Public:Schematic Conventions

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Our team is in the process of creating and implementing standards for all of our electrical design and CAD. This is being done in an attempt to reduce errors in manufactured boards, make it easier for other members to edit boards that were already created, and make the finished CAD look presentable. We will also create a project template to set the DRC (Design Rule Checker) to our standards and make all our boards follow Bay Area Circuits' manufacturing constraints.

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All content below this point is under construction

 

General Advice for Clean Schematics

Be consistent with whatever conventions you choose, if we do not require a specific standard!

If you think something is hard to read or confusing, and you are following whatever conventions listed here, please post your dilemma in the #elec-cad channel on ((Slack)).

Net Naming

All nets with more than two pins should be named with a descriptive name.

Net names should only contain capital letters, numbers, and underscores. Net names should never contain spaces.

More guidance on net naming will be provided at a later time

Power Rails

No VCC/VDD. Net names should indicate the polarity and voltage of the rail. If the zero voltage reference of the rail is not the net named "GND", the net name of the power rail must reflect this.

• Voltage Rail should be near the top of the schematic
• *Voltage symbol usually points upwards
• *In the case of a voltage output, e.g. from a DC/DC converter, voltage symbol may point sideways
• GND Rail should be near/at bottom
• *GND symbol always points downwards
• If there is a decimal point in the voltage, use the convention of replacing the decimal with V for voltage, e.g. +3V3 describes +3.3V

I2C/SPI

Will expand on this later

UART

It is very easy to get mixed up with UART nets, be thorough and double check your work!

UARTx_Source_to_Destination

Examples

Put some examples here

Graphical Considerations

Schematics are the most critical piece of documentation for a PCB. They are read by both ECAD software and fellow engineers. The schematic should clearly illustrate its functionality, be easy to read, and contain enough information so that it is easy to order parts and assemble the finished PCB.

More information will be provided at a later time

Wire Crossings

Long answer short, dots on all 3-way intersections, no dots on 4-way intersections. A dot means that the wires connect, no dot means that there's no connection. Just avoid 4-way intersections as much as possible because there are two different conventions that contradict each other. If you think you are going to encounter a 4-way connection, separate it into two 3-way connections instead.

70px In this example, there are two cases where a wire comes in at a perpendicular angle and connects to another. There is also a 4-way intersection, but the two wires that are crossing there are not actually connected to each other. This is the most readable way to arrange these wires in this case. If the wire coming from 2 had to connect to 3, the designer would need to first make a 3-way connection from 2 to 3, and then at a slightly different place on 3's line, make a 3-way connection from 3 to GND, like so:

Direct Wire Connections

Wires should be as straight as possible to make it easier for the eye to follow.

Routing from Components

Route lines should come straight out of components, as opposed to immediately making an angle. This makes it easier to move components later on.

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Prevent Overlapping

Components, reference designators, and part values must never overlap anything. The only thing that wires can cross is other wires. Text comments should not overlap anything.

Net Coloring

While net coloring can be useful to easily identity and follow nets around a schematic, the schematic should be completely intelligible without net coloring. This is because the schematic will most likely be printed in black and white if it is printed.

Paper Size and Title Block

Paper size: ANSI A (8.5" x 11")

We need to be able to print out all of our current schematics at any time as a backup

Diptrace archives may not use any standard paper size, as we did not enforce the standard on our boards when we used it.

Title Block: Kicad Default, Diptrace --TBD-- now defunct, do not use

Include information in these fields:

Part Information

Using just the schematic, anyone should be able to determine which parts should be ordered to assemble the board. To achieve this, the following guidelines should be followed to ensure that all necessary information is included in the schematic.

Still working on this

This is an example for a Schottky diode. The value is the reverse voltage value, one of the most important values for Schottky diodes. The P/N field had to be added to the Fields by clicking the blue + button.

70px

Symbol Creation

Look, please make symbols that aren't shit or look like shit. If you have questions, please refer to the Kicad Library Conventions for now.

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Recommended Reading

Rules and Guidelines for Drawing Good Schematics

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