Mr. IntegralUNIT 01 · FOUNDATIONS
Signals and Circuits
Where the software meets the wire.
Firmware controls the world through pins, and pins obey physics. When a button reads as pressed twice, an LED is dim, or a chip resets for no reason, the explanation is almost always in this unit. Each lesson starts from a concrete question, builds the idea with a circuit you can adjust, works one example numerically, and ends with questions to check yourself.
The unit in six ideas
- 1Voltage is a difference between two points; ground is the point you chose to call zero.
- 2An input guarantees a 0 at or below and a 1 at or above ; between them it guarantees nothing.
- 3A resistor sets a current () or sets a default level; pull-ups and pull-downs do the second job.
- 4: a capacitor holds charge in proportion to its voltage, and : it passes current only while its voltage changes.
- 5Learn the polarity markers: LED long lead and flat rim, capacitor stripe, diode band. Transistor pinouts come from the datasheet.
- 6A schematic is a diagram of nets. Read power and ground first, then each signal from where it is produced to where it is consumed.
Lessons
Voltage, Current, and Ground
Three point three volts relative to what?
Digital Signals and Logic Levels
Where is the line, who draws it, and what happens to a voltage that lands near it?
Resistors, Pull-Ups, and Pull-Downs
Why a resistor limits current, why an unconnected input has no defined value, and how a pull-up or pull-down gives a button a default state without wasting power.
Capacitors and Decoupling
And why does the layout guide insist it be close, when a wire carries current just as well from ten millimetres away as from one?
Switches, LEDs, and Interface Circuits
Recognising real parts and their symbols, why switch contacts bounce, how to pick an LED resistor from its forward voltage, and how a MOSFET lets a small pin switch a large load safely.
Reading Schematics and Datasheets
How to read a schematic net by net, and how to find the numbers that matter in a datasheet: absolute maximums, operating conditions, min/typ/max limits with their test conditions, and pin functions.