LTC2873 - 具可通断终端的单总线 RS485 / RS232 多协议收发器

特点

  • 一个 RS485 或一个 RS232 收发器
  • 3V 5.5V 电源电压
  • 高达 20Mbps RS485
  • 转换控制型 RS232 操作:
              可选的 1Mbps 250kbps
  • 可自动选择集成型 RS485 (120Ω) RS232 (5kΩ) 终端电阻器
  • ESD±26kV HBM
  • 逻辑环回模式
  • 1.7V 至 5.5V 逻辑接口
  • 支持多达 256 个 RS485 节点
  • 全面防故障的 RS485 接收器消除了 UART 锁定
  • 可提供 H 级 (–40ºC 至 125ºC)
  • 采用 24 引脚 4mm x 5mm QFN 封装

典型应用

LTC2873 Typical Application
LTC2873 Typical Application

描述

LTC®2873 是一款坚固的引脚可配置型多协议收发器,可支持 RS232、RS485 和 RS422 协议,并采用单 3V 至 5.5V 工作电源。LTC2873 可配置为采用相同的两个总线引脚的一个半双工 RS485 收发器或一个 RS232 收发器。

一个通过引脚控制的集成型终端电阻器实现了简易的接口再配置,从而免除了外部电阻器和控制继电器。环回模式负责将驱动器输入引导至接收器输出以进行诊断性的自测试。RS485 接收器可在每根总线上支持多达 256 个节点,并执行针对浮动、短路或端接输入的全故障安全运作。

一个集成型 DC/DC 升压转换器采用一个纤巧的 2mm x 1.6mm 电感器和一个电容器,从而免除了在驱动 RS232 电平时增设多个电源的需要。

封装

如需了解完整与最新的封装信息及图例,请查阅我们的封装网页

器件型号 封装 Code 温度 封装图 RoHS 数据
LTC2873CUFD#PBF 4x5 QFN-24 UFD C 05-08-1696 Yes
LTC2873CUFD#TRPBF 4x5 QFN-24 UFD C 05-08-1696 Yes
LTC2873HUFD#PBF 4x5 QFN-24 UFD H 05-08-1696 Yes
LTC2873HUFD#TRPBF 4x5 QFN-24 UFD H 05-08-1696 Yes
LTC2873IUFD#PBF 4x5 QFN-24 UFD I 05-08-1696 Yes
LTC2873IUFD#TRPBF 4x5 QFN-24 UFD I 05-08-1696 Yes


LTC2873 Package Drawing

订购信息

  • 以 PBF 结尾的器件型号表示这些是无铅型器件。如需了解有关含铅涂层器件的信息,请与凌力尔特公司联系。

  • 型号当中包含 TR 或 TRM 的器件分别采用卷带装500 片微型卷带装的形式进行装运。

  • 如需了解更多的细节,请查阅我们一般订购信息或产品数据手册。

各种封装型式和定价

器件型号 封装 温度 价格 (以 1 ~ 99 片为批量) 价格 (以 1000 片为批量) * RoHS 数据
LTC2873CUFD#PBF 4x5 QFN-24 C $6.36 $4.45 Yes
LTC2873CUFD#TRPBF 4x5 QFN-24 C $6.42 $4.51 Yes
LTC2873HUFD#PBF 4x5 QFN-24 H $8.41 $5.89 Yes
LTC2873HUFD#TRPBF 4x5 QFN-24 H $8.47 $5.95 Yes
LTC2873IUFD#PBF 4x5 QFN-24 I $7.31 $5.12 Yes
LTC2873IUFD#TRPBF 4x5 QFN-24 I $7.37 $5.18 Yes
购买要求提供样品

* 美国价目表所列之价格仅供预算之用,单位为美元 (针对规定批量的美国 FOB 单价),随时可能变更。国际销售价格有可能因为地方税额、费用和汇率而有所不同。如需了解特定批量的价格或货运报价,请您与凌力尔特当地的销售办事处或授权分销商联系

