RS232/485/422 TO CAN

RS232 RS485 RS422 TO CAN

Overview

Introduction

RS232/485/422 TO CAN is an industrial-grade RS232/485/422 to CAN isolated converter. It features built-in power isolation, ADI magnetic coupling isolation, TVS, and other protection circuits, with an industrial guide rail case. RS232/485/422 TO CAN is easy to operate, with zero-delay automatic send/receive conversion. It possesses characteristics such as fast communication speeds, stability, reliability, and security, making it suitable for various industrial control devices or applications with high communication requirements.

Features

Adopts SP3232EEN + SP485EEN chips, stable and high-speed communication, with better compatibility.
Onboard unibody power supply isolation, provides stable isolated voltage and needs no extra power supply for the isolated terminal.
Onboard unibody digital isolation, allows signal isolation, high reliability, strong anti-interference, and low power consumption.
Compliant with CAN 2.0B (extended frame) specification, compatible with CAN 2.0A (standard frame) specification; Compliant with ISO 11898-1/2/3 standard.
CAN baud rate: 10kbps~1000kbps, configurable CAN baud rate.
High-speed conversion: At a serial port baud rate of 115200 and CAN rate of 250kbps, the CAN sending speed can reach up to 1270 extended frames per second（Close to the theoretical maximum of 1309 extended frames per second）.
Supports data communication and conversion between RS232/485/422 and CAN interfaces.
Supports 4 operating modes: transparent conversion, transparent with identifiers conversion, format conversion, and Modbus RTU protocol conversion.
Onboard TVS (Transient Voltage Suppressor), effectively suppresses surge voltage and transient spike voltage in the circuit, lightningproof & anti-electrostatic.
Onboard self-recovery fuse and protection diodes, ensure the current/voltage stable outputs, provide over-current/over-voltage proof, and improve shock resistance.
Onboard 15KV ESD isolation protection and 600W lightningproof & anti-surge protection.
Onboard 120R terminal resistor on the RS485/RS422 port, configurable by jumper.
Supports device firmware upgrade via RS232/485/422, more convenient for firmware customization.
Supports setting operation parameters via configuration software or serial commands, capable of saving settings after powering off.
Onboard power supply screw terminal, allows 5V~36V DC wide-range input.
4 LEDs for indicating the power and transceiver status.
Industrial grade metal case, supports wall-mount and rail-mount installation, solid and beautiful, easy to install.

Parameters

Product	Industrial isolated RS232/485/422 TO CAN
Host Interface	CAN
Device Interface	RS232/485/422
CAN Interface	Baud Rate	10kbps~1000kbps
	Direction Control	Hardware automatic control
	Resistor	Default 120R
	Interface	Screw terminal
	CAN Interface	H, L, GND
RS232/485/422 Interface	Baud Rate	1200bps ~ 460800bps
	Direction Control	Hardware automatic control
	Resistor	Onboard reserved 120R matching resistor, NC by default, enabled via jumpers
	RS232 Interface	DB9 Interface
	RS485/422 Interface	Screw terminal
	RS485 Interface	A+, B-, GND
	RS422 Interface	TA, TB, RA, RB, GND
	Protection	Provides 600W of lightning, surge, and 15KV static protection (on-board 120R balancing resistor)
	Transmission Mode	Point-to-multipoints (up to 32 nodes, it is recommended to use repeaters for 16 nodes or more)
Button	Press and hold for 1 second	Reset the system
Button	Press and hold for 5 seconds	Restore Factory Status
Indicator	PWR	Red power indicator, lights up when voltage is detected
	RUN	Operation status indicator, normal operation blinks at 1-second intervals
	COM	CAN blue TX indicator, lights up when the CAN port sends data RS232/485/422 blue RX indicator, lights up when RS232/285/422 port receives data
	CAN	CAN blue RX indicator, lights up when CAN port receives data RS232/485/422 blue TX indicator, lights up when RS232/485/422 port sends data
Environment	Temperature range	-10℃ ~70℃

Interface Introduction

Dimensions

Default Factory Settings

Item	Parameter
RS232/485/422	115200,8,N,1
CAN working mode	Transparent conversion, bidirectional
CAN baud rate	250kbps
Type of frame CAN sends	Extended frame
Frame ID CAN sends	0x12345678
CAN filter	Prohibition(Accept all CAN frames)

Device Configuration

Use USB TO 4CH Serial Converter (or USB to RS232, USB to RS485 or USB to RS422) for initial configuration. No configuration is performed, and the factory settings are maintained.

