Chapter 195: CC-Link Protocol Implementation

Chapter Objectives

By the end of this chapter, you will be able to:

• Understand the fundamental principles and purpose of the CC-Link family of protocols.
• Differentiate between the various CC-Link versions, including CC-Link (serial), CC-Link IE Control, CC-Link IE Field, and CC-Link Safety.
• Describe the key characteristics of CC-Link, such as its master-slave architecture, cyclic communication, and data types.
• Outline the basic network topologies and communication mechanisms used in CC-Link networks.
• Recognize the hardware and software complexities associated with implementing CC-Link, especially for real-time Ethernet versions.
• Understand that direct implementation of a full CC-Link master or high-performance slave stack on an ESP32 is often impractical.
• Explore architectural approaches for an ESP32 to interact with a CC-Link network, typically by communicating with a CC-Link master controller (e.g., a PLC) or a gateway device.
• Identify common challenges when considering ESP32 integration with CC-Link systems.

Introduction

CC-Link (Control & Communication Link) is a family of open industrial network protocols that originated in Japan and is now widely adopted globally, particularly in factory automation and manufacturing. Developed and managed by the CC-Link Partner Association (CLPA), these networks are designed to facilitate reliable and efficient data exchange between controllers (like PLCs) and a wide array of field devices, including sensors, actuators, drives, and I/O modules.

The CC-Link family has evolved from traditional serial fieldbus (CC-Link) to high-speed, Ethernet-based networks (CC-Link IE), offering solutions for various levels of the automation pyramid, from simple bit-level I/O to complex controller-to-controller communication and synchronized motion control.

Implementing a full CC-Link master or a high-performance real-time slave, especially for the Industrial Ethernet (IE) versions, requires specialized hardware (ASICs/FPGAs) and certified software stacks due to stringent timing requirements and protocol complexity. Therefore, a general-purpose microcontroller like the ESP32 is typically not suited for direct, full-fledged participation as a master or a high-performance slave in these networks.

This chapter will provide a comprehensive overview of the CC-Link protocol family. We will then explore how an ESP32 can be strategically integrated into systems that utilize CC-Link. This usually involves the ESP32 acting in a supervisory capacity, as an HMI, a data logger, or a bridge, communicating with a dedicated CC-Link master (such as a Mitsubishi Electric PLC) or a gateway device using standard communication protocols. We will also touch upon the theoretical possibility of simpler slave implementations for specific CC-Link variants where software-based approaches might be considered.

Theory

What is CC-Link?

CC-Link stands for Control & Communication Link. It is a family of open-architecture industrial network protocols designed for high-speed, deterministic communication in automation systems. The CLPA (CC-Link Partner Association) manages the specifications and promotes interoperability through conformance testing.

The CC-Link Family

The CC-Link family includes several distinct network types, each tailored for different application needs:

1. CC-Link (Serial Fieldbus):
   • The original CC-Link, based on RS-485 physical layer.
   • Operates at speeds up to 10 Mbit/s.
   • Primarily designed for connecting PLCs to distributed I/O, intelligent devices, and drives.
   • Supports up to 64 stations on a bus topology.
   • Master-slave communication.
2. CC-Link LT (Bit-Oriented Network):
   • A simpler, bit-level network designed for connecting sensors and actuators (binary devices).
   • Reduces wiring complexity for discrete I/O.
   • Based on a master-slave principle.
3. CC-Link IE (Industrial Ethernet): This is the Ethernet-based evolution, offering higher speeds and larger data capacities.
   • CC-Link IE Control:
     • Gigabit Ethernet (1 Gbit/s) network for controller-to-controller communication (e.g., synchronizing multiple PLCs).
     • Uses a shared memory model for data exchange.
     • Typically employs a ring topology for redundancy.
   • CC-Link IE Field:
     • Gigabit Ethernet (1 Gbit/s) network for connecting controllers to field devices (drives, I/O, vision systems).
     • Offers high-speed, deterministic communication with large data capacity.
     • Supports various topologies (line, star, ring).
     • CC-Link IE Field Basic (SLMP): A software-based implementation option for CC-Link IE Field that uses standard TCP/IP (UDP) for cyclic communication. This makes it easier to implement on devices with standard Ethernet hardware but offers less determinism than the hardware-based versions. SLMP (Seamless Message Protocol) is a common message protocol used across CC-Link IE networks.
     • CC-Link IE Field Motion: A specialized version of CC-Link IE Field optimized for high-performance, synchronized multi-axis motion control. Requires dedicated hardware.
4. CC-Link Safety:
   • Extends CC-Link (serial) and CC-Link IE Field with functional safety capabilities.
   • Allows safety-related data (e.g., from emergency stops, light curtains) to be transmitted over the same network as standard control data, complying with international safety standards (e.g., IEC 61508 SIL3).
5. CSPP (CC-Link family Seamless Profile Protocol):
   • Not a network itself, but a profile definition that ensures common parameters and functionalities across different device types within the CC-Link family, simplifying integration and device replacement.

