Technical Resources

Application notes, selection guides, and technical articles

GD32 Low-Power Modes: Choosing Between Run / Sleep / Deep-sleep / Standby

The key to power saving is duty-cycling: the deeper you sleep and the shorter the active time, the longer the battery lasts. This guide covers GD32's four states (Run/Sleep/Deep-sleep/Standby) — what stays on, how it wakes, whether RAM is retained, and the current tier — and states honestly that Standby resets + loses RAM and the µA figures are typical, not guaranteed, then points out the real advantage of the low-power GD32L23x line: µA-level modes that still retain SRAM.

GigaDeviceGD32Low PowerSleep

Published: 2026-06-30

Cold-Chain Temperature RFID: The EM4325 Semi-Passive UHF + Temp Sensor (Passive vs BAP vs Active)

A cold chain must "prove the range was held without opening the box." Temperature RFID splits into passive (reads only when interrogated), semi-passive BAP (battery-driven interval monitoring, like the EM4325), and active. This guide covers the three and the EM4325 (UHF Gen2 + temp sensor + SPI), and states honestly: the EM4325 natively does snapshots + interval alarm monitoring; full point-by-point logging needs a companion MCU.

EM MicroEM4325RFIDUHF

Published: 2026-06-30

RS-485 Wiring & Termination Design: Termination, Fail-Safe Biasing, Daisy-Chain and Stubs

RS-485 instability is 90% wiring: termination not at both ends, star topology, no bias on the idle bus. This guide covers the three rules — termination = cable impedance (120Ω is typical, not mandated), a linear daisy-chain, and fail-safe biasing — plus stub/grounding/node-count/rate-length engineering rules. RS-485 is the Modbus RTU physical layer, funneling to W5500/DM9051 RTU→TCP gateways.

RS-485ModbusTerminationFail-Safe

Published: 2026-06-30

Low-Cost Entry MCU: Selecting the FMD FT61F 8-bit (FT61F02X vs FT61F14X)

The FMD FT61F is an 8-bit RISC general-purpose MCU (not Arm, not a touch MCU), for cost-sensitive access-control/lighting/instrument/small-appliance control. It splits into the entry FT61F02X (10-bit ADC, 6 timers, no UART) and the higher FT61F14X (12-bit ADC, USART, 1.9V). This guide covers choosing between the two sub-families, when to step up to Arm, and FMD's one-stop (MCU+EEPROM+power) advantage.

FMDFT61F8-bit MCUMCU

Published: 2026-06-30

Choosing GD32 USB: Device/Host/OTG, FS vs HS, and Built-in HS PHY vs External ULPI

Picking a GD32 for USB starts with three questions: device/host/OTG? Is FS (12Mbps) enough or do you need HS (480Mbps)? If HS, is the PHY built in or do you bolt on a ULPI? The key trap: the GD32F4xx USB-HS REQUIRES an external ULPI PHY; only the GD32H7 has a built-in HS PHY. This guide lays out USB across the GD32 families (F103/F303 device-only, F305/F307 OTG, F4xx, H7).

GigaDeviceUSBGD32USB-HS

Published: 2026-06-28

QSPI (Quad-SPI) NOR Flash and XIP: How to Wire It and Run Memory-Mapped Code

Quad-SPI uses 4 data lines and 2 clocks per byte, ~4× the throughput of standard SPI; XIP lets the CPU execute code in place from external flash without copying to RAM first. But XIP requires NOR (random read) — NAND can't. This guide covers SPI/Dual/Quad, how XIP works, and maps to GD25Q plus "the MCU side needs a QSPI/OSPI controller (only some GD32 have one)."

GigaDeviceQSPINOR FlashXIP

Published: 2026-06-28

Energy-Harvesting PMIC: Battery-less / Ultra-Low-Power IoT with the EM Micro EM8500

Energy harvesting frees sensors from battery swaps: ambient energy (solar/thermal) → an energy-harvesting PMIC → storage → an ultra-low-power load, at µW–mW scale. This guide covers how to select an energy-harvesting PMIC (cold-start, MPPT, storage, rails, Iq), using the EM Micro EM8500 (0.3V cold-start, HW MPPT, dual storage, 4 rails, 125nA) as the worked example, paired with the EM6819 MCU.

