EID091-A701-S and EID091-A701-SC are newly launched industrial‑grade CAN FD‑to‑serial modules from EBYTE. Designed for complex bus interconnection and protocol conversion scenarios, they provide stable, high‑speed and flexible data interaction between CAN/CAN FD and serial interfaces, even in harsh industrial environments.

Overview of EID091-A701-S Series

The EID091-A701-S series targets industrial control, automotive electronics, fieldbus gateways, and remote data acquisition terminals that require data transmission or protocol conversion between CAN/CAN FD and serial ports. It can serve as a gateway node, protocol conversion node, or communication interface expansion module on user equipment.

Typical applications include:

  • Connecting legacy serial devices to CAN/CAN FD networks

  • Acting as a gateway between PLCs/upper computers and CAN field devices

  • Building distributed control networks for Modbus RTU devices over CAN/CAN FD

  • Implementing user‑defined application protocols across multi‑node bus networks

Key Features

  • Multi‑protocol support: Supports CAN FD and is backward‑compatible with CAN 2.0 A/B, and supports both ISO and Bosch CAN FD protocols, providing a unified hardware platform for both new designs and system upgrades.

  • Wide speed ranges:

    • Serial baud rate: 1200–3 Mbps, default 115200 bps

    • Arbitration domain baud rate: 5 K–1 Mbps, default 500 Kbps

    • Data domain baud rate: 100 K–5 Mbps, default 2 Mbps (invalid in pure CAN mode)

  • Flexible frame filtering: Supports configurable frame filtering to let users receive only key information in complex bus environments.

  • Industrial‑grade design: Operating temperature −40℃ to 85℃, operating humidity 10%–90% RH (non‑condensing), ensuring long‑term stable operation.

  • Five operating modes: Supports transparent conversion, transparent conversion with identifier, fixed‑format protocol conversion, Modbus protocol conversion, and custom protocol conversion to cover a wide range of application needs.

Hardware Design and Interfaces

The module adopts a stamp‑hole/SMT‑friendly package, making it easy to solder or mount onto user PCBs and greatly reducing hardware design difficulty.

Power and electrical characteristics:

  • Supply voltage: DC 4.5–5.5 V

  • Standby current: about 18 mA @ 5 V; TX/RX about 18.1 mA @ 5 V

  • Communication level: 3.3 V; level shifting is required when interfacing with 5 V systems.

Main pins (partial list):

  • VCC / GND: Module power supply pins

  • CANH / CANL: CAN FD bus differential high/low lines

  • TX3 / RX3: Open serial port pins, used as the communication interface to the host MCU or other serial devices

  • CFG: Hardware configuration‑mode pin, low level to enter configuration mode, high level to exit

  • RESTORE: Factory‑reset pin, pulling low for 5 seconds restores factory settings

  • RST: Active‑low reset input

  • EN: Reserved RS485 enable pin, can be connected directly to the RE/DE pin of an external RS485 transceiver

  • SET: Data status pin that outputs a low‑level indicator related to CAN bus data, convenient for system status monitoring.

Overview of Five Operating Modes

The EID091-A701-S / SC provides five flexible operating modes, making it easy to adapt to different system topologies and protocol requirements.

1) Transparent Mode

In transparent mode, the module does not modify the user data content. It only maps the data field between serial frames and CAN/CAN FD frames, effectively performing invisible format conversion between buses.

  • Serial → CAN/CAN FD: Data received from the serial port is filled sequentially into the CAN/CAN FD data field. Frame type and frame ID are taken from the user’s configuration and remain unchanged during conversion.

  • CAN/CAN FD → Serial: Data in the CAN/CAN FD data field is output sequentially to the serial frame. When the “frame information” and “frame ID” options are enabled, the corresponding information is also inserted into the serial frame.

Typical use cases:

  • Simple point‑to‑point or point‑to‑bus transmission where only data content matters, not frame IDs

  • Serial devices communicating with CAN nodes that use fixed frame IDs.

2) Transparent Mode with Identifier

This mode is an enhanced version of transparent mode, carrying CAN/CAN FD ID information within the serial frame and supporting automatic two‑way ID conversion. It is especially suitable for user‑defined application‑layer protocols in multi‑node networks.

