Drawing schematics: what makes a schematic readable

KiCad symbols, net labels, hierarchical sheets. Habits for a schematic that others, and you three months from now, can read.

A schematic is the blueprint of the PCB and the document where firmware developers look up pins. Working is not enough; it has to be readable.

Basic rules

The direction of a readable schematic. Signals run left to right, power top to bottom.

Lay it out so signals flow left to right and power flows top to bottom
Connect with net labels instead of dragging long wires (UART1_TX, MOTOR_PWM_A)
Put direction and ownership in net names: IMU_SCK shows the purpose better than MCU_SPI1_SCK
Put the voltage in power net names: +3V3, +5V, VBAT
Draw decoupling capacitors grouped next to their chip, with values shown

Hierarchical sheets

Split power, MCU, sensors, motor driver and connectors into sheets. Drawn on one page, anything over 50 parts becomes unreadable.

RoadmapSee where this note sits in PCB Design→

Part information

Put the value, package (footprint) and manufacturer part number (MPN) on every symbol and the BOM comes out automatically. Adding rated voltage and power in fields speeds up reviews.

ERC

KiCad's electrical rules check (ERC) finds unconnected pins, outputs tied together and nets with no power source. Getting the warnings to zero before moving on has to become a habit.