EM MicroEM8500Energy HarvestingPMIC

Published: 2026-06-28

Schottky Diode Selection: Vf, Leakage, and Si vs SiC (Low-Voltage Rectification to 650V SiC)

A Schottky diode has low forward drop, fast switching and near-zero reverse recovery — ideal for high-frequency rectification and freewheeling; the costs are high leakage and (for silicon) a low reverse-voltage ceiling (~≤100–200V). Above that you need SiC (650V/1200V). This guide covers the selection params and Si-vs-SiC, and maps to Huixin, which supplies both silicon Schottky (SB160) and SiC Schottky (HSC04065AC, 650V/4A class).

HuixinSchottkySiCDiode

Published: 2026-06-28

RS-232 vs RS-485 vs CAN: Choosing an Industrial Serial Bus (Physical vs Protocol Layer Is the Key)

RS-232/RS-485/CAN aren’t three competing protocols but two layers: RS-232 (single-ended point-to-point) and RS-485 (differential multi-drop) are physical-layer only, needing a protocol (e.g. Modbus RTU) on top; CAN builds in the data-link layer (framing/arbitration/error handling). This guide explains that key difference and maps to GD32 CAN-FD (G5/H7/F5) and classical CAN (L235).

RS-232RS-485CANCAN-FD

Published: 2026-06-28

I²C vs SPI vs UART: Choosing an Embedded Serial Interface (Wires, Addressing, Speed)

Which serial interface for connecting peripherals to an MCU? Three axes decide: wire count, how many devices share the line (addressing vs one CS each), and speed. UART is two devices point-to-point (async, no clock); I²C is a row of addressable low-speed devices on two wires (needs pull-ups); SPI trades one CS per device for high speed. This guide breaks each down and maps to FMD FT24C, GigaDevice GD25Q and WIZnet WizFi360.

I2CSPIUARTSerial

Published: 2026-06-28

EEPROM vs NOR Flash vs FRAM: Choosing Non-Volatile Memory by the Job, Not the Buzzword

Choosing non-volatile memory wrong isn’t about “can it work” — it’s being too expensive, too slow, or worn out. Using four axes (erase granularity, read access, write endurance, density/cost), this guide explains EEPROM (byte-write, for settings), NOR Flash (XIP, for code), NAND (bulk), and FRAM (near-unlimited endurance but small and pricey), mapped to FMD FT24C and GigaDevice GD25Q / GD5F.

FMDGigaDeviceEEPROMNOR Flash

Published: 2026-06-28

Calculating and Choosing a 32.768kHz Crystal’s Load Capacitance (CL): Get It Wrong and Your RTC Drifts

Keeping a 32.768kHz crystal accurate comes down to matching the load capacitance (CL): the wrong CL pulls the frequency and becomes RTC timekeeping error. This guide covers the CL formula (C1=C2≈2×(CL−C_stray)), the two pitfalls of a 32.768kHz tuning-fork crystal (pulling sensitivity and over-drive), and compares a bare crystal (Micro Crystal CM8V-T1A) with cap-free integrated RTC modules (the RV series).

Micro CrystalCrystalLoad Capacitance32.768kHz

Published: 2026-06-28

Why FOC Motor Control Wants the Cortex-M4’s DSP+FPU: Selecting a GD32 Motor MCU

An FOC current loop must finish the Clarke/Park/PI/SVPWM chain of floating-point and trig within each PWM period, with the loop running at 10–20kHz. An M0/M3 without an FPU emulates floats in software — slow and jittery; the Cortex-M4’s hardware FPU+DSP buys speed and determinism. This guide explains why and maps it to the GD32F30x / GD32F4xx with their FPU+DSP, advanced PWM timer and PWM-synchronized ADC.

GigaDeviceFOCMotor ControlCortex-M4

Published: 2026-06-28

Modbus RTU vs Modbus TCP, and Building an RTU→TCP Gateway with the W5500 / DM9051

Modbus RTU and TCP are really two transport layers of the same protocol: identical data model and function codes, differing only in physical layer, framing and checksum (RTU uses CRC-16 over serial; TCP uses an MBAP header on port 502 with no CRC). This guide explains the difference and how to build an RTU→TCP gateway with the hardwired-TCP/IP W5500 (least effort) or the SPI MAC+PHY DM9051 (most flexible).

