Can you connect an esp8266 to an arduino mega board to give it internet connection ?
Yes, I can connect a Mega and an ESP8266 in such a way that the 2 devices communicate with each other AND have the ESP8266 communicate with a network, such as the internet.
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Can you show me your procedure ??
Google : connect Arduino 2560 to ESP8266
There are lots of examples on how to do this. When you have the basics, it is a fairly easy project.
As a point to remember, the ESP8266 series of boards are 3.3V, and you would use either a logic level converter, or 2 resistors to convert the 5V signal to a 3.3V one.
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What Ohm resistors should I use
Hi, @kalaca
Welcome to the forum.
Can you tell us what your project is please?
Can you please tell us your electronics, programming, arduino, hardware experience?
Tom... 
Thanks to @missdrew for the suggestion. I was going to reply in a similar fashion.
A logic level shifter:
I no longer allow the 12 ESP32's access to the internet. Instead the ESP32's connect to a RPi (Raspberry Pi 4) MQTT Broker. The RPi does the internet thing for the ESP32's.
/*
Chappie Weather upgrade/addition
process wind speed direction and rain fall.
*/
#include <WiFi.h>
#include <PubSubClient.h>
#include "certs.h"
#include "sdkconfig.h"
#include "esp_system.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/timers.h"
#include "freertos/event_groups.h"
#include "driver/pcnt.h"
#include <driver/adc.h>
#include <SimpleKalmanFilter.h>
#include <ESP32Time.h>
////
ESP32Time rtc;
WiFiClient wifiClient;
PubSubClient MQTTclient(mqtt_server, mqtt_port, wifiClient);
////
float CalculatedVoltage = 0.0f;
float kph = 0.0f;
float rain = 0.0f;
/*
PCNT PCNT_UNIT_0, PCNT_CHANNEL_0 GPIO_NUM_15 = pulse input pin
PCNT PCNT_UNIT_1, PCNT_CHANNEL_0 GPIO_NUM_4 = pulse input pin
*/
pcnt_unit_t pcnt_unit00 = PCNT_UNIT_0; //pcnt unit 0 channel 0
pcnt_unit_t pcnt_unit10 = PCNT_UNIT_1; //pcnt unit 1 channel 0
//
//
hw_timer_t * timer = NULL;
//
#define evtAnemometer ( 1 << 0 )
#define evtRainFall ( 1 << 1 )
#define evtParseMQTT ( 1 << 2 )
EventGroupHandle_t eg;
#define OneMinuteGroup ( evtAnemometer | evtRainFall )
////
QueueHandle_t xQ_Message; // payload and topic queue of MQTT payload and topic
const int payloadSize = 100;
struct stu_message
{
char payload [payloadSize] = {'\0'};
String topic ;
} x_message;
////
SemaphoreHandle_t sema_MQTT_KeepAlive;
SemaphoreHandle_t sema_mqttOK;
SemaphoreHandle_t sema_CalculatedVoltage;
////
int mqttOK = 0; // stores a count value that is used to cause an esp reset
volatile bool TimeSet = false;
////
/*
A single subject has been subscribed to, the mqtt broker sends out "OK" messages if the client receives an OK message the mqttOK value is set back to zero.
