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ESPNOW Multipeer #435

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0ae2aac
ESPNOW Multipeer
jlpoltrack Mar 29, 2026
edec745
No Target
jlpoltrack Mar 29, 2026
cc4b439
Add Power Define
jlpoltrack Mar 30, 2026
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78 changes: 41 additions & 37 deletions esp/mlrs-espnow-gcs/mlrs-espnow-gcs.ino
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@
// For use with ESP8266, ESP32, ESP32C3 and ESP32S3 modules.
// To use USB on ESP32C3 and ESP32S3, 'USB CDC On Boot' must be enabled in Tools.
//********************************************************
// 2. Mar. 2026
// 29. Mar. 2026
//********************************************************

#ifdef ESP8266
Expand All @@ -23,16 +23,20 @@

#define BAUD_RATE 115200 // baudrate for serial connection to GCS

// wifi channel — must match WIFI_CHANNEL on the bridge
// required for MSP systems, e.g. INAV
// MSP uses send/request, so the bridge won't transmit until polled
// for MAVLink systems this can be left commented out; scanning will find the bridge
//#define WIFI_CHANNEL 13
#define BIND_PHRASE "mlrs.0" // must match the mLRS bind phrase

//#define LISTEN_ONLY // uncomment to receive only; no serial data sent to bridge, only beacons

//#define USE_SERIAL1 // uncomment to use Serial1 instead of USB Serial for ESP32C3 and ESP32S3
//#define TX_PIN 43 // Serial1 TX pin
//#define RX_PIN 44 // Serial1 RX pin

// WiFi transmit power
// Uncomment one of the three power levels:
//#define WIFI_POWER_LOW // lowest power: -1 dBm (ESP32) / 0 dBm (ESP8266)
#define WIFI_POWER_MED // medium power: 5 dBm
//#define WIFI_POWER_MAX // maximum power: 19.5 dBm (ESP32) / 20.5 dBm (ESP8266)

//#define DEVICE_HAS_SINGLE_LED // uncomment for single on/off LED
//#define DEVICE_HAS_SINGLE_LED_RGB // uncomment for single RGB (NeoPixel/WS2812) LED
//#define LED_IO 8 // LED pin (comment out to disable)
Expand Down Expand Up @@ -82,6 +86,11 @@ int espnow_rxbuf_pop(uint8_t* buf, int maxlen)
return cnt;
}

// beacon: sent periodically so the bridge discovers us even when GCS app is idle
// includes bind phrase so only matching systems pair
#define ESPNOW_BEACON_LEN 11
const uint8_t espnow_beacon[ESPNOW_BEACON_LEN] = { 'm','L','R','S','-', BIND_PHRASE[0],BIND_PHRASE[1],BIND_PHRASE[2],BIND_PHRASE[3],BIND_PHRASE[4],BIND_PHRASE[5] };

// mac latch: once a bridge sends us data, we lock to its MAC and register it as a peer
volatile bool espnow_latched_mac_available;
uint8_t espnow_latched_mac[6];
Expand All @@ -102,13 +111,15 @@ void espnow_recv_cb(const esp_now_recv_info_t* info, const uint8_t* data, int le
#else
const uint8_t* sender_mac = mac;
#endif
bool is_beacon = (len == ESPNOW_BEACON_LEN && memcmp(data, "mLRS-", 5) == 0);
if (is_beacon && memcmp(data, espnow_beacon, ESPNOW_BEACON_LEN) != 0) return; // wrong bind phrase
if (!espnow_latched_mac_available) {
memcpy(espnow_latched_mac, sender_mac, 6);
espnow_latched_mac_available = true;
} else if (memcmp(sender_mac, espnow_latched_mac, 6) != 0) {
return; // ignore other senders
}
espnow_rxbuf_push(data, len);
if (!is_beacon) espnow_rxbuf_push(data, len);
}

uint8_t broadcast_mac[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
Expand All @@ -118,7 +129,6 @@ const uint8_t scan_channels[] = { 1, 6, 11, 13 };


bool is_connected;
unsigned long is_connected_tlast_ms;
bool wifi_initialized;
uint8_t buf[250];

