将串口DB9中的RTS和CTS、DSR、DTR引脚用作一般的IO口来控制继电器/LED或者其他硬件

以前用串口从来只接了235脚, 其他脚没去留意过.

这次有个特殊需求, 正常情况下需要一个外部IO口控制一个设备的开关断 , 如果是之前我会弄个单片机或者从其他地方引根线过来用.

这次搜索发现串口其他脚太浪费了, 搜索才知道还可以当io用啊

具体一点就是:

Rts 和 Dtr 引脚可以用作 输出 功能

Dsr 和 Cts 引脚可以用作 输入 功能

在c#中代码控制代码如下:

serialPort1.RtsEnable = true;//将 RTS 输出高电平
serialPort1.DtrEnable = true;//将 DTR 输出高电平
var dSr_Staus = serialPort1.DsrHolding;//获取 DSR 输入高低电平状态
var cTs_Staus = serialPort1.CtsHolding;//获取 CTS 输入高低电平状态

我这里做了个简单的控制led灯的示意图.

控制程序如下:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            serialPort1.PortName = textBox1.Text;
            serialPort1.BaudRate = 115200;
            serialPort1.Open();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            serialPort1.RtsEnable = true;
        }

        private void button3_Click(object sender, EventArgs e)
        {
            serialPort1.RtsEnable = false;
        }
    }
}

RtsEnable就是控制IO的高低电平的, 电压是看串口的芯片的, ft232好像是±7V , PL2303是±9V输出.

视频如下:

另外, 这些引脚状态也是可以监听的, 有相应的回调事件,

可以参考文章: C# SerialPinChange A ring indicator was detected. (demo2s.com)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.IO.Ports;
using System.IO.Pipes;
namespace SerialPortPushButton
{
    class Program
    {
        static SerialPort p; static StreamWriter sw; static string version; static bool prevState; static void Main(string[] args)
        {
            version = System.Reflection.Assembly.GetExecutingAssembly().GetName().Version.ToString();
            NamedPipeClientStream pipeClient = new NamedPipeClientStream(".", "TIMclk", PipeDirection.Out);
            Console.Write("Attempting to connect to pipe... ");
            pipeClient.Connect();
            Console.WriteLine("Connected to pipe.");
            Console.WriteLine("There are currently {0} pipe server instances open.", pipeClient.NumberOfServerInstances); if (pipeClient.IsConnected == false)
            {
                Console.WriteLine("Pipe is not connected. Aborting. Please start Server first."); return;
            }
            sw = new StreamWriter(pipeClient);
            sw.AutoFlush = true; try
            {
                string sendtext = "SPPB-HELO:Serial Port Push Button Client version " + version;
                Console.WriteLine(sendtext);
                sw.WriteLine(sendtext);
            }
            catch (IOException e)
            {
                Console.WriteLine("ERROR: {0}", e.Message);
            }
            p = new SerialPort("COM10", 9600, Parity.None, 8, StopBits.One);
            p.RtsEnable = true;
            p.PinChanged += new SerialPinChangedEventHandler(myPinChanged); try
            {
                p.Open();
            }
            catch (Exception e)
            {
                Console.WriteLine("Cannot open Port. Try again. (Press Enter to quit) ...");
                Console.ReadLine(); return;
            }
            Console.WriteLine("Connected to COM1.");
            Console.ReadLine();
        }
        static void myPinChanged(object sender, SerialPinChangedEventArgs e)
        {
            TimeSpan tsNow = DateTime.Now.TimeOfDay; string info = string.Empty; switch (e.EventType)
            {
                case SerialPinChange.Break:
                    info = string.Format("Break detected. BreakState = {0}", p.BreakState); break;
                case SerialPinChange.CDChanged:
                    info = string.Format("Carrier Detect (CD) signal changed state. CD State = {0}", p.CDHolding); break;
                case SerialPinChange.CtsChanged:
                    info = string.Format("Clear to Send (CTS) signal changed state. CTS State = {0}", p.CtsHolding); break;
                case SerialPinChange.DsrChanged:
                    string statstr = p.DsrHolding == true ? "ON" : "OFF"; string writestr = "SPPB-EV:001 " + statstr + " " + tsNow.ToString(@"hh\:mm\:ss\,fff"); try
                    {
                        sw.WriteLine(writestr);
                        Console.WriteLine(writestr);
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine("ERROR ON: " + writestr);
                        Console.WriteLine(ex.ToString());
                    }
                    break;
                case SerialPinChange.Ring:
                    info = "Ring detected";
                    break;
                default: break;
            }
            Console.WriteLine(info); bool thisState = p.CDHolding; if (thisState == true && prevState == false)
            {
            }
        }
    }
}