Hardware Connection

Connect USB to RS232/485/422 device (the following shows RS485 interface connection of USB TO 4CH Serial Converter):

RS232/485/422 TO CAN - RS485	USB TO 4CH Serial Converter - Port C
RS485 - GND	Port C - GND
RS485 - A+	Port C - A+
RS485 - B-	Port C - B-

Software Operation

Open SSCOM, view the COM port used, and perform it with the COM42:

Open WS-CAN-TOOL

Select the language:

Select the COM port corresponding to the connected RS232/485/422, and then open the serial port:

Click on Read Device Parameters.

If you need to modify the device parameters, you can directly modify it and click on "Save Device Parameters", and then click on "Restart Device" (for example, modifying CAN ID):

Module Usage Explanation

Transparent Conversion

*In this mode, the converter promptly sends the received data from one bus to the other bus.

Serial Frame To CAN

The entire data of a serial frame is sequentially filled into the data field of a CAN message frame. Upon receiving a frame of data from the serial bus, the converter promptly transmits it to the CAN bus. The converted CAN message frame information (frame type section) and frame ID are pre-configured by the user and remain unchanged throughout the conversion process.
The format of the data conversion is illustrated in the diagram below.

If the length of the received serial frame is less than or equal to 8 bytes, characters from 1 to n (where "n" is the length of the serial frame) are sequentially filled into positions 1 to n in the data field of the CAN message (as depicted in the illustration where "n" is 7).
If the number of bytes in the serial frame is greater than 8, the processor starts from the first character of the serial frame and fills the first set of 8 characters sequentially into the data field of the CAN message. After transmitting this data onto the CAN bus, it proceeds to convert the remaining serial frame data and fills the CAN message's data field until all the data has been converted.
For example, in the CAN parameter settings, if "Standard Frame" is chosen and the CAN ID is filled with 00000060, note that only the last 11 bits are valid for standard frames. The converted CAN data appears as follows:

CAN Frame To UART

For the CAN bus, it promptly sends a frame after receiving a frame.
When converting, all the data in the CAN message field is converted to the serial frame in order, and the corresponding data format is shown below:

If during configuration, the "Convert CAN Message to Serial" option is enabled, the converter will directly fill the "Frame Information" byte(s) of the CAN message into the serial frame.
Similarly, if the "Convert CAN Frame ID to Serial" option is enabled, it will fill all the "Frame ID" byte(s) of the CAN message into the serial frame.
For instance, if "Convert CAN Message to Serial" is enabled but "Convert CAN Frame ID to Serial" is not, the CAN frame converted to serial appears as illustrated below:

Transparent Conversion With ID

Transparent conversion with ID is a specialized use of transparent conversion that facilitates users in constructing their networks more conveniently and employing custom application protocols.
This method automatically converts the address information from a serial frame into the frame ID of the CAN bus. By informing the converter about the starting address and length of this address in the serial frame during configuration, the converter extracts this frame ID during conversion and fills it into the frame ID field of the CAN message. This serves as the ID of the CAN message when forwarding this serial frame. When converting a CAN message into a serial frame, the ID of the CAN message is also translated into the respective position within the serial frame. It's important to note that, in this conversion mode, the "CAN ID" setting in the "CAN Parameter Settings" of the configuration software is invalid. This is because, in this scenario, the transmitted identifier (frame ID) is populated from the data within the aforementioned serial frame.