*/
////
void IRAM_ATTR mqttCallback(char* topic, byte * payload, unsigned int length)
{
memset( x_message.payload, '\0', payloadSize ); // clear payload char buffer
x_message.topic = ""; //clear topic string buffer
x_message.topic = topic; //store new topic
int i = 0; // extract payload
for ( i; i < length; i++)
{
x_message.payload[i] = ((char)payload[i]);
}
x_message.payload[i] = '\0';
xQueueOverwrite( xQ_Message, (void *) &x_message );// send data to queue
} // void mqttCallback(char* topic, byte* payload, unsigned int length)
////
// interrupt service routine for WiFi events put into IRAM
void IRAM_ATTR WiFiEvent(WiFiEvent_t event)
{
switch (event) {
case SYSTEM_EVENT_STA_CONNECTED:
break;
case SYSTEM_EVENT_STA_DISCONNECTED:
log_i("Disconnected from WiFi access point");
break;
case SYSTEM_EVENT_AP_STADISCONNECTED:
log_i("WiFi client disconnected");
break;
default: break;
}
} // void IRAM_ATTR WiFiEvent(WiFiEvent_t event)
////
void IRAM_ATTR onTimer()
{
BaseType_t xHigherPriorityTaskWoken;
xEventGroupSetBitsFromISR(eg, OneMinuteGroup, &xHigherPriorityTaskWoken);
} // void IRAM_ATTR onTimer()
////
void setup()
{
eg = xEventGroupCreate(); // get an event group handle
// x_message.topic.reserve(300);
adc1_config_width(ADC_WIDTH_12Bit);
adc1_config_channel_atten(ADC1_CHANNEL_6, ADC_ATTEN_DB_11);// using GPIO 34 wind direction
adc1_config_channel_atten(ADC1_CHANNEL_3, ADC_ATTEN_DB_11);// using GPIO 39 current
adc1_config_channel_atten(ADC1_CHANNEL_0, ADC_ATTEN_DB_11);// using GPIO 36 battery volts
// hardware timer 4 set for one minute alarm
timer = timerBegin( 3, 80, true );
timerAttachInterrupt( timer, &onTimer, true );
timerAlarmWrite(timer, 60000000, true);
timerAlarmEnable(timer);
/* Initialize PCNT's counter */
int PCNT_H_LIM_VAL = 3000;
int PCNT_L_LIM_VAL = -10;
// 1st PCNT counter
pcnt_config_t pcnt_config = {};
pcnt_config.pulse_gpio_num = GPIO_NUM_15;// Set PCNT input signal and control GPIOs
pcnt_config.ctrl_gpio_num = PCNT_PIN_NOT_USED;
pcnt_config.channel = PCNT_CHANNEL_0;
pcnt_config.unit = PCNT_UNIT_0;
// What to do on the positive / negative edge of pulse input?
pcnt_config.pos_mode = PCNT_COUNT_INC; // Count up on the positive edge
pcnt_config.neg_mode = PCNT_COUNT_DIS; // Count down disable
// What to do when control input is low or high?
pcnt_config.lctrl_mode = PCNT_MODE_KEEP; // do not count if low reverse
pcnt_config.hctrl_mode = PCNT_MODE_KEEP; // Keep the primary counter mode if high
// Set the maximum and minimum limit values to watch
pcnt_config.counter_h_lim = PCNT_H_LIM_VAL;
pcnt_config.counter_l_lim = PCNT_L_LIM_VAL;
pcnt_unit_config(&pcnt_config); // Initialize PCNT unit
pcnt_set_filter_value( PCNT_UNIT_0, 1); //Configure and enable the input filter
pcnt_filter_enable( PCNT_UNIT_0 );
pcnt_counter_pause( PCNT_UNIT_0 );
pcnt_counter_clear( PCNT_UNIT_0 );
pcnt_counter_resume( PCNT_UNIT_0); // start the show
// setup 2nd PCNT
pcnt_config = {};
pcnt_config.pulse_gpio_num = GPIO_NUM_4;
pcnt_config.ctrl_gpio_num = PCNT_PIN_NOT_USED;
pcnt_config.channel = PCNT_CHANNEL_0;
pcnt_config.unit = PCNT_UNIT_1;
pcnt_config.pos_mode = PCNT_COUNT_INC;
pcnt_config.neg_mode = PCNT_COUNT_DIS;
pcnt_config.lctrl_mode = PCNT_MODE_KEEP;
pcnt_config.hctrl_mode = PCNT_MODE_KEEP;
pcnt_config.counter_h_lim = PCNT_H_LIM_VAL;
pcnt_config.counter_l_lim = PCNT_L_LIM_VAL;
pcnt_unit_config(&pcnt_config);
//pcnt_set_filter_value( PCNT_UNIT_1, 1 );
//pcnt_filter_enable ( PCNT_UNIT_1 );
pcnt_counter_pause ( PCNT_UNIT_1 );
pcnt_counter_clear ( PCNT_UNIT_1 );
pcnt_counter_resume ( PCNT_UNIT_1 );
//
xQ_Message = xQueueCreate( 1, sizeof(stu_message) );
//
sema_CalculatedVoltage = xSemaphoreCreateBinary();
xSemaphoreGive( sema_CalculatedVoltage );
sema_mqttOK = xSemaphoreCreateBinary();
xSemaphoreGive( sema_mqttOK );
sema_MQTT_KeepAlive = xSemaphoreCreateBinary();
///
xTaskCreatePinnedToCore( MQTTkeepalive, "MQTTkeepalive", 15000, NULL, 5, NULL, 1 );
xTaskCreatePinnedToCore( fparseMQTT, "fparseMQTT", 10000, NULL, 5, NULL, 1 ); // assign all to core 1, WiFi in use.