graph TD
    subgraph Legend
        direction LR
        L1(Origin)
        L2(Serial Branch)
        L3(Ethernet Branch)
        L4(Safety Layer)
        style L1 fill:#EDE9FE,stroke:#5B21B6,stroke-width:2px,color:#5B21B6
        style L2 fill:#DBEAFE,stroke:#2563EB,stroke-width:1px,color:#1E40AF
        style L3 fill:#D1FAE5,stroke:#059669,stroke-width:2px,color:#065F46
        style L4 fill:#FEE2E2,stroke:#DC2626,stroke-width:1px,color:#991B1B
    end

    A["CC-Link <br><b>(Original Serial Fieldbus)</b>"] --> B["CC-Link LT <br><i>(Simplified for Sensors/Actuators)</i>"];
    A --> C{Evolved to Industrial Ethernet};
    C --> D["CC-Link IE Control <br><b>(Controller-to-Controller)</b>"];
    C --> E["CC-Link IE Field <br><b>(Controller-to-Field)</b>"];
    A -.-> F["CC-Link Safety <br><i>(Functional Safety Extension)</i>"];
    E -.-> G["CC-Link Safety <br><i>(Functional Safety Extension)</i>"];
    E --> H["CC-Link IE Field Motion <br><i>(Synchronized Motion Control)</i>"];
    E --> I["CC-Link IE Field Basic <br><i>(Software-based via SLMP)</i>"];

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    classDef validation fill:#FEE2E2,stroke:#DC2626,stroke-width:1px,color:#991B1B;

    class A origin;
    class B,H,I process;
    class C decision;
    class D,E success;
    class F,G validation;

Key Characteristics of CC-Link Networks

• Master-Slave Architecture: Most CC-Link networks (especially serial CC-Link and CC-Link IE Field) operate on a master-slave principle. The master controller initiates communication and polls slave devices.
• Cyclic Communication: Time-critical data (I/O states, setpoints, actual values) are exchanged periodically in a deterministic manner. This ensures predictable update times.
• Transient (Acyclic) Communication: Allows for on-demand exchange of non-time-critical data like parameters, diagnostics, and program data.
• Data Types: Supports various data types, including:
  • Bit Data (RX/RY): For discrete inputs/outputs.
  • Word Data (RWw/RWr): For analog values, registers, parameters.
• Device Addressing: Each slave station on the network has a unique address or station number.
• Network Topologies:
  • CC-Link (Serial): Bus topology using RS-485. Terminators are required at both ends of the bus.
  • CC-Link IE: Supports line, star, and ring topologies using standard Ethernet cabling. Ring topology provides media redundancy. Integrated switch functionality in devices is common.
• High Reliability: Features like error detection, diagnostics, and (for IE ring topology) media redundancy contribute to high network availability.

