diff --git a/README.md b/README.md
index b4f5654..a64ffde 100644
--- a/README.md
+++ b/README.md
@@ -78,6 +78,13 @@ USB连接Air780e，选择 `Luatools/resource/618_lua_lod/版本号` 目录下的
 
 目前固件包含`gpio`、`uart`、`pwm`、`wdt`、`crypto`、`rtc`、`network`、`sntp`、`tls`、`wlan`、`pm`、`cjson`、`ntp`、`shell`、`dbg`。
 
+# 保活 API 说明
+
+API 提供 GET 和 POST 请求支持。
+
+- GET 请求返回 POST 请求存储的时间戳
+- POST 请求接收 `{ "expiry": "1732622763" }`，并存储
+
 # 致谢
 
 本项目参考[低成本短信转发器](https://github.com/chenxuuu/sms_forwarding)而来，尤其是PDU相关代码，没有`chenxuuu`的这份项目和[50元内自制短信转发器（Air780E+ESP32C3）](https://www.chenxublog.com/2022/10/28/19-9-sms-forwarding-air780e-esp32c3.html)这篇文章，我不会这么快就完成开发。
diff --git a/air780_helper.lua b/air780_helper.lua
index 671e692..bedd415 100644
--- a/air780_helper.lua
+++ b/air780_helper.lua
@@ -38,6 +38,10 @@ end)
 -- 发送AT指令
 function air780_helper.send_at_command(command)
     uart.write(uart_id, command)
+    -- 如果是PDU模式下的短信内容，直接返回
+    if command:sub(1, 6) == "001110" then
+        return
+    end
     uart.write(uart_id, "\r\n")
     log.debug("air780_helper", "发送AT指令\""..command.."\"")
 end
@@ -80,6 +84,20 @@ sys.subscribe(constants.uart_ready_message, function()
             return
         end
 
+        -- 响应发送短信指令
+        if current_line:find(">", 1, true) then
+            -- log.debug("air780_helper", "捕获到短信发送提示符")
+            sys.publish(constants.air780_helper_sms_send_ready)
+            return
+        end
+
+        -- 响应发送短信成功
+        if current_line:find("+CMGS:", 1, true) then
+            -- log.debug("air780_helper", "捕获到短信发送成功")
+            sys.publish(constants.air780_send_sms_success)
+            return
+        end
+
         local urc = current_line:match("^%+(%w+)")
 
         if urc then -- URC上报
@@ -129,7 +147,7 @@ sys.subscribe(constants.uart_ready_message, function()
                         end
                     until #data == 0
                 end
-             end
+            end
         end
     end
 end)
@@ -145,4 +163,36 @@ function air780_helper.send_at_command_and_wait(command, topic_listen_to, timeou
     end
 end
 
+function air780_helper.topic_wait(topic, timeout)
+    local is_successful, r1, r2, r3 = sys.waitUntil(topic, timeout or 1000)
+    return is_successful
+end
+
+function air780_helper.sent_sms(to, text)
+    local logging_tag = "air780_helper.sent_sms"
+    local data, len = pdu_helper.encode_pdu(to, text)
+    if not data or not len then
+        log.error(logging_tag, "短信编码失败")
+        return false
+    end
+    air780_helper.send_at_command("AT+CMGS=" .. len)
+    
+    -- 增加调试信息
+    log.debug(logging_tag, "等待短信发送提示符")
+    local result = air780_helper.topic_wait(constants.air780_helper_sms_send_ready, 3000)
+    if not result then
+        log.error(logging_tag, "短信发送失败，AT+CMGS=" .. len .. " 超时")
+        return false
+    end
+
+    air780_helper.send_at_command(data .. "\x1A")
+    local result = air780_helper.topic_wait(constants.air780_send_sms_success, 5000)
+    if result then
+        log.info(logging_tag, "短信发送成功")
+        return true
+    else
+        log.error(logging_tag, "短信发送失败")
+        return false
+    end
+end
 return air780_helper
diff --git a/config.lua b/config.lua
index d88c479..9571982 100644
--- a/config.lua
+++ b/config.lua
@@ -18,15 +18,22 @@ config.disable_rndis = true
 -- 而1156版本AT固件第一次检测有概率检测不到SIM卡，需要重试
 config.retry_sim_detection = true
 
+-- 续期 API
+config.renew_api = "https://api.example.com/sim/expiry"
+-- 续期间隔
+config.renew_day = 180
+-- 续期检查间隔，单位小时。为 0 时禁用
+config.renew_check_interval = 0
+-- 续期接收号码
+config.renew_number = "+8613881388138"
+-- 续期短信内容
+config.renew_content = "注意余额"
+
 config.wifi = {
     {
         ssid = "Wi-Fi名",
         password = "Wi-Fi密码",
     },
-    -- {
-    --     ssid = "",
-    --     password = "",
-    -- }
 }
 