演示电路板

凌力尔特的演示电路板可免费提供给合资格的客户,请您与当地的销售办事处或分销商联系,申请获取演示电路板。另外,某些演示电路板也可通过信用卡在此网站上购买。演示电路板仅供评估之用。器件在实际终端应用中的正确与可靠运作的验证仍然是客户的责任。

器件型号 描述 价格 Documentation
DC2364A LTC2873 Demo Board | Single Bus RS232/RS485 Multiprotocol Transceiver with Integrated Termination (Shared I/O) (DC2026 optional) $25.00
购买

Companion Boards

器件型号 描述 价格 Documentation
DC2026C Linduino One Isolated USB Demo Board: An Arduino- and QuikEval-Compatible Code Development Platform $75.00
购买
点击这里查看我们的演示板完整列表

应用

  • 可利用软件选择的 RS232 / RS485 / RS422 接口
  • 工业传感器和执行器
  • 报警系统
  • 交通管理和监测
  • 公路标志和大屏幕显示

产品通知

请登录您的 MyLinear 帐户,以获得数据表更新通知、新文档发布、以及针对您喜爱产品的 LTspice 模型通告。 如果您还没有 MyLinear 帐户,可以立即 注册

忘记密码吗? 请单击这里
需要帮助吗? 如果有任何问题或意见,请发送电子邮件至 mylinear@linear.com

设计工具

Linduino

Linduino 是一款可兼容 Arduino 的平台,其用于开发和分配用于 SPI 和 I2C 兼容型集成电路的固件库和代码。Linduino One 电路板可连接 300 多款 QuikEval 演示板卡并支持多种产品类型,包括模数转换器 (ADC)数模转换器 (DAC)功率监视器等等。用于个别器件的固件库采用 C 语言编写并专为可移植到众多的处理器和微控制器而设计。每个固件库具有一种演示程序,此演示程序可上载至 Linduino One 平台以简便快捷地完成电路和软件的验证。

点击这里以了解 Linduino 的更多相关信息

 

代码

Linduino 是凌力尔特的 Arduino 兼容型系统,适用于开发和分发针对凌力尔特集成电路的固件库和代码范例。下面的代码程序可以下载或者“拷贝并粘贴”到您的设计方案之中。请访问 Linduino 主页以获取演示板、手册和设置信息。

该器件得到了代码支持: 提供了可用于该器件的代码示例。下面的代码有可能依存于完整库中提供的其他驱动程序。

Download LTC2873 - DC2364A.ino

/*!
Linear Technology DC2364A Demonstration Board with SPI interface.
LTC2873: Two-Wire RS485/RS232 Transceiver with Switchable Termination.

@verbatim

NOTES
  Setup:
   Set the terminal baud rate to 115200 and select the newline terminator.
   Ensure all jumpers on the demo board are installed in their default positions
   from the factory. Refer to Demo Manual DC2364A.

  How to test:


USER INPUT DATA FORMAT:
 decimal : 1024
 hex     : 0x400
 octal   : 02000  (leading 0 "zero")
 binary  : B10000000000
 float   : 1024.0

@endverbatim
http://www.linear.com/product/LTC2873

REVISION HISTORY
$Revision: 4437 $
$Date: 2015-12-01 08:26:42 -0800 (Tue, 01 Dec 2015) $

Copyright (c) 2013, Linear Technology Corp.(LTC)
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies,
either expressed or implied, of Linear Technology Corp.

The Linear Technology Linduino is not affiliated with the official Arduino team.
However, the Linduino is only possible because of the Arduino team's commitment
to the open-source community.  Please, visit http://www.arduino.cc and
http://store.arduino.cc , and consider a purchase that will help fund their
ongoing work.
*/

//! @defgroup LTC2873 LTC2873: Two-Wire RS485/RS232 Transceiver with Switchable Termination.

