Appendix F — Programming, fuses and bootloaders

Purpose

Understand how firmware reaches the MCU and which configuration choices can affect whether the target remains easily programmable.

ISP

AVR ISP uses the MCU's programming interface plus RESET. EduBoard-AVR keeps this path available even when teaching peripherals are fitted.

AVRDUDE workflow

Identify the exact MCU, programmer and connection before writing. Read/verify identity and existing configuration where practical, program Flash, then verify.

Fuses

Fuses configure device behavior such as clock-related options and other low-level features. Treat fuse changes as configuration changes with recovery consequences, not as ordinary firmware bytes.

Before changing fuses: 1. read the ATmega1284P datasheet section for the exact bits; 2. record existing values; 3. calculate intended values independently; 4. verify clock assumptions; 5. know the recovery path; 6. change only what the lab requires.

Lock bits

Lock bits control programming/read-access policies. They are not a substitute for understanding the device's actual security guarantees.

Boot section

Study reset/boot placement and the architectural idea of a bootloader before using an Arduino-style bootloader. A bootloader is optional; ISP remains the foundational programming path.

Recovery mindset

A configuration that makes ISP appear dead may have changed clock/reset/programming assumptions. Diagnose power, reset, clock and programmer wiring before assuming the MCU is destroyed.

Safety rule

Do not provide copy/paste fuse values without tying them to an exact target, clock design and documented recovery procedure.