mobile_comm/luatos/air780epm/module/Air780EPM/demo/vd960Air/uart_app.lua

--[[
@module  uart_app
@summary vd960Air 串口应用功能模块: UART1 <-> vd960DBN 帧协议对接
@version 0.1
@date    2026.08.31
@usage
核心职责:
1、打开 UART1(对接 vd960DBN CH32V208 串口1 PB6/PB7);
2、上行: 接收 vd960DBN 的 JSON 帧(复用《DLD960_IoT_MQTT协议》命令面),
   校验后发布 SEND_DATA_REQ 消息 → mqtt_sender publish 到 dld960/{sn}/dev;
3、下行: 订阅 RECV_DATA_FROM_SERVER 消息,将 MQTT 下行 JSON 组帧后经 UART1 下发 vd960DBN。

UART 链路帧格式(设计稿 v0.1,待与 vd960DBN 侧联调确认):
┌──────┬───────┬───────┬────────────────────┬──────┐
│ HEAD │ LEN_H │ LEN_L │      PAYLOAD       │ SUM  │
│ 0x7D │ 1B    │ 1B    │  JSON(≤2048B)      │ 1B   │
└──────┴───────┴───────┴────────────────────┴──────┘
- HEAD: 0x7D(与 DBN↔Loop 的 0x7F 帧区分,4G 链路独立魔数)
- LEN:  uint16 大端,PAYLOAD 字节数
- SUM:  uint8 累加和,覆盖 HEAD+LEN_H+LEN_L+PAYLOAD 全部字节取低 8 位
- 方向: 双向对称(vd960DBN 发同样帧格式)

状态机: IDLE → HEAD → LEN_H → LEN_L → DATA → SUM → COMPLETE
注意: 状态机按 LEN 精确吃字节,payload 内出现的 0x7D 不影响帧同步;
      仅 IDLE 状态寻找 HEAD;SUM 校验失败 / 超长帧 → 回 IDLE 丢弃。
]]

-- 加载配置
local CFG = require "config"

local UART_ID   = CFG.CFG_UART_ID
local MAX_LEN   = CFG.CFG_FRAME_MAXLEN

-- ==================== 接收状态机 ====================
local RX_IDLE, RX_HEAD, RX_LENH, RX_LENL, RX_DATA, RX_SUM = 0, 1, 2, 3, 4, 5
local rx_state = RX_IDLE
local rx_len = 0        -- 当前帧 PAYLOAD 长度
local rx_buf = ""       -- PAYLOAD 缓冲
local rx_sum = 0        -- 累加和(覆盖 HEAD 起所有字节)

local function rx_reset()
    rx_state = RX_IDLE
    rx_len = 0
    rx_buf = ""
    rx_sum = 0
end

-- 一帧完整且校验通过 → 发布到 MQTT 发送队列
local function on_frame_ok(payload)
    log.info("uart_app.frame", "len", payload:len())
    -- SEND_DATA_REQ(tag, topic, payload, qos)
    -- 上行统一发布到 dev 主题(平台侧与有线通道无差别)
    sys.publish("SEND_DATA_REQ", "vd960DBN", CFG.CFG_TOPIC_UP, payload, 1)
end

-- 逐字节喂入接收状态机
local function feed_byte(b)
    if rx_state == RX_IDLE then
        if b == CFG.CFG_FRAME_HEAD then
            rx_state = RX_HEAD
            rx_sum = b
        end
    elseif rx_state == RX_HEAD then
        rx_len = b * 256
        rx_sum = (rx_sum + b) % 256
        rx_state = RX_LENH
    elseif rx_state == RX_LENH then
        rx_len = rx_len + b
        rx_sum = (rx_sum + b) % 256
        if rx_len > MAX_LEN then
            log.warn("uart_app.feed", "frame too long", rx_len)
            rx_reset()
        else
            rx_buf = ""
            rx_state = RX_LENL
        end
    elseif rx_state == RX_LENL then
        -- 0 长度帧非法
        if rx_len == 0 then
            rx_reset()
        else
            rx_state = RX_DATA
        end
    elseif rx_state == RX_DATA then
        rx_buf = rx_buf .. string.char(b)
        rx_sum = (rx_sum + b) % 256
        if rx_buf:len() >= rx_len then
            rx_state = RX_SUM
        end
    elseif rx_state == RX_SUM then
        if b == rx_sum then
            on_frame_ok(rx_buf)
        else
            log.warn("uart_app.feed", "checksum fail")
        end
        rx_reset()
    end
end

-- UART1 接收中断处理
local function read()
    local s
    while true do
        s = uart.read(UART_ID, 1024)
        if not s or s:len() == 0 then
            break
        end
        for i = 1, s:len() do
            feed_byte(string.byte(s, i))
        end
    end
end

-- ==================== 下行: MQTT → UART1 ====================
-- mqtt_receiver 发布 RECV_DATA_FROM_SERVER(topic, payload)
local function recv_data_from_server_proc(topic, payload)
    if not payload or payload:len() == 0 then
        return
    end
    -- 组帧: HEAD + LEN(2B BE) + PAYLOAD + SUM
    local len = payload:len()
    local frame = string.char(CFG.CFG_FRAME_HEAD)
        .. string.char(math.floor(len / 256)) .. string.char(len % 256)
        .. payload
    local sum = CFG.CFG_FRAME_HEAD
    sum = (sum + math.floor(len / 256)) % 256
    sum = (sum + len % 256) % 256
    for i = 1, len do
        sum = (sum + string.byte(payload, i)) % 256
    end
    frame = frame .. string.char(sum)
    uart.write(UART_ID, frame)
    log.info("uart_app.down", "len", len)
end

-- ==================== 初始化 ====================
uart.setup(UART_ID, CFG.CFG_UART_BAUD, 8, 1)
uart.on(UART_ID, "receive", read)
sys.subscribe("RECV_DATA_FROM_SERVER", recv_data_from_server_proc)

log.info("uart_app", "init ok", "baud", CFG.CFG_UART_BAUD, "topic_up", CFG.CFG_TOPIC_UP)