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Added ESPNow basic example (espressif#667)
* Added ESPNow basic example * fixed meta doc for slave * refactored folder structure
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‎libraries/ESP32/examples/ESPNow/Basic/Master/Master.ino‎

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/**
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ESPNOW - Basic communication - Master
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Date: 26th September 2017
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Author: Arvind Ravulavaru <https://github.com/arvindr21>
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Purpose: ESPNow Communication between a Master ESP32 and a Slave ESP32
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Description: This sketch consists of the code for the Master module.
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Resources: (A bit outdated)
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a. https://espressif.com/sites/default/files/documentation/esp-now_user_guide_en.pdf
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b. http://www.esploradores.com/practica-6-conexion-esp-now/
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<< This Device Master >>
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Flow: Master
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Step 1 : ESPNow Init on Master and set it in STA mode
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Step 2 : Start scanning for Slave ESP32 (we have added a prefix of `slave` to the SSID of slave for an easy setup)
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Step 3 : Once found, add Slave as peer
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Step 4 : Register for send callback
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Step 5 : Start Transmitting data from Master to Slave
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Flow: Slave
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Step 1 : ESPNow Init on Slave
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Step 2 : Update the SSID of Slave with a prefix of `slave`
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Step 3 : Set Slave in AP mode
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Step 4 : Register for receive callback and wait for data
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Step 5 : Once data arrives, print it in the serial monitor
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Note: Master and Slave have been defined to easily understand the setup.
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Based on the ESPNOW API, there is no concept of Master and Slave.
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Any devices can act as master or salve.
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*/
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#include <esp_now.h>
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#include <WiFi.h>
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// Global copy of slave
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esp_now_peer_info_t slave;
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#define CHANNEL 3
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#define PRINTSCANRESULTS 0
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#define DELETEBEFOREPAIR 0
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// Init ESP Now with fallback
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void InitESPNow() {
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if (esp_now_init() == ESP_OK) {
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Serial.println("ESPNow Init Success");
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}
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else {
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Serial.println("ESPNow Init Failed");
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// Retry InitESPNow, add a counte and then restart?
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// InitESPNow();
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// or Simply Restart
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ESP.restart();
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}
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}
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// Scan for slaves in AP mode
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void ScanForSlave() {
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int8_t scanResults = WiFi.scanNetworks();
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bool slaveFound = 0;
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Serial.println("");
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if (scanResults == 0) {
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Serial.println("No WiFi devices in AP Mode found");
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} else {
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Serial.print("Found "); Serial.print(scanResults); Serial.println(" devices ");
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for (int i = 0; i < scanResults; ++i) {
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// Print SSID and RSSI for each device found
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String SSID = WiFi.SSID(i);
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int32_t RSSI = WiFi.RSSI(i);
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String BSSIDstr = WiFi.BSSIDstr(i);
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if (PRINTSCANRESULTS) {
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Serial.print(i + 1);
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Serial.print(": ");
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Serial.print(SSID);
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Serial.print(" (");
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Serial.print(RSSI);
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Serial.print(")");
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Serial.println("");
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}
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delay(10);
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// Check if the current device starts with `Slave`
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if (SSID.indexOf("Slave") == 0) {
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// SSID of interest
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Serial.println("Found a Slave.");
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Serial.print(i + 1); Serial.print(": "); Serial.print(SSID); Serial.print(" ["); Serial.print(BSSIDstr); Serial.print("]"); Serial.print(" ("); Serial.print(RSSI); Serial.print(")"); Serial.println("");
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// Get BSSID => Mac Address of the Slave
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int mac[6];
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if ( 6 == sscanf(BSSIDstr.c_str(), "%x:%x:%x:%x:%x:%x%c", &mac[0], &mac[1], &mac[2], &mac[3], &mac[4], &mac[5] ) ) {
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for (int ii = 0; ii < 6; ++ii ) {
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slave.peer_addr[ii] = (uint8_t) mac[ii];
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}
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}
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slave.channel = CHANNEL; // pick a channel
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slave.encrypt = 0; // no encryption
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slaveFound = 1;
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// we are planning to have only one slave in this example;
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// Hence, break after we find one, to be a bit efficient
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break;
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}
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}
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}
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if (slaveFound) {
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Serial.println("Slave Found, processing..");
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} else {
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Serial.println("Slave Not Found, trying again.");
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}
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// clean up ram
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WiFi.scanDelete();
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}
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// Check if the slave is already paired with the master.