Expand All @@ -130,26 +140,23 @@ uint8_t buf[250];
// scan channels until we hear from the bridge
void scan_for_bridge(void)
{
if (espnow_latched_mac_available) {
esp_now_del_peer(espnow_latched_mac);
espnow_latched_mac_available = false;
latched_peer_added = false;
}
while (true) {
for (int i = 0; i < (int)sizeof(scan_channels); i++) {
#ifdef ESP8266
wifi_set_channel(scan_channels[i]);
#else
esp_wifi_set_channel(scan_channels[i], WIFI_SECOND_CHAN_NONE);
#endif
// beacon on this channel so the bridge discovers us
esp_now_send(broadcast_mac, (uint8_t*)espnow_beacon, ESPNOW_BEACON_LEN);

unsigned long t = millis();
while (millis() - t < 500) {
led_tick_scanning();

while (SERIAL_PORT.available()) SERIAL_PORT.read(); // dump data while disconnected

if (espnow_rxbuf_head != espnow_rxbuf_tail) {
if (espnow_latched_mac_available) {
return;
}
delay(1);
Expand All @@ -172,12 +179,28 @@ void setup_wifi(void)
#ifdef ESP8266
// force 11b only for best reliability
wifi_set_phy_mode(PHY_MODE_11B);
// set transmit power
#if defined(WIFI_POWER_MAX)
WiFi.setOutputPower(20.5);
#elif defined(WIFI_POWER_MED)
WiFi.setOutputPower(5);
#else
WiFi.setOutputPower(0);
#endif
#else
// set country to EU to enable channels 1-13 (default may restrict to 1-11)
wifi_country_t country = { .cc = "EU", .schan = 1, .nchan = 13, .policy = WIFI_COUNTRY_POLICY_MANUAL };
esp_wifi_set_country(&country);
// force 11b only for best reliability
esp_wifi_set_protocol(WIFI_IF_STA, WIFI_PROTOCOL_11B);
// set transmit power
#if defined(WIFI_POWER_MAX)
WiFi.setTxPower(WIFI_POWER_19_5dBm);
#elif defined(WIFI_POWER_MED)
WiFi.setTxPower(WIFI_POWER_5dBm);
#else
WiFi.setTxPower(WIFI_POWER_MINUS_1dBm);
#endif
#endif

esp_now_init();
Expand All @@ -194,16 +217,7 @@ void setup_wifi(void)
esp_now_add_peer(&peer);
#endif

#ifdef WIFI_CHANNEL
// fixed channel — skip scanning, required for MSP (send/request) systems
#ifdef ESP8266
wifi_set_channel(WIFI_CHANNEL);
#else
esp_wifi_set_channel(WIFI_CHANNEL, WIFI_SECOND_CHAN_NONE);
#endif
#else
scan_for_bridge();
#endif
}


Expand All @@ -227,7 +241,6 @@ void setup()
latched_peer_added = false;

is_connected = false;
is_connected_tlast_ms = 0;
wifi_initialized = false;
}

Expand All @@ -241,16 +254,6 @@ void loop()
return;
}

unsigned long tnow_ms = millis();

// connection timeout
if (is_connected && (tnow_ms - is_connected_tlast_ms > 2000)) {
is_connected = false;
#ifndef WIFI_CHANNEL
scan_for_bridge();
#endif
}

// LED: blink pattern based on connection state
if (is_connected) {
led_tick_connected();
Expand All @@ -262,12 +265,11 @@ void loop()
int len = espnow_rxbuf_pop(buf, sizeof(buf));
if (len > 0) {
SERIAL_PORT.write(buf, len);
is_connected = true;
is_connected_tlast_ms = tnow_ms;
}