xTaskCreatePinnedToCore( fReadBattery, "fReadBattery", 4000, NULL, 3, NULL, 1 );
xTaskCreatePinnedToCore( fReadCurrent, "fReadCurrent", 4000, NULL, 3, NULL, 1 );
xTaskCreatePinnedToCore( fWindDirection, "fWindDirection", 10000, NULL, 4, NULL, 1 );
xTaskCreatePinnedToCore( fAnemometer, "fAnemometer", 10000, NULL, 4, NULL, 1 );
xTaskCreatePinnedToCore( fRainFall, "fRainFall", 10000, NULL, 4, NULL, 1 );
xTaskCreatePinnedToCore( fmqttWatchDog, "fmqttWatchDog", 3000, NULL, 3, NULL, 1 ); // assign all to core 1
} //void setup()
////
void fWindDirection( void *pvParameters )
// read the wind direction sensor, return heading in degrees
{
float adcValue = 0.0f;
uint64_t TimePastKalman = esp_timer_get_time();
SimpleKalmanFilter KF_ADC( 1.0f, 1.0f, .01f );
float high = 0.0f;
float low = 2000.0f;
float ADscale = 3.3f / 4096.0f;
TickType_t xLastWakeTime = xTaskGetTickCount();
const TickType_t xFrequency = 100; //delay for mS
int count = 0;
String windDirection;
windDirection.reserve(20);
String MQTTinfo = "";
MQTTinfo.reserve( 150 );
while ( !MQTTclient.connected() )
{
vTaskDelay( 250 );
}
for (;;)
{
windDirection = "";
adcValue = float( adc1_get_raw(ADC1_CHANNEL_6) ); //take a raw ADC reading
KF_ADC.setProcessNoise( (esp_timer_get_time() - TimePastKalman) / 1000000.0f ); //get time, in microsecods, since last readings
adcValue = KF_ADC.updateEstimate( adcValue ); // apply simple Kalman filter
TimePastKalman = esp_timer_get_time(); // time of update complete
adcValue = adcValue * ADscale;
log_i( " adc %f", adcValue );
if ( (adcValue >= 0.0f) & (adcValue <= .25f ) )
{
// log_i( " n" );
windDirection.concat( "N" );
}
//
// if ( (adcValue >= .25f) & adcValue <= .5f )
// {
// log_i( " nne" );
// windDirection.concat( "NNE");
// }
//
if ( (adcValue > .25f) & (adcValue <= .6f ) )
{
// log_i( " e" );
windDirection.concat( "E" );
}
// if ( (adcValue > 1.0f) & (adcValue < 1.75f) )
// {
// log_i( " sse" );
// windDirection.concat( "S-SE");
// }
// //
// if ( (adcValue >= 1.75f) & (adcValue < 2.2f) )
// {
// log_i( " nnw" );
// windDirection.concat( "N-NW" );
// }
//
if ( (adcValue > 2.0f) & ( adcValue < 3.3f) )
{
// log_i( " s" );
windDirection.concat( "S");
}
//
// if ( (adcValue > 2.6f) & (adcValue < 3.0f ) )
// {
// log_i( " ssw" );
// windDirection.concat( "S-SW" );
// }
if ( (adcValue >= 1.7f) & (adcValue < 2.0f ) )
{
// log_i( " w" );
windDirection.concat( "W" );
}
if( count >= 30 )
{
MQTTinfo.concat( String(kph, 2) );
MQTTinfo.concat( ",");
MQTTinfo.concat( windDirection );
MQTTinfo.concat( ",");
MQTTinfo.concat( String(rain,2) );
xSemaphoreTake( sema_MQTT_KeepAlive, portMAX_DELAY );
MQTTclient.publish( topicWSWDRF, MQTTinfo.c_str() );
xSemaphoreGive( sema_MQTT_KeepAlive );
count = 0;
}
count++;
MQTTinfo = "";
xLastWakeTime = xTaskGetTickCount();
vTaskDelayUntil( &xLastWakeTime, xFrequency );
}
vTaskDelete ( NULL );
}
// read rainfall
void fRainFall( void *pvParemeters )
{
int16_t count = 0;
pcnt_counter_pause( PCNT_UNIT_1 );
pcnt_counter_clear( PCNT_UNIT_1 );
pcnt_counter_resume( PCNT_UNIT_1 );