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// If not, pair the slave with master
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bool manageSlave() {
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if (slave.channel == CHANNEL) {
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if (DELETEBEFOREPAIR) {
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deletePeer();
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}
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Serial.print("Slave Status: ");
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const esp_now_peer_info_t *peer = &slave;
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const uint8_t *peer_addr = slave.peer_addr;
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// check if the peer exists
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bool exists = esp_now_is_peer_exist(peer_addr);
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if ( exists) {
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// Slave already paired.
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Serial.println("Already Paired");
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return true;
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} else if (exists == ESP_ERR_ESPNOW_NOT_INIT) {
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// How did we get so far!!
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Serial.println("ESPNOW Not InitESP_ERR_ESPNOW_NOT_INIT");
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return false;
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} else if (exists == ESP_ERR_ESPNOW_ARG) {
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// Invalid Argument
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Serial.println("Invalid Argument");
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return false;
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} else {
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// Slave not paired, attempt pair
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esp_err_t addStatus = esp_now_add_peer(peer);
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if (addStatus == ESP_OK) {
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// Pair success
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Serial.println("Pair success");
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return true;
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} else if (addStatus == ESP_ERR_ESPNOW_NOT_INIT) {
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// How did we get so far!!
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Serial.println("ESPNOW Not Init");
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return false;
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} else if (addStatus == ESP_ERR_ESPNOW_ARG) {
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Serial.println("Invalid Argument");
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return false;
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} else if (addStatus == ESP_ERR_ESPNOW_FULL) {
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Serial.println("Peer list full");
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return false;
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} else if (addStatus == ESP_ERR_ESPNOW_NO_MEM) {
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Serial.println("Out of memory");
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return false;
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} else if (addStatus == ESP_ERR_ESPNOW_EXIST) {
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Serial.println("Peer Exists");
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return true;
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} else {
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Serial.println("Not sure what happened");
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return false;
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}
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}
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} else {
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// No slave found to process
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Serial.println("No Slave found to process");
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return false;
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}
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}
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void deletePeer() {
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const esp_now_peer_info_t *peer = &slave;
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const uint8_t *peer_addr = slave.peer_addr;
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esp_err_t delStatus = esp_now_del_peer(peer_addr);
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Serial.print("Slave Delete Status: ");
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if (delStatus == ESP_OK) {
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// Delete success
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Serial.println("Success");
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} else if (delStatus == ESP_ERR_ESPNOW_NOT_INIT) {
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// How did we get so far!!
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Serial.println("ESPNOW Not Init");
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} else if (delStatus == ESP_ERR_ESPNOW_ARG) {
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Serial.println("Invalid Argument");
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} else if (delStatus == ESP_ERR_ESPNOW_NOT_FOUND) {
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Serial.println("Peer not found.");
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} else {
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Serial.println("Not sure what happened");
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}
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}
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uint8_t data = 0;
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// send data
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void sendData() {
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data++;
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const uint8_t *peer_addr = slave.peer_addr;
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Serial.print("Sending: "); Serial.println(data);
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esp_err_t result = esp_now_send(peer_addr, &data, sizeof(data));
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Serial.print("Send Status: ");
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if (result == ESP_OK) {
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Serial.println("Success");
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} else if (result == ESP_ERR_ESPNOW_NOT_INIT) {
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// How did we get so far!!
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Serial.println("ESPNOW not Init.");
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} else if (result == ESP_ERR_ESPNOW_ARG) {
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Serial.println("Invalid Argument");
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} else if (result == ESP_ERR_ESPNOW_INTERNAL) {
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Serial.println("Internal Error");
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} else if (result == ESP_ERR_ESPNOW_NO_MEM) {
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Serial.println("ESP_ERR_ESPNOW_NO_MEM");
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} else if (result == ESP_ERR_ESPNOW_NOT_FOUND) {
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Serial.println("Peer not found.");
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} else {
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Serial.println("Not sure what happened");
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}
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}
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// callback when data is sent from Master to Slave
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void OnDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) {
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char macStr[18];
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snprintf(macStr, sizeof(macStr), "%02x:%02x:%02x:%02x:%02x:%02x",
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mac_addr[0], mac_addr[1], mac_addr[2], mac_addr[3], mac_addr[4], mac_addr[5]);
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Serial.print("Last Packet Sent to: "); Serial.println(macStr);
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Serial.print("Last Packet Send Status: "); Serial.println(status == ESP_NOW_SEND_SUCCESS ? "Delivery Success" : "Delivery Fail");
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}
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void setup() {
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Serial.begin(115200);
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//Set device in STA mode to begin with
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WiFi.mode(WIFI_STA);
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Serial.println("ESPNow/Basic/Master Example");