// register latched peer for unicast TX
// register latched peer for unicast TX and mark connected
if (espnow_latched_mac_available && !latched_peer_added) {
is_connected = true;
#ifdef ESP8266
esp_now_add_peer(espnow_latched_mac, ESP_NOW_ROLE_COMBO, 0, NULL, 0);
#else
Expand All @@ -283,10 +285,12 @@ void loop()
while (SERIAL_PORT.available() && rlen < (int)sizeof(buf)) {
buf[rlen++] = SERIAL_PORT.read();
}
#ifndef LISTEN_ONLY
if (rlen > 0) {
uint8_t* dest = espnow_latched_mac_available ? espnow_latched_mac : broadcast_mac;
esp_now_send(dest, buf, rlen);
}
#endif

delay(2);
}
94 changes: 74 additions & 20 deletions esp/mlrs-wireless-bridge/mlrs-wireless-bridge.ino
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@
// Basic but effective & reliable transparent WiFi or Bluetooth <-> serial bridge.
// Minimizes wireless traffic while respecting latency by better packeting algorithm.
//*******************************************************
// 21. Mar. 2026
// 29. Mar. 2026
//*********************************************************/
// inspired by examples from Arduino
// NOTES:
Expand Down Expand Up @@ -368,9 +368,23 @@ void ble_setup(String device_name) {
uint8_t espnow_rxbuf[ESPNOW_RXBUF_SIZE];
volatile uint16_t espnow_rxbuf_head;
volatile uint16_t espnow_rxbuf_tail;
volatile bool espnow_gcs_mac_available; // once a GCS sends us data, we lock to its MAC
uint8_t espnow_gcs_mac[6];
bool espnow_gcs_peer_added;

// beacon: includes bind phrase so only matching systems pair
#define ESPNOW_BEACON_LEN 11
uint8_t espnow_beacon[ESPNOW_BEACON_LEN] = { 'm','L','R','S','-', 0,0,0,0,0,0 };

// multi-peer: track up to 4 GCS peers
#define ESPNOW_MAX_PEERS 4

struct espnow_peer_t {
uint8_t mac[6];
bool registered; // esp_now_add_peer() done (main loop only)
volatile bool active; // slot occupied (set by callback, read by main loop)
volatile bool confirm_needed; // set by callback, cleared by main loop after sending confirm beacon
};

volatile espnow_peer_t espnow_peers[ESPNOW_MAX_PEERS];

uint8_t espnow_broadcast_mac[6] = { 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF };

void espnow_rxbuf_push(const uint8_t* data, int len) {
Expand All @@ -392,13 +406,30 @@ int espnow_rxbuf_pop(uint8_t* buf, int maxlen) {
}

void espnow_recv_callback(const uint8_t* sender_mac, const uint8_t* data, int len) {
if (!espnow_gcs_mac_available) { // accept only from the first sender we hear from
memcpy(espnow_gcs_mac, sender_mac, 6);
espnow_gcs_mac_available = true;
} else {
if (memcmp(sender_mac, espnow_gcs_mac, 6) != 0) return; // ignore other senders
bool is_beacon = (len == ESPNOW_BEACON_LEN && memcmp(data, "mLRS-", 5) == 0);
if (is_beacon && memcmp(data, espnow_beacon, ESPNOW_BEACON_LEN) != 0) return; // wrong bind phrase
// known peer
for (int i = 0; i < ESPNOW_MAX_PEERS; i++) {
if (espnow_peers[i].active && memcmp((void*)espnow_peers[i].mac, sender_mac, 6) == 0) {
if (is_beacon) {
espnow_peers[i].confirm_needed = true;
} else {
espnow_rxbuf_push(data, len);
}
return;
}
}
// unknown — claim first free slot
for (int i = 0; i < ESPNOW_MAX_PEERS; i++) {
if (!espnow_peers[i].active) {
memcpy((void*)espnow_peers[i].mac, sender_mac, 6);
espnow_peers[i].registered = false;
espnow_peers[i].confirm_needed = true;
espnow_peers[i].active = true; // publish last — main loop reads this
if (!is_beacon) espnow_rxbuf_push(data, len);
return;
}
}
espnow_rxbuf_push(data, len);
}