WIZnetDAVICOMModbusRS-485

Published: 2026-06-28

13.56MHz HF RFID (ISO 14443 / 15693) and How It Relates to NFC: Choosing the EM4233

“All 13.56MHz tags are NFC” is a misconception. 13.56MHz is the HF band, holding two standards — ISO 14443 (proximity: payment/access) and ISO 15693 (vicinity: asset/library); NFC is a device-side layer where NFC-A/B map to 14443 and NFC-V/Type 5 maps to 15693. This guide clears up the hierarchy and shows how to choose between the EM4233 (ISO 15693) and the dual-frequency EM4425/EM4423 (ISO 14443 + UHF).

EM MicroRFIDNFCISO 15693

Published: 2026-06-28

Choosing an LPWAN: LoRaWAN vs NB-IoT vs Sigfox (First Decide If You Want Your Own Network)

The first LPWAN question isn’t “which has the longest range” but “do you want to own the network”: LoRaWAN is unlicensed, you can run your own gateway with no carrier fee; NB-IoT is licensed, carrier-operated, strong deep-indoor; Sigfox is ultra-low-rate but carries operator risk. This guide compares all three and maps them to KIWI Technology’s LoRaWAN gateways.

KIWILoRaWANNB-IoTSigfox

Published: 2026-06-28

Choosing an Arm Cortex-M Core: M0+/M23/M3/M4/M33 Differences and the Matching GD32 Family

Cortex-M0+/M3/M4/M33 sound alike; the differences come down to four axes: FPU, DSP, TrustZone and power. This guide explains the core features first, then maps them to GigaDevice’s GD32 families (including the common trap that the GD32C103 is actually an M4, not an M3), so three yes/no questions get you to the right MCU.

GigaDeviceCortex-MGD32MCU

Published: 2026-06-28

Upgrading a Legacy WIZnet W5100 Design: W5100S or W5500? (Compatibility at a Glance)

Maintaining a legacy W5100 design, facing EOL risk or wanting lower power? WIZnet offers two upgrade paths: W5100→W5100S (firmware unchanged, adds power-saving and WoL, but the package goes 80→48 pin so the board is re-laid-out) and W5100→W5500 (8 sockets/32KB/80MHz). This guide lays out the trade-offs in one compatibility table.

WIZnetW5100W5100SW5500

Published: 2026-06-28

USB-to-Ethernet Controllers: DAVICOM DM9601 vs DM9621 (USB 1.1 vs USB 2.0 Is the Key)

A USB-to-Ethernet controller turns a host that has a USB port but no Ethernet MAC into a standard NIC via a driver. The DM9601 and DM9621 are both 10/100 on the Ethernet side; the difference is USB — DM9601 is USB 1.1 (12Mbps, can’t fill 100Mbps) while DM9621 is USB 2.0 (480Mbps). This guide shows how to choose and contrasts SPI (DM9051) and MAC+PHY approaches.

DAVICOMUSBEthernetDM9601

Published: 2026-06-28

Four Ways to Add Ethernet: Hardwired TCP/IP vs MCU MAC+PHY vs SPI MAC+PHY

There are four architectures for adding Ethernet to a product, differing in where the TCP/IP stack runs, whether the MCU has a MAC, and what interface is used. This guide lays out hardwired TCP/IP (WIZnet W5500), MCU MAC + external PHY (GD32 + DAVICOM), SPI MAC+PHY (DM9051) and the software-stack option, with a three-question decision table.

WIZnetDAVICOMGigaDeviceEthernet

Published: 2026-06-28

DS3231 / DS1307 RTC Shortage? Replacing with Micro Crystal RV Series (Heads-up: Firmware Must Change)

Facing cost and lead-time pressure on the DS3231 / DS1307, the Micro Crystal RV series is a functional alternative — but not a drop-in: the DS parts use I²C address 0x68, while RV-8803/RV-3028/RV-8564 use 0x32/0x52/0x51 with different register maps, so a swap requires firmware changes. This guide sorts the choice by whether you need temperature compensation and makes the migration cost clear.

