Generally ECAD tools are not built to support collaborative features such as git in software programming. PSLab hardware is developed using an open source ECAD tool called KiCAD. It is a practice in the electronic industry to use hierarchical blocks to support collaboration. One person can work on a specific block having rest of the design untouched. This will support a workaround to have a team working on a one hardware design just like a software design. In PSLab hardware repository, many developers can work simultaneously using this technique without having any conflicts in project files.
Printed Circuit Board (PCB) designing is an art. The way the components are placed and how they are interconnected through different type of wires and pads, it is an art for hardware designing engineers. If they do not use auto-route, PCB design for the same schematic will be quite different from one another.
There are two major approaches in designing PCBs.
- Top Down method
- Bottom Up method
Any of these methods can be implemented in PSLab hardware repository to support collaboration by multiple developers at the same time.
Top Down Method
In this method the design is starting from the most abstract definitions. We can think of this as a black box with several wires coming out of it. The user is aware of how to use the wires and to which devices they need to be connected. But the inside of the black box is not visible. Then a designer can open up this box and break the design down to several small black boxes which can perform a subset of functionalities the bigger black box did. He can go on breaking it down to even smaller boxes and reach the very bottom where basic components are found such as transistors, resistors, diodes etc.
Bottom Up Method
In the bottom up method, the opposite approach of the top down method is used. Small parts are combined together to design a much bigger part and they are combined together to build up an even bigger part which will eventually create the final design. Our human body is a great example for a use of bottom up method. Cells create organ; organs create systems and systems create the body.
Designing Top Down Designs using KiCAD
In PCB designing, the designers are free to choose whatever the approach they prefer more suitable for their project. In this blog, the Top Down method is used to demonstrate how to create a design from the abstract concepts. This will illustrate how to create a design with one layer deep in design using hierarchical blocks. However, these design procedures can be carried out as many times as the designer want to create depending on the complexity of the project.
Step 01 – Create a new project in KiCAD
Step 02 – Open up Eeschema to begin the design
Step 03 – Create a Hierarchical Sheet
Step 04 – Place the hierarchical sheet on the design sheet and give it a name
Step 05 – Enter sheet
Step 06 – Place components and create a schematic design inside the sheet and place hierarchical labels
Step 07 – Define the labels as input or output and give them an identifier. Once done, place them on appropriate places and connect with wires
Step 08 – Go back to main sheet to complete the hierarchical block
Step 09 – Place hierarchical pins on the block
Click on the “Place hierarchical pin” icon from the toolbar and click on the block. The pins can be placed on anywhere on the block. As a convention, input pins are placed on the left side and the output pins are placed on the right side of the block.
Step 10 – Complete the circuit
- KiCAD Documentation – http://kicad-pcb.org/help/documentation/
- PSLab Hardware Repository – https://github.com/fossasia/pslab-hardware
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