我想用CH340做一个简单的工具，单片机和上位机通信，单片机除了和CH340通信，还可以传递出两个低电平信号，我想用CH340得到这两个低电平信号，但不知道上位机如何检测到传递过来的信号，应该用到的是CTS#和DSR#，请指导下在上位机程序中如何检测CTS#和DSR#变为低电平！

到参看一下windows API 函数 GetCommModemStatus 的使用。

Syntax

BOOL WINAPI GetCommModemStatus(
  __in   HANDLE hFile,
  __out  LPDWORD lpModemStat);

Parameters

• hFile

• A handle to the communications device. The CreateFile function returns this handle.

• lpModemStat

• A pointer to a variable that receives the current state of the modem control-register values. This parameter can be one or more of the following values.

  ValueMeaning

  MS_CTS_ON
  0x0010

  The CTS (clear-to-send) signal is on.

  MS_DSR_ON
  0x0020

  The DSR (data-set-ready) signal is on.

  MS_RING_ON
  0x0040

  The ring indicator signal is on.

  MS_RLSD_ON
  0x0080

  The RLSD (receive-line-signal-detect) signal is on.