Hardware development notes (III): basic process of hardware development, making a USB to RS232 module (II): design principle diagram Library

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Hardware related development

Last one ：《 Hardware development notes （ Two ）： Basic process of hardware development , To make a USB turn RS232 Module （ One ）： Basic development process and component selection 》
Next ：《 Hardware development notes （ Four ）： Basic process of hardware development , To make a USB turn RS232 Module （ 3、 ... and ）： Schematic design 》

Preface

   In the previous article, I learned about the basic process , Relevant chips are selected , This chapter describes the design process of schematic diagram , Before or in the process of schematic design, it is necessary to continuously add schematic elements and devices .

Allegro、OrCad

  Cadence The company aims at PCB Aspect EDA Products can be roughly divided into high-end and low-end , High end is Cadence SPB, The low end is OrCAD.
   No matter high-end or low-end , The schematic part is mainly purchased OrCAD Schematic software in （ It's called Capture）.
  PCB The drawing is different , High-end Cadence SPB It's called Allegro, Low-end OrCAD Now it mainly uses Allegro A simplified version of the , Will contain the complete PSpice（ Circuit simulation software ）.

OrCad Design schematic library

   When designing the schematic diagram , It is necessary to establish the basic identification graphics of components , Some come with them , Some are provided by the government or suppliers , There are also , We choose to build our own （ Mainly describe the process ）.

Step one ： start-up OrCad

  
  （ Be careful ： yes Capture CIS, No separate Cadence OrCad Icon ）.
  
  
  

Step two ： New project usbTtlRs232

  
  
  

Step three ： Adjust the window layout

   Adjust the window distribution ：
  
  
   Maybe the software is old , Didn't like VS That kind of automatic layout , When the main window is zoomed , The child window will not be scaled ：
  
  
   Manual adjustment ：
  
  

Step four ： Modify properties and versions

  
   Double click the pop-up attribute box to modify ：
  
   Change the version number ：
  
  

Step five ： Library file import

  OrCad I brought some libraries with me , In the installation directory ：
  
  
   Library description view ：《 Hardware practical skills ：OrCad Built in schematic diagram olb/OLB Introduction to library enumeration 》
   Common components , I like to build my own database .

Step six ： Establish schematic Library

  （ Delete the introduced ）.
  
   Has generated ：
  
   Modify name ：
  
   Modified ：
  

Step seven ： Add new components and place

USB（ Male head ）

   On the schematic diagram , You can choose to show it , You can also choose not to be obvious , Finally, the schematic diagram is needed lib And pcb Of lib For pin mapping decisions .
  
  
  
   The tools are as follows ：
  
  
   Select schematic , Then place the components ：
  
  

ASM1117

  
  

2.54mm DIP

  

CH340G

   Typical circuits recommended in the manual ：
  
   Pins not drawn , All are suspended by default ：
  

MAX232

   Refer to the circuit diagram on the screenshot of the manual above to draw ：
  

Crystal oscillator

  

  
  
  
  

Step eight ： All schematic libraries are placed on the schematic

  
  

Last one ：《 Hardware development notes （ Two ）： Basic process of hardware development , To make a USB turn RS232 Module （ One ）： Basic development process and component selection 》
Next ：《 Hardware development notes （ Four ）： Basic process of hardware development , To make a USB turn RS232 Module （ 3、 ... and ）： Schematic design 》