CC-Link Communication Principles

1. CC-Link (Serial):

• Polling System: The master station cyclically polls each slave station.
• Link Scan: The master sends data to slaves and requests data from them in a predefined sequence.
• Data Areas:
  • Remote Inputs (RX): Bits sent from slave to master.
  • Remote Outputs (RY): Bits sent from master to slave.
  • Remote Word Write (RWw): Words sent from master to slave.
  • Remote Word Read (RWr): Words sent from slave to master.
• Frame Structure: Defined frame formats for data exchange, including addressing, data, and error checking (CRC).

2. CC-Link IE Field:

• Token Passing (Ring) or Master Control (Line/Star): While the underlying mechanism is Ethernet, the protocol ensures deterministic access.
• Cyclic Transmission: Uses dedicated Ethernet frames for cyclic data exchange at high speeds.
• Shared Memory Concept: Devices are assigned areas in a logical shared memory space, and the network ensures this memory is kept consistent across participants within the cycle time.
• SLMP (Seamless Message Protocol): A common application layer protocol used over UDP/IP or TCP/IP for acyclic communication and for cyclic communication in CC-Link IE Field Basic. It allows various devices to communicate using a standardized message format.

Hardware and Software Requirements

• CC-Link (Serial): Requires RS-485 transceivers. Master and slave devices need a CC-Link communication LSI (Large Scale Integration chip) or a software stack running on a capable microcontroller with appropriate RS-485 interface hardware.
• CC-Link IE Control/Field (Hardware-based): Requires Gigabit Ethernet PHYs and a dedicated CC-Link IE communication controller (ASIC or FPGA implementation) to handle the real-time Ethernet MAC, synchronization, and protocol processing.
• CC-Link IE Field Basic: Can be implemented in software using a standard Ethernet controller and a TCP/IP (UDP/IP) stack, as it relies on SLMP over UDP for cyclic data. This makes it more accessible for devices without specialized hardware but with trade-offs in performance and determinism compared to hardware-based CC-Link IE Field.
• Software Stacks: Implementing CC-Link often involves licensing a certified software stack from the CLPA or third-party providers, especially for official product development.

ESP32 and CC-Link

Direct implementation of a full-featured CC-Link master or a high-performance, hardware-based CC-Link IE Field slave on an ESP32 is generally not feasible or practical due to:

1. Stringent Real-Time Requirements (for many versions): Protocols like CC-Link (serial master) and hardware-based CC-Link IE Field have strict timing requirements for polling, frame processing, and synchronization that are difficult to meet reliably with a general-purpose MCU like the ESP32 running FreeRTOS and standard peripheral drivers.
2. Specialized Hardware Needs: Hardware-based CC-Link IE Field requires dedicated ASICs/FPGAs for its real-time Ethernet MAC. Serial CC-Link often uses specific LSIs for robust communication.
3. Protocol Stack Complexity and Certification: The full CC-Link protocol stacks are complex. Developing a compliant and certified stack from scratch is a significant undertaking. Licensed stacks are often tied to specific hardware platforms.

Plausible Roles for ESP32 in a CC-Link Environment:

1. Interfacing with a CC-Link Master (e.g., PLC):
   • The ESP32 can communicate with a CC-Link Master PLC using standard, non-real-time protocols that the PLC might also support (e.g., Modbus TCP, OPC UA, HTTP, MQTT via an additional communication module on the PLC or a gateway).
   • The ESP32 could act as an HMI, data logger, configuration tool, or bridge to cloud services, while the PLC handles all CC-Link network operations.
2. Component in a Gateway Device:
   • An ESP32 could manage the non-CC-Link side of a gateway. For example, a gateway might have a dedicated CC-Link interface (ASIC/FPGA) on one side and an ESP32 managing Wi-Fi/Ethernet/Cloud connectivity on the other, with the ESP32 handling data translation and routing.
3. Simple CC-Link IE Field Basic Slave (Conceptual):
   • Since CC-Link IE Field Basic uses SLMP over UDP/IP, it’s theoretically possible to implement a simple slave device using the ESP32’s standard Ethernet capabilities (either built-in MAC with external PHY for some ESP32 variants, or SPI-Ethernet bridge like W5500/ENC28J60).
   • This would still require implementing the SLMP protocol and managing the cyclic UDP communication. This is the most “direct” CC-Link participation an ESP32 might achieve without specialized external CC-Link hardware, but it’s limited to the “Basic” version and would be a non-trivial software project.