UART to CAN

Upon receiving a complete serial data frame, the converter promptly forwards it to the CAN bus.
The CAN ID carried within the serial frame can be set within the configuration, specifying its starting address and length within the serial frame. The range for the starting address is from 0 to 7, while the length ranges from 1 to 2 for standard frames and 1 to 4 for extended frames.
During conversion, based on the pre-configured settings, all CAN frame IDs within the serial frame are entirely translated into the frame ID field of the CAN message. If the number of frame IDs within the serial frame is fewer than the number of frame IDs within the CAN message, the filling sequence in the CAN messages is frames ID1 to ID4, with the remaining IDs filled with "0". The rest of the data undergoes sequential conversion as shown in the diagram.
If a single CAN message frame does not complete the conversion of the serial frame data, the same ID continues to be used as the frame ID for the CAN message to convert until the entire serial frame has been completely converted.

For example, the initial address of the CAN ID in the serial frame is 0, the length is 3 (in the extended frame), and the serial frame and the converted CAN message are as shown below. Note that the two frames of CAN messages are converted in the same ID.

CAN Frame to UART

If the initial address of the configured CAN ID is 0 in the serial frame and a length of 3 (in the case of extended frames), the CAN message and the result of converting it to a serial frame are shown below:

Format Conversion

This is the simplest mode of use and the data format is agreed to be 13 bytes, which contains all the information of the CAN frame.

Conversion Explanation

Data conversion format as shown below. Each CAN frame includes 13 bytes, and they include CAN information + ID + data.

Modbus Protocol Conversion

Convert the standard Modbus RTU serial data protocol to the specified CAN data format, and this conversion generally requires the editable CAN bus device message.
The serial data must be compliant with the standard Modbus RTU protocol, otherwise it can not be converted. Please note that CRC parity can not be converted to CAN.
The CAN formulates a simple and efficient segment communication format to realize Modbus RTU communication, which does not differentiate between host and slave, and users only need to communicate according to the standard Modbus RTU protocol.
The CAN does not require CRC checksum, and after the converter receives the last CAN frame, the CRC will be added automatically. Then, a standard Modbus RTU data packet is formed and sent to the serial port.
In this mode, the [CAN ID] of the [CAN Parameter Setting] of the configuration software is invalid, because the identifier (frame ID) sent at this time is filled by the address field (node ID) in the Modbus RTU serial frame.

Serial Frame Format (Modbus RTU)

Serial parameter: baud rate, data bits, stop bits, and parity bits can be set via configuration software.
The data protocol needs to conform to the standard Modbus RTU protocol.

CAN Frame Format

The CAN side designs a set of segment protocol formats, which defines a method for segmenting and reorganizing a message that is greater than 8 bytes in length, as shown below.
Note that when the CAN frame is a single frame, the segmentation flag bit is 0x00.

The CAN frame message can be set by the configuration software (remote or data frame; standard or extended frame).
The transmitted Modbus protocol starts from "Data 2" byte, if the protocol content is more than 7 bits, and the rest of the protocol content is converted in this segmented format until the conversion is complete.
Data 1 is a segmentation control message (1 byte, 8bit), and the meaning is shown below:

Segmentation Mark
The segmentation mark occupies one bit (Bit7) and indicates whether the message is segmented or not. "0" indicates a separate message, and "1" indicates a frame in a segmented message.
Segmentation Type
The segmentation type occupies 2 Bits (Bit6, Bit5), and indicates the types of the message in this segment message.

Segmentation Counter
Occupies 5 bits (Bit4-Bit0), used to distinguish the serial number of segments in the same frame Modbus message, enough to verify whether the segments of the same frame are complete.

Conversion Example

The serial port side Modbus RTU data (in hex).

01 03 14 00 0A 00 00 00 00 00 14 00 00 00 00 00 17 00 2C 00 37 00 C8 4E 35

The first byte 01 is the Modbus RTU address code, converted to CAN ID.7-ID.0;
The last 2 bytes (4E 35) are Modbus RTU CRC checksums, which are discarded and not converted.
The final conversion to the CAN data message is as follows:
Frame 1 CAN message: 81 03 14 00 0A 00 00 00 00
Frame 2 CAN message: a2 00 00 14 00 00 00 00 00
Frame 3 CAN message: a3 00 17 00 2C 00 37 00
Frame 4 CAN message: c4 c8
The frame type (standard or extended frame) of the CAN messages is set via the configuration software;
The first data of each CAN message is filled with segmented information (81, a2, a3, and c4), which is not converted into Modbus RTU frames, but only serves as acknowledgment control information for the message.

