AD20 study notes (three) schematic diagram and PCB drawing summary
The previous two articles briefly introduced the drawing method of the components and how to add packaging. This article mainly introduces some of the problems I encountered from the schematic drawing to the end of the drawing board and my corresponding solutions.
1. The schematic drawing process
introduced earlier that we don’t need to waste a lot of time to draw the component libraries and package libraries that need to be used in the drawing board sub-process. We only need to import the library files downloaded in advance (for specific import methods, please Refer to the previous article). The following is to find the corresponding component placement design circuit from the library file. Special attention here is to recognize the type of library file when looking for the corresponding device from the library file
- ".Intlib" is the suffix of the integrated library, the so-called integrated library is the integration of the schematic and PCB packaging
- ".Schlib" is only the schematic diagram, at this time you need to add the package manually (for specific adding methods, please refer to the previous article)
- ".Pcblib" is PCB packaging
problem 1 :
After drawing each circuit part of the schematic, you will find a red curve on each pin. This is because there is no pin definition. After the network label is placed, these red curves will automatically disappear.
Additional: Network label placement
Place —> Network label
Press Tab to modify the attributes of the network label.
Special attention: the network label should be placed on the line. When
placing it as shown in the figure, it means it is placed on the line.
Question 2: After
compiling the project, NETs has only one pin
directly translated is that some network tags only correspond to one pin. It is because some pins are not connected to the device. We only need to check our schematic diagram and modify it accordingly.
Question 3: After
compiling the project, Net xxx has no driving source is
directly translated as ***There is no driving source in the network xxx*** This kind of error is just a warning and will not have an impact, so we can ignore it. How to eliminate this warning I haven't tried yet, waiting for a more in-depth understanding later.
Question 4:
Extra pin xxx in Nomal of design item NPN appears after compiling the project. The
direct translation is the regular additional pin of the design project NPN. This is also a warning. I have this warning because a triode is placed in the schematic. I don't know the specific method and reason for eliminating it. I can only wait for more in-depth study later.
Question 5:
Floating net labels appear after compiling the project
According to the translation, it can be seen directly that a certain network label is still floating (it should be connected to the wire or pin). We only need to double-click the warning in the Messages dialog box to position the cursor on the problematic place and reposition the network label.
Note: If we don't want some warnings to report errors after compilation, we can set them. The specific setting method is as follows: Project-Project option selects its error as not to report
These are a few problems that I have encountered, and I may encounter more problems in the follow-up study. Then we will continue to summarize
2. PCB layout and wiring process.
First of all, we have to draw the outline of the board frame, you can use shortcut keys P+L, place a line, place a line and edit the origin as a reference point (Edit -> Origin -> Settings), and you can double-click the line to modify the line properties.
Then ctrl+A select the entire board frame design -> board shape -> define according to the selected object. The
final board frame is drawn. The
second step is to import the schematic library into the PCB package library. Design–>Import Changes From xxx–>Verify Changes–>Perform Changes
Note : If there is an error in verifying the changes and it may be due to packaging issues, you must return to the schematic to view the packaging of each component through the package manager. I encountered the problem caused by this package.
After successful import, it will be as shown in the figure.
Next is the layout and routing. At this time, we can turn off the extra window, leaving only ".SchDoc" (schematic diagram), and ".PcbDoc" (PCB) and window-> all windows disposed vertically, right ".PcbDoc" -.> Split vertically
so It is convenient for us to carry out the layout. At the same time, we must check the cross selection mode in the tool. The effect of checking here is that when we select a certain part of the circuit in the schematic diagram, the corresponding components in the PCB will be highlighted, which is very convenient for our layout. When laying out, the relevant devices should be placed as close as possible to facilitate subsequent wiring (I did not consider it during the layout, and the subsequent wiring was quite laborious).
After the layout is completed, start routing, and then you can close the schematic file. Observe the flying leads carefully before wiring. You can adjust the flying leads by pressing the space bar to rotate the components to minimize the crossing of the flying leads. Press and hold ctrl, double-click a device, the devices connected to the device will be highlighted, just connect to it. When the wiring on the top layer cannot be opened, we can route the wires on the bottom layer by placing vias. Before wiring, design the rules (Design -> Rules), set as shown in the figure
Note: The pin header is equivalent to a via hole, and the wire from the bottom layer can be directly connected to the pin header without adding another via hole to lead the wire back to the top layer. In addition, wires can also be routed under the components, and GND can be directly laid with copper without connecting
wires. After wiring is completed, click Tools -> Design Rule Check to perform DRC check and
click Run DRC. The problem here is mostly that the wire is too close or the wire is not connected to the pad. Just double-click the error message in the dialog box to locate the error and modify it accordingly.
3. Copper laying Copper
laying is the last step of PCB drawing. We can go through 1. Place -> Copper Paving. At this time, after we select the outer frame of the board, right-click to pave copper. Can also Tools -> Copper Shop - were> copper to copper shop manager
Note: To shop copper layers, top and bottom
case I encountered the problem here is to shop on copper wire, appeared as shown below
last , I created a new PCB with the help of my companion, then copied and pasted all the layout and wiring in the original PCB, and then re-layed the copper. The problem is solved, and the specific reason is currently unclear.
In the end, my results are shown in the figure.
I ’m a noob, please forgive me for any errors in the article.