/*! @file
    @ingroup LTC2873
    Library for LTC2873: Two-Wire RS485/RS232 Transceiver with Switchable Termination.
*/

// Headerfiles
#include <UserInterface.h>  // LTC defined
#include <SoftwareSerial.h>

//! @name Assigned Pin Numbers
//! @{
#define RO              10 // soft UART with interrupt pin.  (SSerial RX)
#define DI              11 // soft UART with interrupt pin   (SSerial TX)
#define DE485_F232      3  // RE485B jumpered to here.  (SSerialTxControl)
#define RE485b          4  // beware of jumper tying to DE485
#define MODE485         5  // "select" RS485 if high, 232 if low.
#define TE485b          6  //  RS485 termination enable BAR
#define LB              7  // Loopback 232 or 485
#define SHDNb           2  // Shutdown BAR
//!@}

// Global Variables
int byteReceived;
int byteSend;
int di_toggle = 0;
int SDNb_val, MODE485_val, REb_val, DE485_F232_val, TEb_val, LB_val, DI_val;

//! Initialize Linduino
void setup()
{
  // Set pin directions
  pinMode(RO, INPUT_PULLUP);
  pinMode(DI, OUTPUT);
  pinMode(DE485_F232, OUTPUT);
  pinMode(RE485b, OUTPUT);
  pinMode(MODE485,OUTPUT);
  pinMode(TE485b,OUTPUT);
  pinMode(LB,OUTPUT);
  pinMode(SHDNb,OUTPUT);

  // Initialize pins
  digitalWrite(DI,LOW);
  digitalWrite(DE485_F232,LOW);
  digitalWrite(RE485b,HIGH);
  digitalWrite(MODE485,HIGH);
  digitalWrite(TE485b,HIGH);
  digitalWrite(LB,LOW);
  digitalWrite(SHDNb,LOW);

  TCCR2B = TCCR2B & 0b11111000 | 0x01;    // set PWM freq to 31372.55Hz (and scales timers!)
  //TCCR2B = TCCR2B & 0b11111000 | 0x04;  // set PWM freq on pins 2, 11 to 490.20Hz (default)

  // Open communications to serial monitor
  Serial.begin(115200);               // DON'T FORGET TO SET SERIAL MONITOR TO THIS SPEED!!!
  // RS485Serial.begin(4800);           // Start the software serial port, to another device
  print_title();                      // Menu on serial monitor
  print_status();
}

//! Repeats Linduino loop
void loop()
{
  uint8_t user_command = read_int();
  Serial.print(F("    "));

  if (user_command > 0 && user_command < 27)
  {
    update(user_command);
    Serial.print(user_command);
    print_status();             // Print status after operation
  }
  else if (user_command == 'm')
  {
    update(user_command);
    Serial.print(F("m"));
    print_status();             // Print status after operation
  }
  else
  {
    Serial.println(F("Wrong choice. TRY AGAIN!"));
  }
}

//! Prints the title block when program first starts.
void print_title(void)
{
  Serial.println(F(" "));
  Serial.println(F("**************************************************************************"));
  Serial.println(F("DC2364A Demonstration Board for the LTC2873 "));
  Serial.println(F("**************************************************************************"));
  Serial.println(F("PIN CONTROL:             MODES:"));
  Serial.println(F("1. Flip SHDNb            10. Shutdown               19. 485 Term"));
  Serial.println(F("2. Flip 485/232b         11. 232 RX+TX Slow         20. 485 RX+Term"));
  Serial.println(F("3. Flip RE485b           12. 232 RX+TX Fast         21. 485 TX+Term"));
  Serial.println(F("4. Flip DE485/F232       13. 232 Loopbk+TX Slow     22. 485 RX+TX+Term"));
  Serial.println(F("5. Flip TE485b           14. 232 Loopbk+TX Fast     23. 485 Loopbk"));
  Serial.println(F("6. Flip LB               15. 485 Ready              24. 485 Loopbk+TX"));
  Serial.println(F("7. Flip DI               16. 485 RX                 25. 485 Loopbk+Term"));
  Serial.println(F("8. 31.4kHz 50% on DI*    17. 485 TX                 26. 485 Loopbk+TX+Term"));
  Serial.println(F("9. 31.4kHz 10% on DI*    18. 485 RX+TX "));
  Serial.println(F("**************************************************************************"));
  Serial.println(F("Press m to stop 31.4 kHz signal "));
  Serial.println(F(" "));
  Serial.println(F("CURRENT STATE:"));
  Serial.println(F("User Entry    SHDNb    485   RE485b   DE485   TE485b    LB      DI      MODE"));
  Serial.println(F("-----------------------------------------------------------------------------"));
  Serial.print(F("    "));
}

