Microcontrollers and processors
Pinouts, beginner projects and how processors work inside. Each page shows the calculation that decides whether a circuit works, such as LED current or ADC step size.
Pages in this section
- Computer architectureHow the ARM1 decoded its instructionsWhat microcode is, how the 1985 ARM1 ran each instruction as 1 to 4 rows of a 42-row decode PLA, and why that table is far smaller than 8086 or 68000 microcode.
- Microcontrollers8051 microcontroller pin diagram and pin descriptionAll 40 pins of the 8051 (AT89S52, AT89C51) DIP, checked against the Microchip datasheet: ports P0 to P3 and alternate functions, RST, ALE, PSEN, EA, crystal.
- Microcontrollers15 Arduino projects for beginners, in the order that teaches the mostFifteen Arduino UNO projects, from a blinking LED to a battery monitor, each with the one calculation that decides if it works: LED current, ADC, PWM, servo.
Lessons behind these pages
- Logic levelsWhat counts as HIGH and LOW on a 5 V and a 3.3 V pin.
- ADC and DAC basicsWhere the 4.9 mV step of a 10-bit, 5 V ADC comes from.
- Duty cycle and PWMHow analogWrite() dims an LED without a real analogue output.
- LED circuitsSeries resistors and current limits for the first projects.
- Steppers and servosThe pulse widths a hobby servo expects.
- Crystals and resonatorsThe clock on XTAL1 and XTAL2 of an 8051.
- Logic familiesTTL and CMOS, and why mixing them needs care.