Micro CrystalRTCDS3231DS1307

Published: 2026-06-27

AT24C / 24Cxx EEPROM Shortage or Cost-Down? Second-Sourcing with FMD FT24C (Mind the Page Size)

The 24Cxx I²C EEPROM is a multi-vendor de-facto standard, and FMD (Fremont Micro Devices) FT24C is a pin- and protocol-compatible same-density second source (1K–1Mbit, 1.8–5.5V). But check the page size before swapping — at 1K/2K density FMD uses a 16-byte page while Atmel AT24C01/02 uses 8 bytes, and getting it wrong overwrites data. Here is how to migrate safely.

FMDEEPROM24CxxAT24C

Published: 2026-06-27

CAN vs CAN-FD and MCU Selection: Which GD32 Parts Actually Integrate CAN-FD

CAN-FD grows the per-frame payload from 8 to 64 bytes and speeds up the data phase, but it does not transparently coexist with classical CAN. This guide clarifies the differences and compatibility reality, verifies per-part which GD32 actually integrate CAN-FD (GD32G5/H7/F5 do; GD32L235 is classical CAN only), and shows how to pick by core and CAN-FD channel count.

GigaDeviceCANCAN-FDGD32G553

Published: 2026-06-27

Industrial vs Commercial vs Automotive: Reading Component Temperature & Quality Grades (AEC-Q100 / Q200)

“−40~+125°C” is not the same as “automotive grade.” The temperature range is a datasheet spec with no single legal standard; AEC-Q is a qualification — a battery of reliability tests. This guide clarifies the commercial/industrial/military temperature conventions and the AEC-Q100 (ICs) and AEC-Q200 (passives, incl. crystals) grades, so you check both axes when sourcing.

AEC-Q100AEC-Q200IndustrialAutomotive

Published: 2026-06-27

Choosing RTC Timekeeping Accuracy: Plain Crystal vs TCXO / DTCXO (ppm, Drift & Seconds per Month)

Same 32.768kHz, yet accuracy can differ tens-fold over temperature. This guide converts ppm into seconds-per-month, explains the tuning-fork parabolic drift, and uses Micro Crystal’s CM8V-T1A (bare crystal), RV-3028-C7 (room-temp-accurate RTC) and RV-8803-C7 (DTCXO temperature-compensated RTC) as three tiers to pick by your accuracy need.

Micro CrystalRTCDTCXOTCXO

Published: 2026-06-27

UHF RFID Is Not “Active”: Passive vs Battery-Assisted Passive (BAP) vs Active, and How to Choose

Mainstream UHF RFID (RAIN, 860–960MHz, EPC Gen2) is overwhelmingly passive, with a battery-assisted passive (BAP) tier for sensing; true active RFID lives at 433MHz/2.45GHz as a separate system. This guide clarifies the three power architectures, maps them to EM Micro’s EM4124/EM4126 (passive) and EM4325 (BAP), and shows how to choose.

EM MicroelectronicsUHF RFIDRAIN RFIDEPC Gen2

Published: 2026-06-27

PoE Standards 802.3af / at / bt and Powered-Device (PD) Design: How Many Watts Do You Actually Get?

The three PoE standards (802.3af / at / bt) deliver very different power — and the PD never receives as much as the PSE rating. This guide clarifies the af/at/bt power and cabling differences, the powering handshake, the PD-side power front-end, and uses the WIZnet WIZPoE-P1 module as the fast PD solution.

WIZnetPoEPoE+802.3af

Published: 2026-06-27

STM32 Alternatives with GigaDevice GD32: Cost-Down & Supply Security (Pin-to-Pin Map + Migration Pitfalls)

Facing STM32 cost pressure, a specific part going EOL, or the need for a second source? GigaDevice GD32 is a domestic alternative closely aligned in pinout and peripherals. Here is the GD32↔STM32 map, the truth about compatibility, and the pitfalls that bite during migration (including the classic “GD32F303 is not an STM32F303” trap).

