UART 透传

透传桥接 — UART over BLE — BLE GATT Notify/Write、UART 驱动、消息队列、双向透传

前置阅读：Hello BLE 基础入门三部曲（Hello BLE、Hello Notify、Hello ReadWrite）

学习目标

• 理解 BLE 双向透传的完整数据流
• 掌握消息队列在解耦 UART ISR 与 BLE 发送中的作用
• 理解 BLE MTU 对吞吐量的影响
• 能够在两块 WS63 之间实现双向串口透传

规格与功能

规格项	Peripheral 端	Central 端
链路 A（P→C）	UART RX → BLE Notify → Central	notify_cb → UART TX
链路 B（C→P）	Write handler → UART TX	UART RX → BLE Write → Peripheral
UART 配置	115200 8N1	同
BLE MTU	247（BLE 4.2 最大）	同
消息队列	UART ISR → 队列 → BLE 发送任务	同

基本概念

双向数据流

flowchart LR
    subgraph PCA[PC_A]
    end
    subgraph P[WS63 Peripheral]
        PUART[UART]
    end
    subgraph C[WS63 Central]
        CUART[UART]
    end
    subgraph PCB[PC_B]
    end

    PCA <-->|串口| PUART
    CUART <-->|串口| PCB

    PUART -- "链路 A: BLE Notify" --> CUART
    CUART -- "链路 B: BLE Write" --> PUART

BLE 透传的吞吐量限制

参数	BLE	SLE
PHY 速率	1M	1M/2M/4M
MTU	247	520
典型连接间隔	30ms	12.5ms
有效吞吐量	~20-40 KB/s	~80-100 KB/s

BLE 透传的吞吐量天然低于 SLE——PHY 上限低、MTU 小、连接间隔通常更长。如果应用对吞吐要求高，考虑用 SLE。

涉及 API

API	谁调用	用途
uapi_uart_open/write/register_rx_callback	双方	UART 操作
gatts_notify()	Peripheral	推数据给 Central
gattc_write()	Central	写数据给 Peripheral
osal_msg_queue_create/write_copy/read_copy	双方	解耦 ISR 与任务（OS 基础）

案例操作指导

PC_A 串口输入 → PC_B 显示，PC_B 串口输入 → PC_A 显示。

关键配置

• UART：115200 8N1
• BLE MTU：247
• BLE 连接间隔：建议 15~30ms
• 消息队列深度：8

代码详解

Peripheral 端：UART RX → BLE Notify

// UART ISR 中写消息队列
static void uart_rx_isr(uint8_t *data, uint16_t len)
{
    osal_msg_queue_write_copy(g_uart_queue_id, data, len, OSAL_MSGQ_NO_WAIT);
    osal_sem_up(&g_uart_sem);  // 通知发送任务
}

// 发送任务中取队列 → BLE Notify
static int ble_send_task_handler(void *data)
{
    uint8_t buf[247];
    unsigned int buf_size;
    while (1) {
        osal_sem_down(&g_uart_sem);
        buf_size = sizeof(buf);
        osal_msg_queue_read_copy(g_uart_queue_id, buf, &buf_size, OSAL_MSGQ_WAIT_FOREVER);
        gatts_notify(g_conn_id, g_data_char_handle, buf, buf_size);
    }
}

Peripheral 端：Central Write → UART TX

static void write_request_cb(uint16_t conn_id, uint16_t char_handle,
                              uint8_t *data, uint16_t len)
{
    // 直接 UART 输出（数据量小时可以；大量数据建议走队列）
    uapi_uart_write(g_uart_handle, data, len);
    gatts_send_response(conn_id, char_handle, NULL, 0);
}

连接状态守护

static void conn_state_cb(uint16_t conn_id, bt_gap_conn_state_t state)
{
    if (state == DISCONNECTED) {
        g_conn_id = 0;
        // 清空未发送的队列数据，避免旧数据在重连后乱序发送
        flush_uart_queue();
    }
}

// 发送前检查
void ble_send(const uint8_t *data, uint16_t len)
{
    if (g_conn_id == 0) return;  // 未连接，丢弃
    gatts_notify(g_conn_id, g_data_char_handle, data, len);
}

---