for (;; )
{
xEventGroupWaitBits (eg, evtRainFall, pdTRUE, pdTRUE, portMAX_DELAY);
pcnt_counter_pause( PCNT_UNIT_1 );
pcnt_get_counter_value( PCNT_UNIT_1, &count );
pcnt_counter_clear( PCNT_UNIT_1 );
pcnt_counter_resume( PCNT_UNIT_1 );
if ( count != 0 )
{
// 0.2794mm of rain per click clear clicks at mid night
rain = 0.2794f * (float)count;
log_i( "count %d, rain rain = %f mm", count, rain );
}
}
vTaskDelete ( NULL );
}
////
void fAnemometer( void *pvParameters )
{
int16_t count = 0;
pcnt_counter_clear(PCNT_UNIT_0);
pcnt_counter_resume(PCNT_UNIT_0);
for (;;)
{
xEventGroupWaitBits (eg, evtAnemometer, pdTRUE, pdTRUE, portMAX_DELAY);
pcnt_counter_pause( PCNT_UNIT_0 );
pcnt_get_counter_value( PCNT_UNIT_0, &count); //int16_t *count
// A wind speed of 2.4km/h causes the switch to close once per second
kph = 2.4 * ((float)count / 60.0f);
//if ( count != 0 )
//{
log_i( "count %d, wind Kph = %f", count, kph );
//}
count = 0;
pcnt_counter_clear( PCNT_UNIT_0 );
pcnt_counter_resume( PCNT_UNIT_0 );
}
vTaskDelete ( NULL );
}
//////
void fmqttWatchDog( void * paramater )
{
int UpdateImeTrigger = 86400; //seconds in a day
int UpdateTimeInterval = 86300; // 1st time update in 100 counts
int maxNonMQTTresponse = 60;
for (;;)
{
vTaskDelay( 1000 );
if ( mqttOK >= maxNonMQTTresponse )
{
ESP.restart();
}
xSemaphoreTake( sema_mqttOK, portMAX_DELAY );
mqttOK++;
xSemaphoreGive( sema_mqttOK );
UpdateTimeInterval++; // trigger new time get
if ( UpdateTimeInterval >= UpdateImeTrigger )
{
TimeSet = false; // sets doneTime to false to get an updated time after a days count of seconds
UpdateTimeInterval = 0;
}
}
vTaskDelete( NULL );
}
//////
void fparseMQTT( void *pvParameters )
{
struct stu_message px_message;
for (;;)
{
if ( xQueueReceive(xQ_Message, &px_message, portMAX_DELAY) == pdTRUE )
{
// parse the time from the OK message and update MCU time
if ( String(px_message.topic) == topicOK )
{
if ( !TimeSet)
{
String temp = "";
temp = px_message.payload[0];
temp += px_message.payload[1];
temp += px_message.payload[2];
temp += px_message.payload[3];
int year = temp.toInt();
temp = "";
temp = px_message.payload[5];
temp += px_message.payload[6];
int month = temp.toInt();
temp = "";
temp = px_message.payload[8];
temp += px_message.payload[9];
int day = temp.toInt();
temp = "";
temp = px_message.payload[11];
temp += px_message.payload[12];
int hour = temp.toInt();
temp = "";
temp = px_message.payload[14];
temp += px_message.payload[15];
int min = temp.toInt();
rtc.setTime( 0, min, hour, day, month, year );
log_i( "rtc %s ", rtc.getTime() );
TimeSet = true;
}
}
//
} //if ( xQueueReceive(xQ_Message, &px_message, portMAX_DELAY) == pdTRUE )
xSemaphoreTake( sema_mqttOK, portMAX_DELAY );
mqttOK = 0;
xSemaphoreGive( sema_mqttOK );
}
} // void fparseMQTT( void *pvParameters )
//////
void fReadCurrent( void * parameter )
{
float ADbits = 4096.0f;
float ref_voltage = 3.3f;
float offSET = .0f;
uint64_t TimePastKalman = esp_timer_get_time(); // used by the Kalman filter UpdateProcessNoise, time since last kalman calculation