graph TD
    subgraph "Cloud / Enterprise Level"
        direction LR
        CLOUD["Cloud Services <br> (AWS/Azure/etc)"]
    end
    
    subgraph "Supervisory / Local Network (Wi-Fi/Ethernet)"
        direction LR
        ESP32(ESP32 <br> HMI / Data Logger /<br> Cloud Gateway)
    end
    
    subgraph "Control Level (CC-Link Master)"
        PLC[CC-Link Master PLC]
    end

    subgraph "Field Level (Real-Time Network)"
        direction LR
        net((CC-Link IE Field Network))
        DEV1["Slave Device 1<br>(Sensor)"]
        DEV2["Slave Device 2<br>(Actuator)"]
        DEV3["Slave Device 3<br>(Drive)"]
    end

    ESP32 -- "MQTT, HTTP, <br> Modbus TCP, OPC UA" --> PLC;
    PLC --- net;
    net --- DEV1;
    net --- DEV2;
    net --- DEV3;
    ESP32 -- "Wi-Fi/Ethernet" --> CLOUD;
    
    linkStyle 0 stroke-width:2px,stroke:blue,color:blue;
    linkStyle 4 stroke-width:2px,stroke:purple,color:purple;

    classDef esp fill:#EDE9FE,stroke:#5B21B6,stroke-width:2px,color:#5B21B6;
    classDef plc fill:#D1FAE5,stroke:#059669,stroke-width:2px,color:#065F46;
    classDef device fill:#DBEAFE,stroke:#2563EB,stroke-width:1px,color:#1E40AF;
    classDef cloud fill:#FEF3C7,stroke:#D97706,stroke-width:1px,color:#92400E;
    
    class ESP32 esp;
    class PLC plc;
    class DEV1,DEV2,DEV3 device;
    class CLOUD cloud;

Practical Examples (Conceptual)

The examples here are conceptual, focusing on how an ESP32 might interact with a system that uses CC-Link, rather than direct CC-Link protocol implementation by the ESP32 itself (unless considering a very simplified CC-Link IE Field Basic slave).

Assumptions:

• A Mitsubishi Electric PLC (or similar) is acting as the CC-Link Master.
• The PLC provides a way to access some of its data or trigger actions via a standard protocol like Modbus TCP (often available on PLCs or via add-on modules).
• The ESP32 has Ethernet or Wi-Fi connectivity.

Code Snippet 1: Reading Data from a CC-Link Master PLC via Modbus TCP (Conceptual)

The ESP32 acts as a Modbus TCP client to read data registers from a PLC. These registers in the PLC might be mapped to data coming from CC-Link slave devices.

#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_log.h"
#include "esp_wifi.h"
#include "nvs_flash.h"
#include "esp_netif.h"
// For a real Modbus TCP client, you'd use a library like freemodbus (in client mode)
// or another Modbus TCP client library compatible with ESP-IDF.
// This example will be highly simplified and conceptual for TCP socket communication.
#include "lwip/sockets.h"
#include "lwip/netdb.h" // For gethostbyname

// Assume wifi_connect.h and its implementation are available for Wi-Fi setup
// #include "wifi_connect.h"

static const char *TAG = "CCLINK_MODBUS_IF";

#define PLC_IP_ADDRESS "192.168.1.50" // IP Address of the PLC (Modbus TCP Server)
#define PLC_MODBUS_PORT 502          // Standard Modbus TCP port

// Simplified Modbus RTU over TCP frame for Read Holding Registers (Function Code 0x03)
// Transaction ID (2 bytes), Protocol ID (2 bytes, 0x0000 for Modbus)
// Length (2 bytes, number of bytes following)
// Unit ID (1 byte)
// Function Code (1 byte)
// Starting Address (2 bytes)
// Quantity of Registers (2 bytes)

