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com:eth_and_micro [2026/07/27 21:46] – created vamsancom:eth_and_micro [2026/07/27 23:01] (current) – vamsan
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 ====== Ethernet and microcontrollers ====== ====== Ethernet and microcontrollers ======
 +A physical Ethernet connection serves as a dedicated hardware link that directly connects local microcontrollers to LANs and industrial fieldbuses. Unlike wireless solutions, a wired Ethernet port ensures reliable, low-latency, and secure communication, which is vital for real-time operations. When combined with internal or external //Media Access Control// (**MAC**) layers and a //Physical Layer// (**PHY**) transceiver, microcontrollers can efficiently process raw network packets, execute Modbus TCP functions, or stream data to central SCADA systems without experiencing signal loss.
  
 +**The MAC (Media Access Control) – The Data Brain**
 +
 +The MAC operates at **Layer 2 (Data Link)** of the OSI model. It acts as the logic controller that packages data into standardized network frames.
 +
 +  * **Core Duties:** Appends or reads destination and source MAC addresses, calculates error-checking checksums (CRC), and enforces network access rules to prevent packet collisions.
 +  * **Implementation:** It is entirely digital. In advanced microcontrollers (like an ESP32 or STM32), the MAC is a dedicated hardware block built right inside the main chip. 
 +
 +**The PHY (Physical Layer Transceiver) – The Electrical Muscle**
 +
 +The PHY operates at **Layer 1 (Physical)** of the OSI model. It acts as the hardware translator that turns digital logic into raw physics.
 +
 +  * **Core Duties:** Translates the digital 1s and 0s from the MAC into differential voltage signals (or pulses) that travel down the physical copper twisted-pair Ethernet cable. It also handles auto-negotiation for line speed (10 vs. 100 Mbps).
 +  * **Implementation:** It is an analog-digital hybrid circuit. Because it deals with physical line voltages, it is almost always housed in an external chip (like the LAN8720) or integrated into a combined chip layout adjacent to the isolation transformer (MagJack).
 +
 +**How They Talk: MII and RMII**
 +
 +The MAC and the PHY must communicate through a highly synchronised digital bus on your PCB. The most common standard is RMII (Reduced Media Independent Interface), which requires a shared, ultra-stable 50 MHz clock signal to precisely sync the transmission and reception lines between the two layers.
 +
 +==== Comparison of some popular Ethernet solutions ====
 +^ Criteria ^ W5100 ^ W5500 ^ W6100 ^ CH9120 ^ ENC28J60 ^ LAN8720 ^
 +^ Price-Level | **Medium** (Becoming obsolete, making modules slightly pricier than W5500) | **Medium-Low** (Mass-produced, highly cost-effective for performance) | **Medium** (Slightly higher premium due to advanced IPv6 features) | **Low** (Extremely cheap integrated chip and minimal component count) | **Very Low** (The cheapest option on the market, but hidden costs in MCU RAM) | **Low** (Very inexpensive chip, but requires a premium MCU to operate) |
 +^ Advantage | * Hardware TCP/IP offloads MCU\\ * Massive community libraries\\ * Industry-proven stability | * Fast SPI clock (80MHz)\\ * Low power consumption\\ * 8 independent sockets | * Native IPv4 and IPv6 support\\ * Pin-compatible upgrade for W5500\\ * 8 sockets | * Extremely easy to use\\ * Requires no TCP/IP stack library\\ * Pure serial-to-ethernet bridge | * Very low cost\\ * Small footprint\\ * Widely available in cheap modules | * True high-speed throughput\\ * Low latency\\ * Uses MCU's native MAC hardware |