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// This is the mac address of the Master in Station Mode
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Serial.print("STA MAC: "); Serial.println(WiFi.macAddress());
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// Init ESPNow with a fallback logic
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InitESPNow();
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// Once ESPNow is successfully Init, we will register for Send CB to
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// get the status of Trasnmitted packet
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esp_now_register_send_cb(OnDataSent);
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}
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void loop() {
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// In the loop we scan for slave
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ScanForSlave();
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// If Slave is found, it would be populate in `slave` variable
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// We will check if `slave` is defined and then we proceed further
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if (slave.channel == CHANNEL) { // check if slave channel is defined
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// `slave` is defined
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// Add slave as peer if it has not been added already
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bool isPaired = manageSlave();
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if (isPaired) {
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// pair success or already paired
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// Send data to device
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sendData();
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} else {
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// slave pair failed
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Serial.println("Slave pair failed!");
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}
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}
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else {
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// No slave found to process
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}
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// wait for 3seconds to run the logic again
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delay(3000);
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}

‎libraries/ESP32/examples/ESPNow/Basic/Slave/Slave.ino‎

Lines changed: 90 additions & 0 deletions
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/**
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ESPNOW - Basic communication - Slave
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Date: 26th September 2017
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Author: Arvind Ravulavaru <https://github.com/arvindr21>
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Purpose: ESPNow Communication between a Master ESP32 and a Slave ESP32
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Description: This sketch consists of the code for the Slave module.
7+
Resources: (A bit outdated)
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a. https://espressif.com/sites/default/files/documentation/esp-now_user_guide_en.pdf
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b. http://www.esploradores.com/practica-6-conexion-esp-now/
10+
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<< This Device Slave >>
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Flow: Master
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Step 1 : ESPNow Init on Master and set it in STA mode
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Step 2 : Start scanning for Slave ESP32 (we have added a prefix of `slave` to the SSID of slave for an easy setup)
16+
Step 3 : Once found, add Slave as peer
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Step 4 : Register for send callback
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Step 5 : Start Transmitting data from Master to Slave
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Flow: Slave
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Step 1 : ESPNow Init on Slave
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Step 2 : Update the SSID of Slave with a prefix of `slave`
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Step 3 : Set Slave in AP mode
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Step 4 : Register for receive callback and wait for data
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Step 5 : Once data arrives, print it in the serial monitor
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Note: Master and Slave have been defined to easily understand the setup.
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Based on the ESPNOW API, there is no concept of Master and Slave.
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Any devices can act as master or salve.
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*/
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#include <esp_now.h>
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#include <WiFi.h>
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#define CHANNEL 1
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// Init ESP Now with fallback
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void InitESPNow() {
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if (esp_now_init() == ESP_OK) {
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Serial.println("ESPNow Init Success");
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}
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else {
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Serial.println("ESPNow Init Failed");
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// Retry InitESPNow, add a counte and then restart?
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// InitESPNow();
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// or Simply Restart
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ESP.restart();
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}
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}
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// config AP SSID
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void configDeviceAP() {
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char* SSID = "Slave_1";
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bool result = WiFi.softAP(SSID, "Slave_1_Password", CHANNEL, 0);
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if (!result) {
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Serial.println("AP Config failed.");
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} else {
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Serial.println("AP Config Success. Broadcasting with AP: " + String(SSID));
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}
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}
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void setup() {
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Serial.begin(115200);
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Serial.println("ESPNow/Basic/Slave Example");
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//Set device in AP mode to begin with
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WiFi.mode(WIFI_AP);
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// configure device AP mode
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configDeviceAP();
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// This is the mac address of the Slave in AP Mode
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Serial.print("AP MAC: "); Serial.println(WiFi.softAPmacAddress());
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// Init ESPNow with a fallback logic
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InitESPNow();
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// Once ESPNow is successfully Init, we will register for recv CB to
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// get recv packer info.
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esp_now_register_recv_cb(OnDataRecv);
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}
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// callback when data is recv from Master
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void OnDataRecv(const uint8_t *mac_addr, const uint8_t *data, int data_len) {
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char macStr[18];
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snprintf(macStr, sizeof(macStr), "%02x:%02x:%02x:%02x:%02x:%02x",
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mac_addr[0], mac_addr[1], mac_addr[2], mac_addr[3], mac_addr[4], mac_addr[5]);
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Serial.print("Last Packet Recv from: "); Serial.println(macStr);
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Serial.print("Last Packet Recv Data: "); Serial.println(*data);
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Serial.println("");
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}
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void loop() {
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// Chill
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}

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