Simple two-way communication in which the slave sends a reply when it receives a message.
EspnowTwoWaySlave.ino
// EspnowTwoWaySlave.ino
// a minimal program derived from
// https://github.com/HarringayMakerSpace/ESP-Now
// This is the program that receives the data and sends a reply. (The Slave)
//=============
#include <ESP8266WiFi.h>
extern "C" {
#include <espnow.h>
#include <user_interface.h>
}
// it seems that the mac address needs to be set before setup() is called
// and the inclusion of user_interface.h facilitates that
// presumably there is a hidden call to initVariant()
/* Set a private Mac Address
* http://serverfault.com/questions/40712/what-range-of-mac-addresses-can-i-safely-use-for-my-virtual-machines
* Note: the point of setting a specific MAC is so you can replace this Gateway ESP8266 device with a new one
* and the new gateway will still pick up the remote sensors which are still sending to the old MAC
*/
uint8_t mac[] = {0x36, 0x33, 0x33, 0x33, 0x33, 0x33};
//=============
void initVariant() {
WiFi.mode(WIFI_AP);
wifi_set_macaddr(SOFTAP_IF, &mac[0]);
}
//==============
#define WIFI_CHANNEL 4
// keep in sync with slave struct
struct __attribute__((packed)) DataStruct {
char text[32];
unsigned int time;
};
DataStruct receivedData;
DataStruct replyData;
//~ uint8_t incomingData[sizeof(receivedData)];
//============
void setup() {
Serial.begin(115200); Serial.println();
Serial.println("Starting EspnowTwoWaySlave.ino");
Serial.print("This node AP mac: "); Serial.println(WiFi.softAPmacAddress());
Serial.print("This node STA mac: "); Serial.println(WiFi.macAddress());
if (esp_now_init()!=0) {
Serial.println("*** ESP_Now init failed");
while(true) {};
}
// role set to COMBO so it can receive and send - not sure this is essential
esp_now_set_self_role(ESP_NOW_ROLE_COMBO);
esp_now_register_recv_cb(receiveCallBackFunction);
strcpy(replyData.text, "Goodnight John-Boy");
Serial.print("Message "); Serial.println(replyData.text);
Serial.println("End of setup - waiting for messages");
}
//============
void loop() {
}
//============
void receiveCallBackFunction(uint8_t *senderMac, uint8_t *incomingData, uint8_t len) {
memcpy(&receivedData, incomingData, sizeof(receivedData));
Serial.print("NewMsg ");
Serial.print("MacAddr ");
for (byte n = 0; n < 6; n++) {
Serial.print (senderMac[n], HEX);
}
Serial.print(" MsgLen ");
Serial.print(len);
Serial.print(" Name ");
Serial.print(receivedData.text);
Serial.print(" Time ");
Serial.print(receivedData.time);
Serial.println();
sendReply(senderMac);
}
//=============
void sendReply(uint8_t *macAddr) {
// create a peer with the received mac address
esp_now_add_peer(macAddr, ESP_NOW_ROLE_COMBO, WIFI_CHANNEL, NULL, 0);
replyData.time = millis();
uint8_t byteArray[sizeof(replyData)];
memcpy(byteArray, &replyData, sizeof(replyData));
esp_now_send(NULL, byteArray, sizeof(replyData)); // NULL means send to all peers
Serial.println("sendReply sent data");
// data sent so delete the peer
esp_now_del_peer(macAddr);
}
EspnowTwoWayController.ino
// EspnowTwoWayController.ino
// a minimal program derived from
// https://github.com/HarringayMakerSpace/ESP-Now
// This is the program that sends the data and receives the reply. (The Controller)
//=============
#include <ESP8266WiFi.h>
extern "C" {
#include <espnow.h>
}
// this is the MAC Address of the slave which receives these sensor readings