 +^ Disadvantage | * Old technology\\ * High power consumption / runs warm\\ * Low socket count (4) | * Limited to IPv4 only\\ * Requires external library (Wiznet) | * Slightly higher cost\\ * Libraries are newer and less mature than W5500 | * Not flexible for complex protocols\\ * Limited to only 2 concurrent sockets | * No hardware TCP/IP stack\\ * Consumes massive MCU RAM and Flash\\ * Slow SPI limits speed | * No MAC layer inside\\ * Requires complex RMII wiring (10+ pins)\\ * Only works with advanced MCUs |
 +^ Supported MCUs | * All 8-bit to 32-bit MCUs\\ * Arduino Uno/Mega\\ * STM32, ESP32, RP2040 | * All 8-bit to 32-bit MCUs\\ * Arduino, ESP32, ESP8266\\ * STM32, RP2040/RP2350 | * Modern 8-bit to 32-bit MCUs\\ * STM32, ESP32, RP2040\\ * Arduino (with updated library) | * Any MCU with a basic UART port\\ * Arduino, PIC, MSP430\\ * Attiny, STM32, ESP32 | * Primarily 8-bit/32-bit MCUs with large RAM\\ * Arduino, STM32, AVR | * Premium MCUs with built-in MAC\\ * ESP32, STM32F4/F7/H7\\ * NXP i.MX, TI Tiva C |
 +^ Technical Parameters | * Speed: 10/100 Mbps\\ * Sockets: 4\\ * Buffer: 16 KB Tx/Rx\\ * Voltage: 3.3V (5V tolerant IO) | * Speed: 10/100 Mbps\\ * Sockets: 8\\ * Buffer: 32 KB Tx/Rx\\ * Voltage: 3.3V (5V tolerant IO) | * Speed: 10/100 Mbps\\ * Sockets: 8\\ * Buffer: 32 KB Tx/Rx\\ * Voltage: 3.3V | * Speed: 10/100 Mbps\\ * Sockets: 2\\ * Buffer: Internal (Fixed configuration)\\ * Voltage: 3.3V - 5V | * Speed: 10 Mbps only (No Fast Eth)\\ * Sockets: Managed by software\\ * Buffer: 8 KB Tx/Rx\\ * Voltage: 3.3V | * Speed: 10/100 Mbps\\ * Sockets: Managed by software/OS\\ * Buffer: Managed by MCU DMA\\ * Voltage: 1.6V to 3.6V |
 +^ Communication Bus | * SPI\\ * Parallel Bus | * High-Speed SPI (Up to 80 MHz) | * High-Speed SPI | * UART (Serial) via AT Commands / Config Tool | * SPI (Up to 20 MHz) | * RMII (Reduced Media Independent Interface) |
 +^ Simatic Modbus TCP | * **Yes** (Via Arduino/MCU Modbus client/server software library) | * **Yes** (Excellent choice; responsive and stable via MCU Modbus libraries) | * **Yes** (Supports Modbus TCP over both IPv4 and IPv6 networks) | * **Limited** (Only via transparent serial bridge; requires specialized Simatic gateway settings) | * **Poor** (Possible, but software TCP/IP stack often drops Modbus packets under load) | * **Excellent** (Native speed, perfect for industrial PLC interfacing via lwIP stack) |
 +
 +==== What is the difference between on-board and external solutions? ====
 +^ Criteria ^ On-board Ethernet (Native MAC + External PHY) ^ External Ethernet Solutions (SPI/UART Controllers) ^
 +^ Description | The microcontroller has a built-in Ethernet MAC core. It connects directly to a physical layer transceiver chip (PHY like LAN8720) via RMII/MII interfaces. | The Ethernet MAC, PHY, and often the TCP/IP stack are integrated into a single external chip (like W5500). It connects to any standard MCU via SPI or UART. |
 +^ Advantage | * **Maximum Speed:** Offers full 10/100 Mbps or Gigabit line rates without bus bottlenecks.\\ * **Low Latency:** Direct memory access (DMA) bypasses serial buses.\\ * **Highly Flexible:** Complete software control over raw packets, custom protocols, and advanced routing. | * **Saves MCU Resources:** Hardware offloads the complete TCP/IP stack; uses near-zero MCU RAM and Flash.\\ * **Universal Compatibility:** Works with any basic MCU possessing a standard SPI or UART port.\\ * **Simpler Hardware Design:** Requires significantly fewer PCB traces and pins (4-6 pins vs 10+ pins). |
 +^ Disadvantage | * **High MCU Resource Consumption:** The software network stack (e.g., lwIP) consumes substantial MCU RAM and Flash.\\ * **Complex PCB Routing:** Requires high-frequency 50MHz trace matching and strict noise isolation guidelines.\\ * **High Pin Count:** Consumes 10 to 12 GPIO pins for the RMII interface. | * **Bandwidth Bottleneck:** Maximum throughput is limited by the SPI or UART bus clock speed.\\ * **Limited Concurrent Connections:** Restricted to a fixed number of hardware sockets (e.g., 8 sockets for W5500, 2 for CH9120).\\ * **No Raw Packet Control:** Harder to implement specialized or non-standard network protocols. |