 -- 手动配置DNS服务器
@@ -73,7 +80,7 @@ config.notification_channel = {
     -- telegram 机器人
     telegram = {
         enabled = false,
-        -- Webhook地址
+        -- Webhook地址， https://api.telegram.org/bot<token>/sendMessage
         webhook_url = "",
         -- chat_id, 通过 https://api.telegram.org/bot<token>/getUpdates 获取
         chat_id = ""
diff --git a/constants.lua b/constants.lua
index 2d778fd..6869e45 100644
--- a/constants.lua
+++ b/constants.lua
@@ -32,5 +32,7 @@ constants.air780_message_topic_new_message_notification_configured = "NEW_MESSAG
 constants.air780_message_topic_network_connected = "NETWORK_CONNECTED"
 constants.air780_message_topic_new_sms_received = "NEW_SMS_RECEIVED"
 constants.air780_message_topic_new_notification_request = "NEW_NOTIFICATION_REQUEST"
+constants.air780_helper_sms_send_ready = "SMS_SEND_READY"
+constants.air780_send_sms_success = "SMS_SENT_SUCCESSFULLY"
 
 return constants
diff --git a/main.lua b/main.lua
index d4df959..9480c8d 100644
--- a/main.lua
+++ b/main.lua
@@ -110,7 +110,7 @@ sys.taskInit(function ()
             log.info(logging_tag, "GPRS已附着")
             break
         else
-            log.info(logging_tag, "GPRS未附着，将在5秒后重新检查")
+            log.info(logging_tag, "GPRS未附着, 将在5秒后重新检查")
             sys.wait(5000)
         end
     end
@@ -131,6 +131,16 @@ sys.taskInit(function ()
     led_helper.light_status_led()
 end)
 
+sys.taskInit(function()
+    renew = require("renew")
+    sys.waitUntil(constants.air780_message_topic_new_message_notification_configured)
+    sys.waitUntil("NTP_UPDATE")
+    if config.renew_check_interval > 0 then
+        log.info("renew", "自动续期启动")
+        renew.renew()
+    end
+end)
+
 --[[
 long_sms_buffer = {
     [phone_number] = {
diff --git a/pdu_helper.lua b/pdu_helper.lua
index fac935d..3248a36 100644
--- a/pdu_helper.lua
+++ b/pdu_helper.lua
@@ -363,4 +363,18 @@ function pdu_helper.decode_pdu(pdu, len)
     return sender_number, sms_content_in_utf8, sms_receive_time, long_sms, total_message_count, current_idx, sms_id
 end
 
+-- 生成PDU短信编码
+-- 仅支持单条短信，传入数据为utf8编码
+-- 返回值为pdu编码与长度
+function pdu_helper.encode_pdu(num,data)
+    data = utf8_to_ucs2(data):toHex()
+    local numlen, datalen, pducnt, pdu, pdulen, udhi = string.format("%02X", #num), #data / 2, 1, "", "", ""
+    if datalen > 140 then--短信内容太长啦
+        data = data:sub(1, 140 * 2)
+    end
+    datalen = string.format("%02X", datalen)
+    pdu = "001110" .. numlen .. number_to_bcd_number(num) .. "000800" .. datalen .. data
+    return pdu, #pdu // 2 - 1
+end
+
 return pdu_helper
diff --git a/renew.lua b/renew.lua
new file mode 100644
index 0000000..ee386b8
--- /dev/null
+++ b/renew.lua
@@ -0,0 +1,88 @@
+local renew = {}
+
+local sys = require("sys")
+local sysplus = require("sysplus")
+local air780 = require("air780_helper")
+local config = require("config")
+
+-- 获取到期时间
+-- GET https://api.example.com/sim/expiry 1732622763
+function renew.get_expire_date()
+    local code, headers, body = http.request("GET", config.renew_api, {["User-Agent"] = "LuatOS/1.0.0 (Lua; ESP32; Air780)"}, nil, {ipv6=true}).wait()
+
+    -- 如果 code 为负数，说明请求失败
+    if code < 0 or code ~= 200 then
+        log.error("renew", "获取到期时间", "code=" .. code)
+        return nil
+    end
+    
+    -- 尝试将 body 转换为数字
+    local date = tonumber(body)
+    if not date then
+        log.error("renew", "获取到期时间", "未知时间格式：" .. tostring(body))
+        return nil
+    end
+
+    return date
+end
+
+-- 更新到期时间
+-- POST https://api.example.com/sim/expiry { "expiry": "1732622763" }
+function renew.update_expire_date(date)
+    local body = { expiry = date }
+    local code, headers, body = http.request("POST", config.renew_api, {["Content-Type"] = "application/json", ["User-Agent"] = "LuatOS/1.0.0 (Lua; ESP32; Air780)"}, json.encode(body), {ipv6=true}).wait()
+    if code ~= 200 then
+        log.error("renew", "更新到期时间", "code=" .. code)
+        return false
+    end
+    return true
+end
+
+-- 发送短信
+-- 发送短信后，更新到期时间，到期时间为当前时间戳 + config.renew_day
+function renew.send_sms()
+    if air780.sent_sms(config.renew_number, config.renew_content) then
+        log.debug("renew", "sent_sms success")
+        if renew.update_expire_date(os.time() + config.renew_day * 24 * 60 * 60) then
+            log.debug("renew", "更新到期时间成功")
+            return true
+        else
+            log.error("renew", "更新到期时间失败")
+            return false
+        end
+    else
+        log.error("renew", "发送短信失败")
+        return false
+    end
+    return true
+end
+
+-- 保活
+-- 如果 date 为空，则发送短信
+-- 如果当前时间戳大于等于 date，则发送短信
+-- 检查间隔为 config.renew_check_interval 单位小时
+function renew.renew()
+    while true do
+        local date = renew.get_expire_date()
+        if date == nil then
+            log.error("renew", "get_expire_date", "get_expire_date failed")
+            goto continue
+        end
+        if date == "" or os.time() >= date then
+            log.debug("renew", "已到期，开始保活")
+            if renew.send_sms() then
+                log.debug("renew", "保活成功")
+            else
+                log.error("renew", "保活失败")
+            end
+
+            goto continue
+        end
+        log.debug("renew", "时间未到，无需保活")
+
+        ::continue::
+        sys.wait(config.renew_check_interval * 60 * 60 * 1000)
+    end
+end
+
+return renew