WEEK 8 - Electronics Design
Checklist:
- Use an EDA tool to design a development board to interact and communicate with an embedded microcontroller.
Learnings from the group assignment
The group work involved using a multimeter and an oscilloscope to understand which signals to measure to verify the operation of a PCB board.
Design process and Result
Choosing the Microcontroller
First, it was necessary to decide which software to use to start designing the microcontroller PCB. Then, I decided which microcontroller to use for the design. In this case, I want to use an ATmega328P or an ATTiny442. To do this, I prepared a comparative of the most relevant characteristics:
Preparing EDA Software
After the group meeting, it was agreed to use Eagle software because it is embedded in Fusion 360 and also because it is the most versatile, theoretically allowing the generation of G code for PCB machining.
First, it was necessary to download Fusion 360 software using my educational account to gain access. I visited the (Autodesk student website), registered my account with the university domain (@ulima.edu.pe), and downloaded the program.
To start with the first step, which is the schematic design, it is necessary to download the component libraries used in Fab Academy. For this, I visited the main website of the week and accessed the (GitLab link) and downloaded the Eagle library.
I downloaded the code as a .zip file and saved it in my resources folder. To keep everything organized, I created a FAB LAB UL workgroup in which I created a project called Fab Academy 2024.
Importing Fab Academy Library
To enter the Eagle module, you need to create a library file. To do this, click on the file icon and select the "New Electronics Library" option:
Then, click on the "Import Libraries" icon and select the "Import from local disk" option:
Once in that menu, you should copy the "fab.lbr" file that we downloaded from GitLab into the folder path "libraries".
Verify that it has been added by entering the "Source" filter and selecting the "Local disk" checkbox:
Electronic design
Schematic Design
To enter the Eagle module, you need to create a circuit file. To do this, click on the file icon and select the "New Electronics Design" option:
Then, create a schematic to design the connections of the PCB board by selecting the "New Schematic" icon.
In the search tab, choose each component one by one and place them in the design area.
To place the component in the design area, you can double-click or click and drag the component. To rotate it, right-click.
PCB Design
To facilitate the identification of the pins when fabricating the board, I placed the numbers or names of the pins associated with the 6x2 headers.
PCB Simulation
If the maximum impedance value obtained from my simulation for the longest track is 202.9 ohms, it means that the track impedance is relatively high. For low-speed signals, this may not be a significant problem, as signal integrity may not be significantly affected by impedance variations.
However, if I am designing for high-speed signals or have specific concerns about signal integrity, I may consider adjusting the track design to reduce impedance. This could be achieved by modifying the track width, spacing between tracks.
It is important to remember that the maximum acceptable impedance value may vary depending on my specific application and system requirements. If I am satisfied with the signal performance in my current design and am not experiencing signal integrity issues, I may not need to make additional adjustments to the track impedance. I will verify this when I fabricate and test it.
Export for Manufacturing
The board can be machined from the "Manufacturing" tab of the same software, but to expedite the testing process, I will use DXF and enable machining using Aspire. To do this, I go to the option Manufacturing > CAM Preview:
Result
Final Schematic
Final PCB