//! Prints the status of each pin based on user selection.
void print_status(void)
{
  SDNb_val = digitalRead(SHDNb);
  MODE485_val = digitalRead(MODE485);
  REb_val = digitalRead(RE485b);
  DE485_F232_val = digitalRead(DE485_F232);
  TEb_val = digitalRead(TE485b);
  LB_val = digitalRead(LB);

  Serial.print(F("\t\t"));
  Serial.print(SDNb_val, DEC);
  Serial.print(F("\t"));
  Serial.print(MODE485_val, DEC);
  Serial.print(F("\t"));
  Serial.print(REb_val, DEC);
  Serial.print(F("\t"));
  Serial.print(DE485_F232_val, DEC);
  Serial.print(F("\t"));
  Serial.print(TEb_val, DEC);
  Serial.print(F("\t"));
  Serial.print(LB_val, DEC);
  Serial.print(F("\t"));

  if (di_toggle)             // must check if pwm mode to preserve, otherwise, digitalRead will kill it.
  {
    Serial.print("pwm");
  }
  else                       // not pwm'ing it.
  {
    DI_val = digitalRead(DI);
    Serial.print(DI_val,DEC);
  }
  Serial.print(F("\t"));

  String status_val = status();
  // String status_val = find_status();
  Serial.print(status_val);
  Serial.print(F("\n"));
}

//! Returns a descriptive string based on status of pins.
String status(void)
{
  if (!SDNb_val)
    return "SHUTDOWN";
  if (!MODE485_val && !DE485_F232_val && !LB_val)
    return "232 RX+TX SLOW";
  if (!MODE485_val && !DE485_F232_val && LB_val)
    return "232 LB+TX SLOW";
  if (!MODE485_val && DE485_F232_val && !LB_val)
    return "232 RX+TX FAST";
  if (!MODE485_val && DE485_F232_val && LB_val)
    return "232 LB+TX FAST";
  if (MODE485_val && !DE485_F232_val && REb_val && TEb_val && !LB_val)
    return "485 READY  ";
  if (MODE485_val && !DE485_F232_val && REb_val && !TEb_val && !LB_val)
    return "485 TERM  ";
  if (MODE485_val && DE485_F232_val && REb_val && TEb_val && !LB_val)
    return "485 TX    ";
  if (MODE485_val && DE485_F232_val && REb_val && !TEb_val && !LB_val)
    return "485 TX+TERM";
  if (MODE485_val && !DE485_F232_val && !REb_val && TEb_val && !LB_val)
    return "485 RX    ";
  if (MODE485_val && !DE485_F232_val && !REb_val && !TEb_val && !LB_val)
    return "485 RX+TERM";
  if (MODE485_val && DE485_F232_val && !REb_val && TEb_val && !LB_val)
    return "485 RX+TX";
  if (MODE485_val && DE485_F232_val && !REb_val && !TEb_val && !LB_val)
    return "485 RX+TX+TERM";
  if (MODE485_val && !DE485_F232_val && !REb_val && TEb_val && LB_val)
    return "485 LB    ";
  if (MODE485_val && !DE485_F232_val && !REb_val && !TEb_val && LB_val)
    return "485 LB+TERM";
  if (MODE485_val && DE485_F232_val && !REb_val && TEb_val && LB_val)
    return "485 LB+TX";
  if (MODE485_val && DE485_F232_val && !REb_val && !TEb_val && LB_val)
    return "485 LB+TX+TERM";
}