// Example: Read 2 holding registers starting from address 0 (e.g., D0, D1 in Mitsubishi PLC)
// Transaction ID: 0x0001
// Protocol ID:    0x0000
// Length:         0x0006 (UnitID + FC + StartAddr + Quantity)
// Unit ID:        0x01 (or 0xFF for some PLCs)
// Function Code:  0x03
// Start Address:  0x0000
// Quantity:       0x0002
const uint8_t modbus_read_req[] = {
    0x00, 0x01, // Transaction ID
    0x00, 0x00, // Protocol ID
    0x00, 0x06, // Length
    0x01,       // Unit ID
    0x03,       // Function Code
    0x00, 0x00, // Starting Address
    0x00, 0x02  // Quantity of Registers
};

void read_plc_data_via_modbus_task(void *pvParameters) {
    char rx_buffer[128];
    struct sockaddr_in dest_addr;

    // Wait for Wi-Fi connection (conceptual delay)
    vTaskDelay(pdMS_TO_TICKS(10000));
    ESP_LOGI(TAG, "Wi-Fi connected. Attempting to connect to PLC Modbus TCP server.");

    dest_addr.sin_addr.s_addr = inet_addr(PLC_IP_ADDRESS);
    dest_addr.sin_family = AF_INET;
    dest_addr.sin_port = htons(PLC_MODBUS_PORT);

    int sock = socket(AF_INET, SOCK_STREAM, IPPROTO_IP);
    if (sock < 0) {
        ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
        vTaskDelete(NULL);
        return;
    }
    ESP_LOGI(TAG, "Socket created, connecting to %s:%d", PLC_IP_ADDRESS, PLC_MODBUS_PORT);

    int err = connect(sock, (struct sockaddr *)&dest_addr, sizeof(dest_addr));
    if (err != 0) {
        ESP_LOGE(TAG, "Socket unable to connect: errno %d", errno);
        close(sock);
        vTaskDelete(NULL);
        return;
    }
    ESP_LOGI(TAG, "Successfully connected to PLC.");

    while(1) {
        err = send(sock, modbus_read_req, sizeof(modbus_read_req), 0);
        if (err < 0) {
            ESP_LOGE(TAG, "Error occurred during sending: errno %d", errno);
            break;
        }

        int len = recv(sock, rx_buffer, sizeof(rx_buffer) - 1, 0);
        // Poll response
        if (len < 0) {
            ESP_LOGE(TAG, "recv failed: errno %d", errno);
            break;
        } else if (len == 0) {
            ESP_LOGI(TAG, "Connection closed by PLC");
            break;
        } else {
            rx_buffer[len] = 0; // Null-terminate whatever we received
            ESP_LOGI(TAG, "Received %d bytes from PLC:", len);
            ESP_LOG_BUFFER_HEXDUMP(TAG, rx_buffer, len, ESP_LOG_INFO);

            // Basic Modbus TCP response validation (conceptual)
            // Expected response for 2 registers (4 bytes data):
            // Trans ID (2), Proto ID (2), Length (2, e.g. 0x0005 for 1 byte UnitID + 1 byte FC + 1 byte ByteCount + 4 bytes Data)
            // Unit ID (1), FC (1), Byte Count (1, e.g. 0x04 for 4 data bytes), Data (N bytes)
            if (len >= 9 && rx_buffer[7] == 0x03 /* FC */ && rx_buffer[8] == 0x04 /* Byte Count for 2 registers */) {
                uint16_t reg1_val = (rx_buffer[9] << 8) | rx_buffer[10];
                uint16_t reg2_val = (rx_buffer[11] << 8) | rx_buffer[12];
                ESP_LOGI(TAG, "Register 1 (D0) Value: %u (0x%04X)", reg1_val, reg1_val);
                ESP_LOGI(TAG, "Register 2 (D1) Value: %u (0x%04X)", reg2_val, reg2_val);
            } else {
                ESP_LOGW(TAG, "Received Modbus response format not as expected for read holding registers.");
            }
        }
        vTaskDelay(pdMS_TO_TICKS(5000)); // Poll every 5 seconds
    }

