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When creating a PCB symbol for schematics, what is the best practice when creating a symbol: Do you include every pin of the MCU for completeness? For example - TMS570LC4357 uses a NFBGA(ZWT) 337 pin package, should I go through all of section 4 (Terminal Configuration and Functions) in the datasheet and create a pin for each of 337 pins even if I am not using most of them?

Datasheet link: https://www.ti.com/lit/ds/symlink/tms570lc4357.pdf?ts=1673888719937&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTMS570LC4357

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  • \$\begingroup\$ You don't have to, but there might be different opinions what you should do, so there is no exact answer to that. \$\endgroup\$
    – Justme
    Jan 17, 2023 at 13:01
  • \$\begingroup\$ Letting MCU pins float means that you should take care that non are left in a default state of digital input...a pin ignored is one that can turn and bite you. \$\endgroup\$
    – glen_geek
    Jan 17, 2023 at 13:53

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The best practice is to include all the pins. But, do you have to? No, you can be sloppy and only include the ones you are using. But you'll regret it later, when you want to use that same microcontroller for a different project.

Regardless, you don't have to do either: these days you can find ready-made footprints for all microcontrollers.

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Yes, the best way is to draw a schematic symbol which has all the pin of the physical component. This is also for reference with the footprint, that will have ALL the pins in order to produce correct gerber files. Eventually, if you don't want to draw it by yourself you can check if there are symbols and footprints already made and import it. For example on the manufacturer site (CAD Model), or on online libraries as ultralibrarian or also snapeda you should find that symbol and footprint... Please note that the majority of CAD software have built-in function for generating the symbol and footprint automatically, based on number of pins, pitch, dimensions and csv file with pins information.

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