//! Returns a descriptive string based on status of pins.
String find_status(void)
{
  String status = "";
  if (!SDNb_val)
    status = status + "SHUTDOWN";
  else
  {
    if (MODE485_val)
    {
      status = status + "485 ";
      if (DE485_F232_val)
        status = status + "ENABLE ";
      else
        status = status + "DISABLE ";
    }
    else
    {
      status = status + "232 ";
      if (DE485_F232_val)
        status = status + "FAST ";
      else
        status = status + "SLOW ";
    }

    if (LB_val)
      status = status + "LB ";
    if (!REb_val)
      status = status + "RX ";
    if (DE485_F232_val)
      status = status + "TX ";

    if (!TEb_val)
      status = status + "TERM ";
  }
  return status;
}

//! Function to toggle the state of a pin.
void flipPin(uint8_t pin)
{
  int pinValue = digitalRead(pin);
  if (pinValue)         // if pin is high
    digitalWrite(pin, LOW);     // change to low
  else
    digitalWrite(pin, HIGH);    //otherwise, set high
}

//! Update the state of pins based on user selection.
void update(uint8_t user_command)
{
  switch (user_command)
  {
    case 1:
      {
        // Flip SHDNb
        flipPin(SHDNb);
        break;
      }
    case 2:
      {
        // Flip 485/232b
        flipPin(MODE485);
        break;
      }
    case 3:
      {
        // Flip RE485b
        flipPin(RE485b);
        break;
      }
    case 4:
      {
        // Flip DE485/F232
        flipPin(DE485_F232);
        break;
      }
    case 5:
      {
        // Flip TE485b
        flipPin(TE485b);
        break;
      }
    case 6:
      {
        // Flip LB
        flipPin(LB);
        break;
      }
    case 7:
      {
        // Flip DI
        di_toggle=0;                // clear the toggle variable so the status will print correctly
        flipPin(DI);
        break;
      }
    case 8:                    // pwm on DI.  Freq set by TCCR2B at top
      {
        // 31.4kHz 50% on DI*
        analogWrite(DI,128);     // 25% duty cycle is between  0 and 255
        di_toggle = 1;           // set flag for reporting status on this bit
        break;
      }
    case 109:          // 120 = 'x'
      {
        analogWrite(DI,0);       // Stop 31.4 kHz signal
        di_toggle = 0;           // set flag for reporting status on this bit
        break;
      }
    case 9:                    // pwm on DI.  Freq set by TCCR2B at top
      {
        // 31.4kHz 10% on DI*
        analogWrite(DI,26);      // 10% duty cycle is between  0 and 255
        di_toggle = 1;           // set flag for reporting status on this bit
        break;
      }
    case 10:
      {
        //SHUTDOWN
        digitalWrite(SHDNb,LOW);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,HIGH);
        digitalWrite(DE485_F232,LOW);
        digitalWrite(TE485b,HIGH);
        digitalWrite(LB,LOW);
        //digitalWrite(DI,LOW);
        break;
      }
    case 11:
      {
        //232 RX + TX SLOW
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,LOW);
        digitalWrite(RE485b,HIGH);
        digitalWrite(DE485_F232,LOW);
        digitalWrite(TE485b,HIGH);
        digitalWrite(LB,LOW);
        //digitalWrite(DI,LOW);
        break;
      }
    case 12:
      {
        //232 RX + TX FAST
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,LOW);
        digitalWrite(RE485b,HIGH);
        digitalWrite(DE485_F232,HIGH);
        digitalWrite(TE485b,HIGH);
        digitalWrite(LB,LOW);
        //digitalWrite(DI,LOW);
        break;
      }
    case 13:
      {
        //232 LOOPBACK + TX SLOW
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,LOW);
        digitalWrite(RE485b,HIGH);
        digitalWrite(DE485_F232,LOW);