uint8_t remoteMac[] = {0x36, 0x33, 0x33, 0x33, 0x33, 0x33};
#define WIFI_CHANNEL 4
// must match slave struct
struct __attribute__((packed)) DataStruct {
char text[32];
unsigned long time;
};
DataStruct sendingData;
DataStruct receivedData;
// receivedData could use a completely different struct as long as it matches
// the reply that is sent by the slave
unsigned long lastSentMillis;
unsigned long sendIntervalMillis = 1000;
unsigned long sentMicros;
unsigned long ackMicros;
unsigned long replyMicros;
unsigned long lastBlinkMillis;
unsigned long fastBlinkMillis = 200;
unsigned long slowBlinkMillis = 700;
unsigned long blinkIntervalMillis = slowBlinkMillis;
byte ledPin = 14;
//==============
void setup() {
Serial.begin(115200); Serial.println();
Serial.println("Starting EspnowTwoWayController.ino");
WiFi.mode(WIFI_STA); // Station mode for esp-now controller
WiFi.disconnect();
Serial.printf("This mac: %s, ", WiFi.macAddress().c_str());
Serial.printf("target mac: %02x%02x%02x%02x%02x%02x", remoteMac[0], remoteMac[1], remoteMac[2], remoteMac[3], remoteMac[4], remoteMac[5]);
Serial.printf(", channel: %i\n", WIFI_CHANNEL);
if (esp_now_init() != 0) {
Serial.println("*** ESP_Now init failed");
while(true) {};
}
// role set to COMBO so it can send and receive - not sure this is essential
esp_now_set_self_role(ESP_NOW_ROLE_COMBO);
esp_now_add_peer(remoteMac, ESP_NOW_ROLE_COMBO, WIFI_CHANNEL, NULL, 0);
esp_now_register_send_cb(sendCallBackFunction);
esp_now_register_recv_cb(receiveCallBackFunction);
strcpy(sendingData.text, "Hello World");
Serial.print("Message "); Serial.println(sendingData.text);
pinMode(ledPin, OUTPUT);
digitalWrite(ledPin, HIGH);
delay(500);
digitalWrite(ledPin, LOW);
Serial.println("Setup finished");
}
//==============
void loop() {
sendData();
blinkLed();
}
//==============
void sendData() {
if (millis() - lastSentMillis >= sendIntervalMillis) {
lastSentMillis += sendIntervalMillis;
sendingData.time = millis();
uint8_t byteArray[sizeof(sendingData)];
memcpy(byteArray, &sendingData, sizeof(sendingData));
sentMicros = micros();
esp_now_send(NULL, byteArray, sizeof(sendingData)); // NULL means send to all peers
Serial.println("Loop sent data");
}
}
//==============
void sendCallBackFunction(uint8_t* mac, uint8_t sendStatus) {
ackMicros = micros();
Serial.print("Trip micros "); Serial.println(ackMicros - sentMicros);
Serial.printf("Send status = %i", sendStatus);
Serial.println();
if (sendStatus == 0) {
blinkIntervalMillis = fastBlinkMillis;
}
else {
blinkIntervalMillis = slowBlinkMillis;
}
}
//================
void receiveCallBackFunction(uint8_t *senderMac, uint8_t *incomingData, uint8_t len) {
replyMicros = micros();
Serial.print("Reply Trip micros "); Serial.println(replyMicros - sentMicros);
memcpy(&receivedData, incomingData, sizeof(receivedData));
Serial.print("NewReply ");
Serial.print("MacAddr ");
for (byte n = 0; n < 6; n++) {
Serial.print (senderMac[n], HEX);
}
Serial.print(" MsgLen ");
Serial.print(len);
Serial.print(" Text ");
Serial.print(receivedData.text);
Serial.print(" Time ");
Serial.print(receivedData.time);
Serial.println();
Serial.println();
}
//================
void blinkLed() {
if (millis() - lastBlinkMillis >= blinkIntervalMillis) {
lastBlinkMillis += blinkIntervalMillis;
digitalWrite(ledPin, ! digitalRead(ledPin));
}
}
Have fun ...
...R