#ifdef ESP8266
Expand All @@ -419,10 +450,27 @@ void espnow_add_peer_mac(uint8_t* mac, int wifi_channel) {
#endif
}

void espnow_register_peers(int wifi_channel) {
for (int i = 0; i < ESPNOW_MAX_PEERS; i++) {
if (!espnow_peers[i].active) continue;
if (!espnow_peers[i].registered) {
espnow_add_peer_mac((uint8_t*)espnow_peers[i].mac, wifi_channel);
espnow_peers[i].registered = true;
}
if (espnow_peers[i].confirm_needed) {
espnow_peers[i].confirm_needed = false;
esp_now_send((uint8_t*)espnow_peers[i].mac, (uint8_t*)espnow_beacon, ESPNOW_BEACON_LEN);
}
}
}

void espnow_setup(int wifi_channel) {
espnow_rxbuf_head = espnow_rxbuf_tail = 0;
espnow_gcs_mac_available = false;
espnow_gcs_peer_added = false;
for (int i = 0; i < ESPNOW_MAX_PEERS; i++) {
espnow_peers[i].active = false;
espnow_peers[i].registered = false;
espnow_peers[i].confirm_needed = false;
}
WiFi.mode(WIFI_STA);
WiFi.disconnect();
#ifdef ESP8266
Expand All @@ -448,14 +496,15 @@ void espnow_setup(int wifi_channel) {
DBG_PRINTLN("ESP-NOW started");
}

void espnow_send(int wifi_channel, uint8_t* buf, int len) {
if (espnow_gcs_mac_available) { // if gcs seen, send unicast; otherwise broadcast
if (!espnow_gcs_peer_added) { // ensure latched peer is registered
espnow_add_peer_mac(espnow_gcs_mac, wifi_channel);
espnow_gcs_peer_added = true;
void espnow_send(uint8_t* buf, int len) {
bool any = false;
for (int i = 0; i < ESPNOW_MAX_PEERS; i++) {
if (espnow_peers[i].active && espnow_peers[i].registered) {
esp_now_send((uint8_t*)espnow_peers[i].mac, buf, len);
any = true;
}
esp_now_send(espnow_gcs_mac, buf, len);
} else {
}
if (!any) {
esp_now_send(espnow_broadcast_mac, buf, len);
}
}
Expand Down Expand Up @@ -1059,6 +1108,10 @@ class tESPNOWHandler : public tWifiHandler {
void Init() {
tWifiHandler::Init();
device_name = device_name + " ESPNOW";
// populate beacon with bind phrase
for (int i = 0; i < 6 && i < (int)g_bindphrase.length(); i++) {
espnow_beacon[5 + i] = g_bindphrase[i];
}
}

void wifi_setup() override {
Expand All @@ -1068,6 +1121,7 @@ class tESPNOWHandler : public tWifiHandler {

void Loop(uint8_t* buf, int sizeofbuf) override {
if (sizeofbuf > 250) sizeofbuf = 250; // cap at 250 bytes (esp-now max payload)
espnow_register_peers(g_wifichannel);
int len = espnow_rxbuf_pop(buf, sizeofbuf);
if (len > 0) {
SERIAL.write(buf, len);
Expand All @@ -1077,7 +1131,7 @@ class tESPNOWHandler : public tWifiHandler {
}

void wifi_write(uint8_t* buf, int len) override {
espnow_send(g_wifichannel, buf, len);
espnow_send(buf, len);
}
};
tESPNOWHandler espnow_handler;
Expand Down