SimpleKalmanFilter KF_I( 1.0f, 1.0f, .01f );
float mA = 0.0f;
int printCount = 0;
const float mVperAmp = 100.0f;
float adcValue = 0;
float Voltage = 0;
float Power = 0.0;
String powerInfo = "";
powerInfo.reserve( 150 );
while ( !MQTTclient.connected() )
{
vTaskDelay( 250 );
}
TickType_t xLastWakeTime = xTaskGetTickCount();
const TickType_t xFrequency = 1000; //delay for mS
for (;;)
{
adc1_get_raw(ADC1_CHANNEL_3); // read once discard reading
adcValue = ( (float)adc1_get_raw(ADC1_CHANNEL_3) );
Voltage = ( (adcValue * ref_voltage) / ADbits ) + offSET; // Gets you mV
mA = Voltage / mVperAmp; // get amps
KF_I.setProcessNoise( (esp_timer_get_time() - TimePastKalman) / 1000000.0f ); //get time, in microsecods, since last readings
mA = KF_I.updateEstimate( mA ); // apply simple Kalman filter
TimePastKalman = esp_timer_get_time(); // time of update complete
printCount++;
if ( printCount == 60 )
{
xSemaphoreTake( sema_CalculatedVoltage, portMAX_DELAY);
Power = CalculatedVoltage * mA;
log_i( "Voltage=%f mA=%f Power=%f", CalculatedVoltage, mA, Power );
printCount = 0;
powerInfo.concat( String(CalculatedVoltage, 2) );
xSemaphoreGive( sema_CalculatedVoltage );
powerInfo.concat( ",");
powerInfo.concat( String(mA, 2) );
powerInfo.concat( ",");
powerInfo.concat( String(Power, 4) );
xSemaphoreTake( sema_MQTT_KeepAlive, portMAX_DELAY );
MQTTclient.publish( topicPower, powerInfo.c_str() );
xSemaphoreGive( sema_MQTT_KeepAlive );
powerInfo = "";
}
xLastWakeTime = xTaskGetTickCount();
vTaskDelayUntil( &xLastWakeTime, xFrequency );
}
vTaskDelete( NULL );
} //void fReadCurrent( void * parameter )
////
void fReadBattery( void * parameter )
{
//float ADbits = 4096.0f;
//float ref_voltage = 3.3f;
float ADscale = 3.3f / 4096.0f;
float adcValue = 0.0f;
float offSET = 0.0f;
const float r1 = 50500.0f; // R1 in ohm, 50K
const float r2 = 10000.0f; // R2 in ohm, 10k potentiometer
//float Vscale = (r1+r2)/r2;
float Vbatt = 0.0f;
int printCount = 0;
float vRefScale = (3.3f / 4096.0f) * ((r1 + r2) / r2);
uint64_t TimePastKalman = esp_timer_get_time(); // used by the Kalman filter UpdateProcessNoise, time since last kalman calculation
SimpleKalmanFilter KF_ADC_b( 1.0f, 1.0f, .01f );
TickType_t xLastWakeTime = xTaskGetTickCount();
const TickType_t xFrequency = 1000; //delay for mS
for (;;)
{
adc1_get_raw(ADC1_CHANNEL_0); //read and discard
adcValue = float( adc1_get_raw(ADC1_CHANNEL_0) ); //take a raw ADC reading
KF_ADC_b.setProcessNoise( (esp_timer_get_time() - TimePastKalman) / 1000000.0f ); //get time, in microsecods, since last readings
adcValue = KF_ADC_b.updateEstimate( adcValue ); // apply simple Kalman filter
Vbatt = adcValue * vRefScale;
xSemaphoreTake( sema_CalculatedVoltage, portMAX_DELAY );
CalculatedVoltage = Vbatt;
xSemaphoreGive( sema_CalculatedVoltage );
// printCount++;
// if ( printCount == 3 )
// {
// log_i( "Vbatt %f", Vbatt );
// printCount = 0;
// }
TimePastKalman = esp_timer_get_time(); // time of update complete
xLastWakeTime = xTaskGetTickCount();
vTaskDelayUntil( &xLastWakeTime, xFrequency );
