiFi.begin(ssid, password); Serial.println(""); // Wait for connection while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); } Serial.println(""); Serial.print("Connected to "); Serial.println(ssid); Serial.print("IP address: "); Serial.println(WiFi.localIP()); /*use mdns for host name resolution*/ if (!MDNS.begin(host)) { //http://esp32.local Serial.println("Error setting up MDNS responder!"); while (1) { delay(1000); } } Serial.println("mDNS responder started"); /*return index page which is stored in serverIndex */ server.on("/", HTTP_GET, []() { server.sendHeader("Connection", "close"); server.send(200, "text/html", loginIndex); }); server.on("/serverIndex", HTTP_GET, []() { server.sendHeader("Connection", "close"); server.send(200, "text/html", serverIndex); }); /*handling uploading firmware file */ server.on("/update", HTTP_POST, []() { server.sendHeader("Connection", "close"); server.send(200, "text/plain", (Update.hasError()) ? "FAIL" : "OK"); ESP.restart(); }, []() { HTTPUpload& upload = server.upload(); if (upload.status == UPLOAD_FILE_START) { Serial.printf("Update: %s\n", upload.filename.c_str()); if (!Update.begin(UPDATE_SIZE_UNKNOWN)) { //start with max available size Update.printError(Serial); } } else if (upload.status == UPLOAD_FILE_WRITE) { /* flashing firmware to ESP*/ if (Update.write(upload.buf, upload.currentSize) != upload.currentSize) { Update.printError(Serial); } } else if (upload.status == UPLOAD_FILE_END) { if (Update.end(true)) { //true to set the size to the current progress Serial.printf("Update Success: %u\nRebooting...\n", upload.totalSize); } else { Update.printError(Serial); } } }); server.begin(); } void loop(void) { server.handleClient(); delay(1); //loop to blink without delay unsigned long currentMillis = millis(); if (currentMillis - previousMillis >= interval) { // save the last time you blinked the LED previousMillis = currentMillis; // if the LED is off turn it on and vice-versa: ledState = not(ledState); // set the LED with the ledState of the variable: digitalWrite(led, ledState); } }
Fig. 19
Fig. 20
Fig. 21 bin file
Fig. 23 LED blink
This concludes the tutorial. I hope, you found this helpful and I hope to see you soon for the new ESP32 tutorial.