diff --git a/lsn50-v2-xkc-y25-v-drainage/config/codec-production.js b/lsn50-v2-xkc-y25-v-drainage/config/codec-production.js
new file mode 100644
index 0000000..398471e
--- /dev/null
+++ b/lsn50-v2-xkc-y25-v-drainage/config/codec-production.js
@@ -0,0 +1,106 @@
+// ChirpStack v4+ Codec (JavaScript)
+// LSN50 v2.x - Production codec for PA12 + Downlink control (TDC + 5VT)
+//
+// Verified mapping (uplink): PA12 = bytes[6] bit1 (0x02) on FPort 2 (MOD=1, 11 bytes)
+// Downlink commands (Dragino common):
+// - Set TDC (seconds): 0x01 + 3 bytes (big-endian)
+// - Set 5VT (ms): 0x07 + 2 bytes (big-endian)
+
+const CFG = {
+  INVERT_LOGIC: false,
+  EXPECTED_UP_FPORT: 2,
+  EXPECTED_UP_LEN: 11,
+  CMD_FPORT: 2,
+  LIMITS: {
+    TDC_SEC_MIN: 5,
+    TDC_SEC_MAX: 86400,
+    VT_MS_MIN: 0,
+    VT_MS_MAX: 60000
+  }
+};
+
+function decodeUplink(input) {
+  const b = input.bytes || [];
+  const fPort = input.fPort;
+  const rawHex = b.map(x => x.toString(16).padStart(2, "0")).join("");
+
+  const byte6 = (b.length > 6) ? b[6] : 0x00;
+  const pa12 = (byte6 & 0x02) ? 1 : 0;
+  const drenaje = CFG.INVERT_LOGIC ? (pa12 ? 0 : 1) : pa12;
+
+  const warnings = [];
+  if (fPort !== CFG.EXPECTED_UP_FPORT) warnings.push(`Unexpected fPort=${fPort}, expected ${CFG.EXPECTED_UP_FPORT}`);
+  if (b.length !== CFG.EXPECTED_UP_LEN) warnings.push(`Unexpected payload length=${b.length}, expected ${CFG.EXPECTED_UP_LEN}`);
+
+  return {
+    data: {
+      drenaje,
+      pa12,
+      byte6,
+      payload_len: b.length,
+      payload_hex: rawHex,
+      warnings: warnings.length ? warnings : undefined
+    }
+  };
+}
+
+function u16be(n) {
+  return [(n >> 8) & 0xff, n & 0xff];
+}
+
+function u24be(n) {
+  return [(n >> 16) & 0xff, (n >> 8) & 0xff, n & 0xff];
+}
+
+function assertInt(name, v) {
+  if (typeof v !== "number" || !isFinite(v) || Math.floor(v) !== v) {
+    throw new Error(`${name} must be an integer`);
+  }
+}
+
+function clampInt(name, v, min, max) {
+  assertInt(name, v);
+  if (v < min || v > max) throw new Error(`${name} out of range [${min}, ${max}]: ${v}`);
+  return v;
+}
+
+function encodeDownlink(input) {
+  const data = (input && input.data) ? input.data : {};
+  const cmd = data.cmd;
+
+  if (!cmd) {
+    return { bytes: [] };
+  }
+
+  if (cmd === "set_tdc") {
+    const tdc = clampInt("tdc_sec", data.tdc_sec, CFG.LIMITS.TDC_SEC_MIN, CFG.LIMITS.TDC_SEC_MAX);
+    const bytes = [0x01].concat(u24be(tdc));
+    return {
+      fPort: CFG.CMD_FPORT,
+      bytes
+    };
+  }
+
+  if (cmd === "set_5vt") {
+    const vt = clampInt("vt_ms", data.vt_ms, CFG.LIMITS.VT_MS_MIN, CFG.LIMITS.VT_MS_MAX);
+    const bytes = [0x07].concat(u16be(vt));
+    return {
+      fPort: CFG.CMD_FPORT,
+      bytes
+    };
+  }
+
+  if (cmd === "profile_active") {
+    const vt = clampInt("vt_ms", (data.vt_ms ?? 2000), CFG.LIMITS.VT_MS_MIN, CFG.LIMITS.VT_MS_MAX);
+    const bytes = [0x07].concat(u16be(vt));
+    return { fPort: CFG.CMD_FPORT, bytes };
+  }
+
+  if (cmd === "profile_sleep") {
+    const vt = clampInt("vt_ms", (data.vt_ms ?? 0), CFG.LIMITS.VT_MS_MIN, CFG.LIMITS.VT_MS_MAX);
+    const bytes = [0x07].concat(u16be(vt));
+    return { fPort: CFG.CMD_FPORT, bytes };
+  }
+
+  throw new Error(`Unknown cmd: ${cmd}`);
+}
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