//log_i( "fReadBattery %d", uxTaskGetStackHighWaterMark( NULL ) );
}
vTaskDelete( NULL );
}////
void MQTTkeepalive( void *pvParameters )
{
sema_MQTT_KeepAlive = xSemaphoreCreateBinary();
xSemaphoreGive( sema_MQTT_KeepAlive ); // found keep alive can mess with a publish, stop keep alive during publish
// setting must be set before a mqtt connection is made
MQTTclient.setKeepAlive( 90 ); // setting keep alive to 90 seconds makes for a very reliable connection, must be set before the 1st connection is made.
for (;;)
{
//check for a is-connected and if the WiFi 'thinks' its connected, found checking on both is more realible than just a single check
if ( (wifiClient.connected()) && (WiFi.status() == WL_CONNECTED) )
{
xSemaphoreTake( sema_MQTT_KeepAlive, portMAX_DELAY ); // whiles MQTTlient.loop() is running no other mqtt operations should be in process
MQTTclient.loop();
xSemaphoreGive( sema_MQTT_KeepAlive );
}
else {
log_i( "MQTT keep alive found MQTT status %s WiFi status %s", String(wifiClient.connected()), String(WiFi.status()) );
if ( !(wifiClient.connected()) || !(WiFi.status() == WL_CONNECTED) )
{
connectToWiFi();
}
connectToMQTT();
}
vTaskDelay( 250 ); //task runs approx every 250 mS
}
vTaskDelete ( NULL );
}
////
void connectToWiFi()
{
int TryCount = 0;
//log_i( "connect to wifi" );
while ( WiFi.status() != WL_CONNECTED )
{
TryCount++;
WiFi.disconnect();
WiFi.begin( SSID, PASSWORD );
vTaskDelay( 4000 );
if ( TryCount == 10 )
{
ESP.restart();
}
}
WiFi.onEvent( WiFiEvent );
} // void connectToWiFi()
////
void connectToMQTT()
{
MQTTclient.setKeepAlive( 90 ); // needs be made before connecting
byte mac[5];
WiFi.macAddress(mac);
String clientID = String(mac[0]) + String(mac[4]) ; // use mac address to create clientID
while ( !MQTTclient.connected() )
{
// boolean connect(const char* id, const char* user, const char* pass, const char* willTopic, uint8_t willQos, boolean willRetain, const char* willMessage);
MQTTclient.connect( clientID.c_str(), mqtt_username, mqtt_password, NULL , 1, true, NULL );
vTaskDelay( 250 );
}
MQTTclient.setCallback( mqttCallback );
MQTTclient.subscribe( topicOK );
} // void connectToMQTT()
////
void loop() {}
FWIW, some code used to connect a ESP32 to a MQTT Broker on a RPi.
Iv made connections with four stepper motors , a timing belt and a pulley to hold an object
I also have sensors
The movement depends on the sensor value and the esp8266 does not have enough pins for to support the motors
So I connected them to an arduino
But I want to view my sensor reading on my flutter app
I have an esp8266 here and I wanted to know how I would connect it to the mega to hv internet access
The words "connect mega to esp8266" in your internet search did not produce any results?
Making it unnecessarily hard for yourself. 
Just use a "port expander" to connect the ESP to your other devices.
This avoids having code on two different devices and figuring out how to get them to "talk" to each other.
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