    ESP_LOGE(TAG, "Shutting down socket and deleting task...");
    close(sock);
    vTaskDelete(NULL);
}


void app_main(void) {
    esp_err_t ret = nvs_flash_init();
    if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
      ESP_ERROR_CHECK(nvs_flash_erase());
      ret = nvs_flash_init();
    }
    ESP_ERROR_CHECK(ret);
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());

    // Initialize Wi-Fi (replace with your actual Wi-Fi connection logic)
    // Example: wifi_connect_sta("your_ssid", "your_password");

    ESP_LOGI(TAG, "ESP32 CC-Link/Modbus Interface Application Started.");
    // xTaskCreate(read_plc_data_via_modbus_task, "modbus_read_task", 4096*2, NULL, 5, NULL);
}

Explanation:

• This code demonstrates a highly simplified Modbus TCP client. In a real application, you would use a robust Modbus library.
• The ESP32 connects to a PLC (acting as Modbus TCP server) and sends a request to read holding registers.
• These registers on the PLC could be mapped to data originating from devices on its CC-Link network.
• The ESP32 is using standard TCP/IP sockets for communication, not directly interacting with CC-Link.
• This is not a full Modbus client. It lacks proper error handling, transaction ID management, and support for various Modbus functions.

Build and Run (Conceptual)

1. Setup:
   • A Wi-Fi network for the ESP32.
   • A Modbus TCP server (e.g., a PLC or a simulator like ModRSsim2) configured with some holding register values. Ensure the IP address and port match.
2. Build: idf.py build
3. Flash & Monitor: idf.py -p (PORT) flash monitor
4. Observe:
   • Wi-Fi connection logs.
   • Logs from the ESP32 attempting to connect to the Modbus server.
   • If successful, logs of the Modbus request being sent and the response received, including the parsed register values.

Variant Notes

For the supervisory or gateway roles described, ESP32 variant selection depends on connectivity and processing needs:

• ESP32, ESP32-S3: Good choices due to dual cores, ample memory, and built-in Wi-Fi/Bluetooth. The original ESP32 has an Ethernet MAC (needs PHY), and ESP32-S3 can use SPI-Ethernet for wired connections. These are suitable for running TCP/IP stacks, Modbus client/server libraries, MQTT clients, etc.
• ESP32-S2: Single-core with Wi-Fi. Capable for less demanding supervisory tasks.
• ESP32-C3, ESP32-C6, ESP32-H2: RISC-V based, with Wi-Fi and/or Bluetooth (C6/H2 also have 802.15.4). Suitable for applications where they act as clients to a more powerful CC-Link master system.

Key Considerations for All Variants in this Context:

1. Network Interface: A reliable Wi-Fi or Ethernet connection is key for communicating with the CC-Link master system or gateway.
2. Software Libraries: Availability and resource requirements of libraries for protocols like Modbus TCP, MQTT, HTTP, or SLMP (if attempting CC-Link IE Field Basic) are important.
3. No Direct CC-Link Real-Time Capability: Reiterate that these variants cannot directly implement the time-critical aspects of most CC-Link versions. Their role is indirect.