  • Serial → CAN/CAN FD: The user reserves an ID field in the serial frame and configures its start position and length (1–2 bytes for standard frames, 1–4 bytes for extended frames). During conversion, the module parses this field and uses it as the CAN/CAN FD frame ID. Other data bytes are mapped into the CAN/CAN FD data field in order.

  • CAN/CAN FD → Serial: The received CAN/CAN FD frame ID is written into the specified ID position in the serial frame according to the configured address and length, and the rest of the data is forwarded sequentially.

Typical use cases:

  • Multi‑node communication where the serial side needs to dynamically control or identify CAN IDs

  • Custom bus protocols that require ID information to be transparent across serial and CAN/CAN FD.

3) Protocol Mode (Fixed Format)

Protocol mode provides fixed‑length serial representations for CAN and CAN FD frames, making it easier for upper‑layer software or MCUs to parse and assemble messages using a known, consistent format.

  • CAN format: Each CAN frame is represented by 13 bytes on the serial port (1 byte frame information + 4 bytes frame ID + 8 bytes data).

  • CAN FD format: Each CAN FD frame is represented by 69 bytes on the serial port (1 byte frame information + 4 bytes frame ID + 64 bytes data).

The frame information byte encodes:

  • FF: Standard vs. extended frame

  • RTR: Remote vs. data frame (must be 0 in CAN FD)

  • EDL: CAN vs. CAN FD

  • BRS: Bit‑rate switch flag (valid only in CAN FD)

  • DLC3–DLC0: Data length code.

In this mode, the actual frame ID and frame type come from the serial frame’s frame information and frame ID fields, rather than from the global configuration. This is ideal when:

  • The project requires strictly fixed frame formats

  • The host software is easier to implement with fixed‑length records.

4) Modbus Protocol Conversion Mode

In Modbus mode, the serial side uses the standard Modbus RTU format, while the CAN/CAN FD side uses a simple segment‑based format. This allows Modbus RTU data to be transmitted transparently over CAN/CAN FD.

  • Serial side: Frames must comply with the Modbus RTU specification. Frames that do not comply are discarded instead of being converted.

  • CAN/CAN FD side: Uses a “segment marker + segment type + segment counter” scheme to fragment and reassemble long Modbus messages. The first, intermediate, and last segments are clearly marked, and a 0–31 segment counter allows the receiver to detect missing segments.

  • The module does not act as a Modbus master or slave. It only validates, fragments, forwards, and reassembles Modbus RTU frames. After receiving all segments on the CAN/CAN FD side, it automatically rebuilds a complete Modbus RTU frame, appends CRC16, and sends it through the serial port.

Typical use cases:

  • Retrofitting Modbus RTU equipment into a CAN/CAN FD‑based distributed control network

  • Enhancing noise immunity and network scalability for existing Modbus RTU systems.

5) Custom Protocol Conversion Mode

Custom protocol mode is designed for advanced users who need full control over the serial frame format, enabling one‑to‑one mapping with proprietary or in‑house application protocols.

The serial frame consists of:

  • Frame header

  • Frame length (from the start of frame information to the last data byte, excluding the frame tail)

  • Frame information (0x00 for standard frames, 0x80 for extended frames)

  • Frame ID (2 bytes for standard frames, 4 bytes for extended frames, high byte first)

  • Data field

  • Frame trailer.

Conversion rules:

  • Serial → CAN/CAN FD: The module parses the serial frame strictly according to the custom format. If the header, tail, length, frame information, or other non‑data bytes are invalid, the frame will not be transmitted. Valid frames are mapped to CAN/CAN FD frames according to the specified frame information and ID, and the data field is copied into the CAN/CAN FD data field.

  • CAN/CAN FD → Serial: Each received CAN/CAN FD frame is forwarded immediately. The module adds frame header, frame length, frame information, frame ID and frame trailer to build a serial frame that conforms to the custom protocol.

Typical use cases:

  • Enterprise private protocols or legacy protocol stacks that must be preserved

  • Projects requiring strict control over every field of the frame format.

Configuration and Maintenance

The module supports configuration via AT commands and PC configuration tools. Users can flexibly set baud rates, frame filtering rules, operating modes, and other parameters. The RESTORE pin allows quick restoration of factory defaults, which is convenient for on‑site maintenance and batch deployment.