Restore esp32 MicroPython sources (main, benchmark_peers)

Adjust .gitignore to ignore esp32/* except *.py so firmware .bin stays untracked.

Made-with: Cursor

esp32/main.py

@@ -0,0 +1,63 @@
+# Serial-to-ESP-NOW bridge: receives from Pi on UART, forwards to ESP-NOW peers.
+# Wire format: first 6 bytes = destination MAC, rest = payload. Address is always 6 bytes.
+from machine import Pin, UART
+import espnow
+import network
+import time
+
+UART_BAUD = 912000
+BROADCAST = b"\xff\xff\xff\xff\xff\xff"
+MAX_PEERS = 20
+
+network.WLAN(network.STA_IF).active(True)
+esp = espnow.ESPNow()
+esp.active(True)
+esp.add_peer(BROADCAST)
+
+uart = UART(1, UART_BAUD, tx=Pin(21), rx=Pin(6))
+
+# Track last send time per peer for LRU eviction (remove oldest when at limit).
+last_used = {BROADCAST: time.ticks_ms()}
+
+
+# ESP_ERR_ESPNOW_EXIST: peer already registered (ignore when adding).
+ESP_ERR_ESPNOW_EXIST = -12395
+
+
+def ensure_peer(addr):
+    """Ensure addr is in the peer list. When at 20 peers, remove the oldest-used (LRU)."""
+    peers = esp.get_peers()
+    peer_macs = [p[0] for p in peers]
+    if addr in peer_macs:
+        return
+    if len(peer_macs) >= MAX_PEERS:
+        # Remove the peer we used least recently (oldest).
+        oldest_mac = None
+        oldest_ts = time.ticks_ms()
+        for mac in peer_macs:
+            if mac == BROADCAST:
+                continue
+            ts = last_used.get(mac, 0)
+            if ts <= oldest_ts:
+                oldest_ts = ts
+                oldest_mac = mac
+        if oldest_mac is not None:
+            esp.del_peer(oldest_mac)
+            last_used.pop(oldest_mac, None)
+    try:
+        esp.add_peer(addr)
+    except OSError as e:
+        if e.args[0] != ESP_ERR_ESPNOW_EXIST:
+            raise
+
+
+while True:
+    if uart.any():
+        data = uart.read()
+        if not data or len(data) < 6:
+            continue
+        addr = data[:6]
+        payload = data[6:]
+        ensure_peer(addr)
+        esp.send(addr, payload)
+        last_used[addr] = time.ticks_ms()