# UART：CTS流控制超时，USART2上传输停滞

- **ID:** `embedded/uart-cts-flow-control-timeout`
- **领域:** embedded
- **类别:** communication_error
- **错误码:** `0x00020001`
- **验证级别:** ai_generated
- **修复率:** 89%

## 根因

UART CTS（清除发送）线被远程设备拉高或因硬件故障卡住，导致发送器无限期等待。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| STM32F405 HAL 1.8.0 | active | — | — |
| Zephyr RTOS 3.6.0 | active | — | — |

## 解决方案

1. ```
   Implement CTS timeout in firmware: if (HAL_UART_GetState(&huart2) == HAL_UART_STATE_BUSY_TX) { HAL_UART_Abort(&huart2); HAL_UART_Transmit_IT(&huart2, pData, Size); }
   ```
2. ```
   Add a pull-down resistor on CTS line to force low in case of floating signal; measure CTS voltage with oscilloscope.
   ```

## 无效尝试

- **** — Disabling hardware flow control entirely may cause data loss; it is not a fix for CTS timeout but a workaround that changes protocol. (75% 失败率)
- **** — Increasing UART baud rate does not resolve CTS line stuck high; the issue is external signal, not internal timing. (90% 失败率)