 +^ Typical Components | * ESP32, STM32F4/F7/H7, NXP i.MX\\ * Paired with PHY chips: **LAN8720, RTL8201, DP83848** | * Any MCU (Arduino Uno, Attiny, RP2040, PIC)\\ * Paired with: **W5500, W6100, W5100, CH9120, ENC28J60** |
 +^ Ideal Use Cases | * Industrial gateways with heavy traffic.\\ * Video streaming or high-frequency data logging.\\ * Systems running a Real-Time OS (RTOS) or Linux with advanced security (TLS/SSL). | * Simple IoT sensors, MQTT clients, and Modbus TCP nodes.\\ * Projects using small, low-cost microcontrollers with limited RAM.\\ * Rapid prototyping and simple PCB layouts. |
 +
 +==== Comparison of some microcontrollers with on-board Ethernet ====
 +^ Product Setup ^ Solution Type ^ Controller / PHY Used ^ Price-Level (Approx.) ^ Main Use Cases ^ Effectivity & Network Performance ^
 +| **Waveshare RP2040-ETH**\\ (Raspberry Nano Ethernet style) | **External**\\ (Integrated Chip) | WCH CH9120\\ (UART-to-Ethernet Bridge) | **Low**\\ (~€11 - €15) | * Simple headless serial data streaming\\ * Remote Modbus-RTU to Modbus-TCP bridges\\ * Compact IoT telemetry devices | **Medium-Low:** Extremely lightweight on MCU resources, but bandwidth is capped by internal UART speeds. Not suitable for complex web hosting or heavy network loads. |
 +| **Arduino Uno R3 / R4**\\ + Arduino Ethernet Shield 2 | **External**\\ (Stackable Shield) | WIZnet W5500 | **Medium**\\ (~€35 - €45 total) | * Learning & academic prototypes\\ * Home automation switches\\ * Small local web servers for status toggles | **Medium:** Excellent hardware offloading (TCP/IP is handled by the shield). However, an 8-bit Uno R3 can struggle with large data buffers despite the chip's speed. |
 +| **Arduino Nano**\\ + Nano Ethernet Shield v1.0 | **External**\\ (Mini Shield Base) | Microchip ENC28J60 | **Very Low**\\ (~€8 - €12 total) | * Lowest-cost custom sensors\\ * Simple ping utilities\\ * Tiny local network triggers | **Low:** The shield lacks a hardware TCP/IP stack, meaning the software network stack must run directly on the Nano's tiny 2KB RAM. Highly prone to crashes under moderate network loads. |
 +| **Arduino MKR Series**\\ + Arduino MKR ETH Shield | **External**\\ (Industrial Form Factor) | WIZnet W5500 | **High**\\ (~€55 - €70 total) | * Industrial IoT edge gateways\\ * Smart building sensors\\ * Professional-grade PLC Modbus TCP nodes | **High:** Blends a high-performance, 32-bit Cortex-M0+ processor with the W5500's stable hardware TCP/IP stack. Ideal for zero-packet-drop industrial applications. |
 +| **ESP32 DevKitC**\\ + LAN8720 Module | **On-board**\\ (Native MAC + Ext. PHY) | Native ESP32 EMAC\\ + LAN8720 PHY | **Low**\\ (~€8 - €12 total) | * High-speed Wi-Fi to Ethernet bridging\\ * Real-time data logging / WebSocket servers\\ * TLS/SSL secured internet appliances | **Very High:** Native DMA access completely eliminates serial bus bottlenecks, pushing real line speeds past 30+ Mbps. Requires software stack memory management (lwIP). |
 +| **STM32F407VET6 Black Board**\\ (with native RJ45 port onboard) | **On-board**\\ (Native MAC + Integrated PHY) | Native STM32 MAC\\ + LAN8720 (or DP83848) | **Medium-Low**\\ (~€15 - €25) | * Industrial control machinery\\ * Heavy-traffic Modbus gateways to SCADA systems\\ * Multithreaded RTOS network routing | **Maximum:** Enterprise-grade performance. High processing power and dedicated memory buses allow raw, sub-millisecond packet control without saturating the processor. |
 +
 +===== Ethernet topics on lamaPLC =====
 +{{topic>Ethernet}}
 +
 +\\
 +\\
 +{{tag>Ethernet communication microcontroller ESP32 Arduino STM32F4 W5100 W5500 W6100 CH9120 ENC28J60 LAN8720 MAC PHY TCP/IP UART}}
 +\\
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