From Firmware to Product

Shipping a real embedded/IoT device is more than code — you specify the hardware the firmware needs and assemble the right supporting chips around the MCU. This page covers defining hardware requirements and a catalog of the building blocks that show up on almost every board.

Defining hardware requirements

Translate the product's job into concrete specs before choosing the MCU:

Requirement	What to estimate / specify
Flash	Code + assets + OTA (often dual-bank = ~2×) + ~20–30% headroom
RAM	Buffers + RTOS task stacks + network/TLS stack + heap + headroom
Performance	FPU/DSP if heavy math; core class for the workload
Security	Secure boot / key storage → add a secure element
Connectivity	Which buses & radios → pick the right transceivers/modules
Storage	Logs/config/data → external flash or EEPROM
Power	Source, budget, sleep currents, battery life
Environment	Temperature grade, sealing, ESD/surge protection
Bring-up	Debug header (SWD), test points, fiducials

TLS and network stacks are RAM-hungry

A "small" connected feature (Wi-Fi + TLS) can need tens of KB of RAM for buffers and certificates. Budget RAM for the whole stack, not just your application logic.

Common building blocks

What you typically place around the MCU, grouped by function.

Power

• LDO (low-dropout linear regulator) — simple, low-noise, low current. e.g. AMS1117, MCP1700.
• Buck / boost (switching) — efficient, for higher current or big step-downs.
• PMIC / battery charger / fuel gauge — e.g. TP4056 charger for Li-ion products.
• Protection — TVS/ESD diodes, reverse-polarity protection, fuses.

Clocking (crystals & oscillators)

• Main crystal (HSE) — accurate system clock, e.g. 8–25 MHz, needs correct load capacitors.
• 32.768 kHz crystal — for the RTC / low-power timekeeping.
• TCXO / oscillator module — when you need high accuracy (e.g. radio, precise timing).
• Internal RC — convenient but imprecise.

Some peripherals require a real crystal

USB, CAN and precise UART baud rates generally need an external crystal — the internal RC oscillator usually isn't accurate enough. Decide clocking early.

Memory & storage

• SPI / QSPI NOR flash — external code/data/OTA storage. e.g. W25Q series.
• SDRAM / PSRAM — external RAM for large buffers (displays, MPUs, ESP32 PSRAM).
• EEPROM — small non-volatile config. e.g. 24Cxx (I²C).
• eMMC / NAND / SD card — mass storage for logs and filesystems.

Interface & signal-conversion chips

These bridge the MCU's logic-level pins to real-world buses and other voltage/isolation domains:

Function	Common part	What it does
USB ↔ UART bridge	CH340, CP2102, FT232	Program/console over USB
CAN transceiver	TJA1050, SN65HVD230	MCU CAN controller ↔ differential CAN bus
RS-485 transceiver	MAX485, THVD series	Differential, multidrop industrial bus
RS-232 level shifter	MAX232	Legacy serial voltage levels
Digital isolator	ADuM1201 (ADI)	Pass signals across isolated ground/safety domains
Logic level shifter	—	3.3 V ↔ 5 V interfacing
Ethernet PHY	LAN8720 (+ RJ45 magnetics)	MAC ↔ physical Ethernet

Why isolation (e.g. ADuM1201)?

Isolators break ground loops and protect the MCU side from high voltage or noisy domains — essential in industrial, medical and mains-connected designs. Some parts also carry isolated power (e.g. ADuM5xxx family).

Connectivity / radio

• Wi-Fi / BLE — module or SoC (e.g. ESP32).
• Cellular — modem modules (e.g. SIMxx, Quectel) for LTE/NB-IoT.
• LoRa — long-range, low-power (e.g. SX127x).
• GNSS — positioning modules.

Security

• Secure element / crypto-auth IC — e.g. ATECC608, NXP SE050 — protected key storage, authentication, and secure-boot support, kept off the main MCU.

Real-time clock & misc

• RTC chip (e.g. DS3231) + coin cell — keep time while powered off.
• Sensors — IMU, temperature/humidity, etc.
• GPIO/port expanders (I²C) when you run out of pins.

A minimal IoT node — typical BOM shape

• MCU/SoC with Wi-Fi/BLE (e.g. ESP32) · LDO for the rail · crystal + load caps · USB-UART (CH340) for programming · external QSPI flash · sensor(s) · TVS/ESD protection · debug/test points.

Modules vs. discrete

Early on, modules (pre-certified Wi-Fi, cellular, etc.) save design and certification effort. Move to discrete chips only when volume justifies the extra engineering. See PCB cost optimization.

See also: Choosing an MCU · Advanced Topics · PCB Design.