General rules for reading schematics and PCB layout

  1. When reading the PCB layout and schematics, for 2-layer PCB, the red layer usually means top layer, and blue or gray layer usually means bottom layer. With PCB with more than 2 layers, the color code will be different.
  2. All layers shown are in the top view perspective.
  3. “Vias” are nodes that connect the 2 top and bottom layers. You can spot a lot of vias in a PCB design, they look like a dead-end (connect to nothing on the current layer), because they actually connect to another layer! As the 2 layers are all top view, we can easily see where the via will connect to. The image below showing you an example of via and how via connects 2 layers together.

Example of via

Example of via

  1. IO pins are different from physical pins. The IO pin as understood by the chip and the source code is different from the physical order of the pin. Always refer to the pin using its IO index, and use the chip datasheet to know where that IO pin is physically. See the attached image, the pin layout of the ESP32 chip shows that the physical pin at physical position 6 is actually IO34.

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  1. Labels of pins are unique, meaning that if you see 2 pins/connections with the same name, it means that they are connected to each other.

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