feat(espnow): ping request/response with jittered delay

Co-authored-by: Cursor <cursoragent@cursor.com>

src/espnow_transport.py

@@ -1,6 +1,7 @@
 """ESP-NOW receive loop and boot announce."""
 
 import asyncio
+import urandom
 
 import espnow
 import network
@@ -12,13 +13,21 @@ from espnow_wire import (
     MSG_CMD,
     MSG_GROUP_CMD,
     MSG_GROUPS,
+    MSG_PING_REQ,
     cmd_envelope,
     pack_announce,
+    pack_ping_rsp,
     parse_group_cmd,
     parse_groups,
+    parse_ping_req,
     wire_msg_type,
 )
+
 from controller_messages import process_data
+from settings import WIFI_CHANNEL_DEFAULT
+
+_PING_DELAY_MS_MIN = 50
+_PING_DELAY_MS_MAX = 500
 
 _esp = None
 _groups_received = False
@@ -26,14 +35,14 @@ _groups_received = False
 
 def init_espnow(settings):
     global _esp
-    ch = 6
     try:
-        ch = int(settings.get("wifi_channel", 1))
+        ch = int(settings.get("wifi_channel", WIFI_CHANNEL_DEFAULT))
     except (TypeError, ValueError):
-        pass
+        ch = WIFI_CHANNEL_DEFAULT
     ch = max(1, min(11, ch))
     sta = network.WLAN(network.STA_IF)
     sta.active(True)
+    sta.config(pm=network.WLAN.PM_NONE)
     sta.config(channel=ch)
     _esp = espnow.ESPNow()
     _esp.active(True)
@@ -44,6 +53,42 @@ def init_espnow(settings):
     return _esp
 
 
+def _send_ping_rsp(host, settings, ping_id, delay_ms):
+    import utime
+
+    utime.sleep_ms(delay_ms)
+    if _esp is None or not host or len(host) != 6:
+        return
+    pkt = pack_ping_rsp(ping_id, settings.get("name", "led"))
+    try:
+        try:
+            _esp.add_peer(host)
+        except Exception:
+            pass
+        _esp.send(host, pkt)
+        print("espnow ping rsp", ping_id, delay_ms, "ms")
+    except Exception as e:
+        print("espnow ping rsp failed:", e)
+
+
+async def _send_ping_rsp_delayed(host, settings, ping_id):
+    span = _PING_DELAY_MS_MAX - _PING_DELAY_MS_MIN
+    delay_ms = _PING_DELAY_MS_MIN + (urandom.getrandbits(10) % (span + 1))
+    await asyncio.sleep(delay_ms / 1000)
+    _send_ping_rsp(host, settings, ping_id, delay_ms)
+
+
+def _schedule_ping_rsp(host, settings, ping_id):
+    span = _PING_DELAY_MS_MAX - _PING_DELAY_MS_MIN
+    delay_ms = _PING_DELAY_MS_MIN + (urandom.getrandbits(10) % (span + 1))
+    try:
+        import _thread
+
+        _thread.start_new_thread(_send_ping_rsp, (host, settings, ping_id, delay_ms))
+    except ImportError:
+        asyncio.create_task(_send_ping_rsp_delayed(host, settings, ping_id))
+
+
 def send_boot_announce(settings):
     if _esp is None:
         return
@@ -61,7 +106,7 @@ def send_boot_announce(settings):
         print("espnow announce failed:", e)
 
 
-def _handle_packet(pkt, settings, presets):
+def _handle_packet(host, pkt, settings, presets):
     global _groups_received
     mt = wire_msg_type(pkt)
     if mt == MSG_GROUPS:
@@ -91,6 +136,11 @@ def _handle_packet(pkt, settings, presets):
         if env:
             process_data(env, settings, presets, save=save)
         return
+    if mt == MSG_PING_REQ:
+        ping_id = parse_ping_req(pkt)
+        if ping_id is not None and host and len(host) == 6:
+            _schedule_ping_rsp(host, settings, ping_id)
+        return
     if mt == MSG_ANNOUNCE:
         return
 
@@ -112,7 +162,7 @@ async def espnow_receive_loop(settings, presets, wdt=None):
                 wdt.feed()
             continue
         try:
-            _handle_packet(msg, settings, presets)
+            _handle_packet(host, msg, settings, presets)
         except Exception as e:
             print("espnow rx error:", e)
         if wdt:

src/espnow_wire.py

@@ -9,6 +9,8 @@ MSG_ANNOUNCE = 0x01
 MSG_GROUPS = 0x02
 MSG_CMD = 0x03
 MSG_GROUP_CMD = 0x04
+MSG_PING_REQ = 0x05
+MSG_PING_RSP = 0x06
 
 BROADCAST_MAC = b"\xff\xff\xff\xff\xff\xff"
 
@@ -104,6 +106,29 @@ def cmd_envelope(payload):
     return env[:need], save
 
 
+def pack_ping_req(ping_id):
+    body = struct.pack("<I", int(ping_id) & 0xFFFFFFFF)
+    return _pack_header(MSG_PING_REQ, body)
+
+
+def parse_ping_req(payload):
+    if len(payload) >= 2 and payload[0] == WIRE_MAGIC:
+        if payload[1] != MSG_PING_REQ:
+            return None
+        body = payload[2:]
+    else:
+        body = payload
+    if len(body) < 4:
+        return None
+    return struct.unpack("<I", body[:4])[0]
+
+
+def pack_ping_rsp(ping_id, name):
+    name_b = name.encode("utf-8")
+    body = struct.pack("<I", int(ping_id) & 0xFFFFFFFF) + bytes([len(name_b)]) + name_b
+    return _pack_header(MSG_PING_RSP, body)
+
+
 def wire_msg_type(payload):
     if len(payload) >= 2 and payload[0] == WIRE_MAGIC:
         return payload[1]