        digitalWrite(TE485b,HIGH);
        digitalWrite(LB,HIGH);
        //digitalWrite(DI,LOW);
        break;
      }
    case 14:
      {
        //232 LOOPBACK + TX FAST
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,LOW);
        digitalWrite(RE485b,HIGH);
        digitalWrite(DE485_F232,HIGH);
        digitalWrite(TE485b,HIGH);
        digitalWrite(LB,HIGH);
        //digitalWrite(DI,LOW);
        break;
      }
    case 15:
      {
        //485 READY
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,HIGH);
        digitalWrite(DE485_F232,LOW);
        digitalWrite(TE485b,HIGH);
        digitalWrite(LB,LOW);
        //digitalWrite(DI,LOW);
        break;
      }
    case 16:
      {
        //485 RX
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,LOW);
        digitalWrite(DE485_F232,LOW);
        digitalWrite(TE485b,HIGH);
        digitalWrite(LB,LOW);
        //digitalWrite(DI,LOW);
        break;
      }
    case 17:
      {
        //485 TX
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,HIGH);
        digitalWrite(DE485_F232,HIGH);
        digitalWrite(TE485b,HIGH);
        digitalWrite(LB,LOW);
        //digitalWrite(DI,LOW);
        break;
      }
    case 18:
      {
        //485 RX + TX
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,LOW);
        digitalWrite(DE485_F232,HIGH);
        digitalWrite(TE485b,HIGH);
        digitalWrite(LB,LOW);
        //digitalWrite(DI,LOW);
        break;
      }
    case 19:
      {
        //485 TERMINATION
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,HIGH);
        digitalWrite(DE485_F232,LOW);
        digitalWrite(TE485b,LOW);
        digitalWrite(LB,LOW);
        //digitalWrite(DI,LOW);
        break;
      }
    case 20:
      {
        //485 RX + TERMINATION
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,LOW);
        digitalWrite(DE485_F232,LOW);
        digitalWrite(TE485b,LOW);
        digitalWrite(LB,LOW);
        //digitalWrite(DI,LOW);
        break;
      }
    case 21:
      {
        //485 TX + TERMINATION
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,HIGH);
        digitalWrite(DE485_F232,HIGH);
        digitalWrite(TE485b,LOW);
        digitalWrite(LB,LOW);
        //digitalWrite(DI,LOW);
        break;
      }
    case 22:
      {
        //485 RX + TX + TERMINATION
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,LOW);
        digitalWrite(DE485_F232,HIGH);
        digitalWrite(TE485b,LOW);
        digitalWrite(LB,LOW);
        //digitalWrite(DI,LOW);
        break;
      }
    case 23:
      {
        //485 LOOPBACK
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,LOW);
        digitalWrite(DE485_F232,LOW);
        digitalWrite(TE485b,HIGH);
        digitalWrite(LB,HIGH);
        //digitalWrite(DI,LOW);
        break;
      }
    case 24:
      {
        //485 LOOPBACK + TX
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,LOW);
        digitalWrite(DE485_F232,HIGH);
        digitalWrite(TE485b,HIGH);
        digitalWrite(LB,HIGH);
        //digitalWrite(DI,LOW);
        break;
      }
    case 25:
      {
        //485 LOOPBACK + TERM
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,LOW);
        digitalWrite(DE485_F232,LOW);
        digitalWrite(TE485b,LOW);
        digitalWrite(LB,HIGH);
        //digitalWrite(DI,LOW);
        break;
      }
    case 26:
      {
        //485 LOOPBACK + TX + TERM
        digitalWrite(SHDNb,HIGH);
        digitalWrite(MODE485,HIGH);
        digitalWrite(RE485b,LOW);
        digitalWrite(DE485_F232,HIGH);
        digitalWrite(TE485b,LOW);
        digitalWrite(LB,HIGH);
        //digitalWrite(DI,LOW);
        break;
      }

  }
}

技术支持