GigaDeviceSTM32GD32Cross-Reference

Published: 2026-06-27

125kHz RFID Access-Control Reader Design: EM4100 / EM4200 Tags and the EM4095 Reader AFE

A 125kHz access-control system is built from read-only tags (EM4100/EM4200), a reader analog front-end (EM4095) and an MCU that decodes. This guide explains how the system works, the difference between EM4100 and EM4200, what the EM4095 does, and when to step up to the read/write EM4305.

EM Microelectronics125kHz RFIDEM4100EM4200

Published: 2026-06-24

Ethernet PHY Selection: RMII vs MII, and What to Watch When Replacing LAN8720A with DAVICOM DM9162

How do you choose between RMII and MII? The key is the clock. DM9162 and LAN8720A are both RMII 10/100 PHYs sharing the clause-22 MDIO interface, so they are functional second sources — but packages, straps and firmware PHY-init differ, making it an alternative that needs a layout and firmware review, not a blind drop-in.

DAVICOMEthernet PHYRMIIMII

Published: 2026-06-24

Low-Cost Industrial Ethernet with GD32’s Integrated MAC + a DAVICOM PHY (GD32F207 / F407 + DM9161A / DM9162)

GD32F207 / GD32F407 integrate a 10/100 Ethernet MAC; add a DAVICOM DM9161A / DM9162 PHY over MII or RMII to build low-cost industrial Ethernet. This guide clarifies which GD32 parts actually have the MAC, how the MAC connects to a PHY, and the real difference between DM9161A and DM9162.

GigaDeviceDAVICOMGD32F207GD32F407

Published: 2026-06-24

Choosing SPI NAND Flash: How It Differs from SPI NOR, with GigaDevice GD5F1GQ5 / GD5F2GQ5

SPI NAND reads by page, erases by block and needs ECC and bad-block management — in exchange for far higher density and lower cost-per-bit than SPI NOR. Using GD5F1GQ5 (1Gb) and GD5F2GQ5 (2Gb), learn when to move from NOR to NAND and how to second-source.

GigaDeviceSPI NANDSPI NORGD5F1GQ5

Published: 2026-06-24

Flyback Controller Selection: Quasi-Resonant (QR) vs Fixed-Frequency PWM — On-Bright OB2201 / OB2358 / OB2500

How to pick a flyback IC: QR vs fixed-frequency PWM, external-MOSFET controller vs integrated-MOSFET power switch, and PSR vs SSR — using On-Bright OB2201, OB2358 and OB2500 as worked examples.

On-BrightFlybackQuasi-ResonantQR

Published: 2026-06-24

What Is Hardwired TCP/IP? How WIZnet W5500 / W6100 / W6300 Offload Your MCU

Hardwired TCP/IP puts the whole protocol stack in silicon — the MCU just reads and writes socket registers over SPI/QSPI. Compare W5500 (IPv4), W6100 (IPv4/IPv6 dual stack) and W6300 (IPv6 + QSPI throughput) to pick the right part.

WIZnetHardwired TCP/IPW5500W6100

Published: 2026-06-24

GD25Q as a W25Q Replacement: SPI NOR Flash Second-Source Guide

When Winbond W25Q is short or you want to diversify supply, GigaDevice's GD25Q is a common pin-compatible second source. This guide covers JEDEC pinout and command compatibility, the QE bit, migration tips, and density mapping.

GD25QW25QSPI NOR FlashCross-Reference

Published: 2026-06-02

Replacing STM32F103 with GD32F103: Compatibility, Migration & Sourcing

When STM32F103 is in shortage or on long lead times, GigaDevice's GD32F103 is a common pin-compatible second source. This guide covers pinout and register compatibility, the 108MHz vs 72MHz difference, migration tips, and how to source it.

GD32F103STM32F103Cross-ReferenceCross-Reference

Published: 2026-05-30

Ultra-Low-Power RTC Selection: RV-3028-C7 vs DS3231 vs PCF8563

For battery devices, an RTC's timekeeping current drives battery life. This article compares Micro Crystal's RV-3028-C7, the DS3231, and the PCF8563 on power, accuracy, and best-fit use, to help you pick the right real-time clock.