Common Mistakes & Troubleshooting Tips

1. Assuming Direct ESP32 CC-Link Master/Slave Capability:
   • Mistake: Trying to find low-level ESP-IDF drivers for CC-Link serial or CC-Link IE Field hardware-based communication.
   • Fix: Understand that these require specialized ASICs/FPGAs and certified stacks. ESP32’s role is typically at a higher application layer, interacting with a dedicated CC-Link interface or master.
2. Incorrect Network Configuration for Indirect Communication:
   • Mistake: IP address conflicts, wrong subnet masks, incorrect port numbers when ESP32 tries to communicate with a PLC or gateway over Ethernet/Wi-Fi.
   • Fix: Verify all IP network settings on the ESP32 and the target device (PLC, gateway). Use tools like ping or network scanners to check basic connectivity.
3. Protocol Implementation Errors (e.g., Modbus, MQTT, SLMP):
   • Mistake: Incorrectly formatting messages, misinterpreting responses, or errors in state management when using protocols like Modbus TCP or SLMP to talk to a CC-Link master or device.
   • Fix: Use established libraries for these protocols where possible. If implementing from scratch (e.g., for SLMP), meticulously follow the protocol specifications. Use Wireshark or other network analyzers to inspect traffic.
4. Ignoring CC-Link System State and Diagnostics:
   • Mistake: The ESP32 application sends commands or expects data without considering the operational state of the CC-Link network or the master PLC (e.g., PLC in STOP mode, CC-Link network error).
   • Fix: Design the ESP32 application to also query status information from the PLC/gateway. Implement robust error handling and state synchronization.
5. Underestimating CC-Link IE Field Basic Complexity:
   • Mistake: Thinking CC-Link IE Field Basic is trivial because it’s “software-based” over UDP.
   • Fix: While more accessible than hardware versions, implementing a compliant SLMP stack for cyclic UDP communication, managing device profiles, and ensuring interoperability for CC-Link IE Field Basic is still a complex software task.

Exercises

1. Research CC-Link Interface Options:
   • Identify one example of a dedicated CC-Link (serial) interface LSI/chip and one example of a CC-Link IE Field (hardware-based) controller ASIC/FPGA solution.
   • Briefly describe their key features and typical host interface (e.g., SPI, parallel bus).
2. Conceptual Design: ESP32 as an SLMP Client for CC-Link IE Field Basic:
   • Imagine an ESP32 needs to read I/O data from a third-party device that acts as a CC-Link IE Field Basic slave (SLMP server over UDP).
   • Outline the main steps and data structures the ESP32 application would need to:
     1. Establish UDP communication.
     2. Send an SLMP message to read remote I/O (RX bits).
     3. Receive and parse the SLMP response.
   • What are the potential challenges in implementing this robustly?
3. CC-Link vs. Modbus:
   • Create a brief comparison between CC-Link (serial) and Modbus RTU, focusing on:
     • Typical application areas.
     • Maximum speed.
     • Data types supported.
     • Typical master/slave capabilities.

Summary

• CC-Link is a family of open industrial networks (serial and Ethernet-based) for control and communication, managed by the CLPA.
• Versions include CC-Link (serial), CC-Link LT, CC-Link IE Control, CC-Link IE Field (including IE Field Basic and IE Field Motion), and CC-Link Safety.
• They typically use a master-slave architecture with cyclic data exchange for I/O and control, and acyclic communication for parameters/diagnostics.
• Direct implementation of CC-Link master or high-performance real-time slave protocols on an ESP32 is generally not feasible due to hardware and timing constraints.
• An ESP32 can integrate with CC-Link systems by communicating with a dedicated CC-Link Master (PLC) or gateway using standard protocols (Modbus TCP, MQTT, HTTP).
• CC-Link IE Field Basic, using SLMP over UDP/IP, offers a theoretical path for software-based slave implementation on devices like ESP32 with standard Ethernet, but it’s still complex.
• Understanding the ESP32‘s role as a supervisory or ancillary component, rather than a direct real-time network participant, is key for successful integration.

Further Reading

• CC-Link Partner Association (CLPA): https://www.cc-link.org/ or regional CLPA websites (e.g., CLPA-Europe, CLPA-Americas). (Official specifications, technical resources, partner product catalogs).
• Mitsubishi Electric Factory Automation: (Mitsubishi Electric is a primary promoter and user of CC-Link, their documentation often contains detailed information on CC-Link products and implementation).
• SLMP (Seamless Message Protocol) Specifications: (Available from CLPA, crucial for CC-Link IE Field Basic).
• ESP-IDF API Reference (for networking components like Sockets, HTTP Client, MQTT): https://docs.espressif.com/projects/esp-idf/en/v5.4/ (refer to relevant protocol sections).