RTCRV-3028-C7DS3231PCF8563

Published: 2026-05-26

Choosing an SPI Ethernet Chip: W5500 vs ENC28J60 vs DM9051

When adding wired networking to an MCU, the W5500, ENC28J60, and DM9051 are three common SPI options. This article compares hardwired TCP/IP versus a software stack, their specs and best-fit scenarios, plus shortage alternatives and sourcing.

W5500ENC28J60DM9051SPI Ethernet

Published: 2026-05-18

WizFi360 as an ESP8266 Replacement: a Footprint-Compatible Wi-Fi Module

Need a second source or industrial-grade alternative to the ESP8266/ESP-12F? The WIZnet WizFi360 is footprint-compatible with an AT-command interface. This article covers compatibility, migration tips, and sourcing.

WizFi360ESP8266Wi-Fi ModuleCross-Reference

Published: 2026-05-10

LM2596 Buck Regulator: Selection, LM2576 Comparison & Second Source

The LM2596 is one of the industry's most common 3A buck regulators. This article covers how it is used, how it differs from the LM2576, and how a pin-compatible TAEJIN second source can de-risk supply.

LM2596LM2576Buck RegulatorBuck Converter

Published: 2026-04-28

I²C EEPROM Selection: 24Cxx Densities, Wiring & FT24C Replacement

The 24Cxx family of I²C EEPROMs is the most common small non-volatile memory. This article covers density naming, wiring and addressing, and how FMD's FT24C series replaces AT24C / 24LC / M24C parts.

EEPROM24C0224C256I2C

Published: 2026-04-12

Choosing a LoRaWAN Gateway: Single-Channel, All-in-One, and 16-Channel Industrial

A LoRaWAN gateway bridges LoRa end-nodes and the network server, and channel count sets capacity. This article explains how to choose by deployment size, indoor/industrial environment, and network-server needs, mapped to KIWI's three gateways.

LoRaWANGatewayLoRaIoT

Published: 2026-03-22

Dual-Frequency RFID: EM4425 / EM4423 Combining NFC and UHF

One chip supporting both NFC (a phone tap) and UHF (long-range bulk inventory). This article explains the value of dual-frequency RFID, the difference between the EM4425 and EM4423, and where they fit.

RFIDNFCUHFEM4425

Published: 2026-03-08

Choosing Across the GD32 MCU Family: STM32 Alignment and Use Cases

GigaDevice's GD32 family spans Cortex-M3, M4, M23, and RISC-V, largely positioned to align with STM32. This article maps each family's core, positioning, and best-fit use to help you select quickly.

GD32MCUCortex-MSTM32

Published: 2026-02-22

Selecting On-Bright AC/DC Power ICs: PWM Controllers, LED Drivers & Fast Charge

On-Bright focuses on offline (AC/DC) power ICs. This article explains the roles of PWM controllers, LED drivers, and USB-PD fast-charge controllers, mapped to the OB2263, OB3350, and OB2632Q.

On-BrightPWMAC/DCLED Driver

Published: 2026-02-06

DAVICOM DM9051 on Embedded Linux: Driver Setup & Debugging

Add Ethernet to a SoC without a built-in MAC using the SPI-interface DM9051: enabling the kernel driver, the device tree node, and common troubleshooting.

DAVICOMDM9051LinuxEmbedded

Published: 2025-04-01

PoE Powered Device Design: Drawing Power from the LAN with WIZPoE-P1

Understand the IEEE 802.3af/at PoE standard and use the WIZPoE-P1 module to design a powered device (PD) that draws power from the Ethernet cable — no separate power wiring.

WIZnetPoEWIZPoE-P1IEEE 802.3af

Published: 2025-03-05

EM6819 Ultra-Low Power Design Tips: Pushing Standby Current to nA

Understand the EM6819 power modes and use voltage, clock, and peripheral management to push standby current into the nA range and maximize coin-cell battery life.

EM MicroelectronicsEM6819Ultra-Low PowerMCU

Published: 2025-02-10

WIZnet W5500 Getting Started: SPI Wiring & Socket Initialization

From the hardwired TCP/IP concept and SPI wiring to ioLibrary initialization and opening your first socket — a step-by-step guide to getting W5500 online with Arduino / STM32.

WIZnetW5500TCP/IPSPI

Published: 2025-01-15