The conversion principle of data from the CAN side to ModBus RTU is the same as the above, after the CAN side receives the above four messages, the converter will combine the received CAN messages into a frame of RTU data according to the CAN segmentation mechanism mentioned above, and add CRC checksum at the end.

Verify the Function

RS232 TO CAN Test

Use USB-CAN-A and USB TO 4CH Serial Converter to demonstrate.

Hardware Connection

Connect to the CAN device:

RS232/485/422 TO CAN - CAN	USB-CAN-A
CAN - CAN H	CAN - CAN H
CAN - CAN L	CAN - CAN L
CAN - CAN G	CAN - GND

Connect to RS232 device

RS232/485/422 TO CAN - RS232	USB TO 4CH Serial Converter - Port D
RS232 - GND	Port D - GND
RS232 - TXD	Port D - RXD
RS232 - RXD	Port D - TXD

Software Operation

Open USB-CAN-A-TOOL.
Select the corresponding COM port of the USB-CAN-A, and click on "Open".

Select the baud rate of the CAN device as 250kbps, click on "Set and Start" , input the data to send, and select "Cycle".

Open an SSCOM, select the corresponding COM port of the USB TO 4CH Serial Converter's Port D, and open the serial port.

In the SSCOM software, check "Hexshow", "sendHex" and "Show Time and Package", input the data to be sent.

11 22 33 44 55 66 77 88

Select data in USB-CAN-A_TOOL, click on "Send selected frame".

And then you can see that it transmits and receives.

Or you can click on "Send every...ms/Time".

And then you can see that it transmits and receives.

RS485 TO CAN Test

Use USB-CAN-A and USB TO 4CH Serial Converter to demonstrate.

Hardware Connection

Connect to the CAN device.

RS232/485/422 TO CAN - CAN	USB-CAN-A
CAN - CAN H	CAN - CAN H
CAN - CAN L	CAN - CAN L
CAN - CAN G	CAN - GND

Connect to the RS485 device.

RS232/485/422 TO CAN - RS485	USB TO 4CH Serial Converter - Port C
RS485 - GND	Port C - GND
RS485 - A+	Port C - A+
RS485 - B-	Port C - B-

Software Operation

Open USB-CAN-A-TOOL.
Select the corresponding COM port of the USB-CAN-A, and click on "Open".

Select the baud rate of the CAN device as 250kbps, click on "Set and Start" , input the data to send, and select "Cycle".

Open an SSCOM, select the corresponding COM port of the USB TO 4CH Serial Converter's Port C, and open the serial port.

In the SSCOM software, check "Hexshow", "sendHex" and "Show Time and Package", input the data to be sent.

11 22 33 44 55 66 77 88

Select data in USB-CAN-A_TOOL, click on "Send selected frame".

And then you can see that it transmits and receives.

Or you can click on "Send every...ms/Time".

And then you can see that it transmits and receives.

RS422 TO CAN Test

Use USB-CAN-A and USB TO 4CH Serial Converter to test the functions.

Hardware Connection

Connect to CAN device:

RS232/485/422 TO CAN - CAN	USB-CAN-A
CAN - CAN H	CAN - CAN H
CAN - CAN L	CAN - CAN L
CAN - CAN G	CAN - GND

Connect to RS422 device

RS232/485/422 TO CAN - RS422	USB TO 4CH Serial Converter - Port C
RS422 - GND	Port C - GND
RS422 - TA	Port C - RA
RS422 - TB	Port C - RB
RS422 - RA	Port C - TA
RS422 - RB	Port C - TB

Software Operation

Open USB-CAN-A-TOOL.
Select the corresponding COM port of the USB-CAN-A, and click on "Open".

Select the baud rate of the CAN device as 250kbps, click on "Set and Start" , input the data to send, and select "Cycle".

Open an SSCOM, select the corresponding COM port of the USB TO 4CH Serial Converter's Port C, and open the serial port.

In the SSCOM software, check "Hexshow", "sendHex" and "Show Time and Package", input the data to be sent.

11 22 33 44 55 66 77 88

Select data in USB-CAN-A_TOOL, click on "Send selected frame".

And then you can see that it transmits and receives.

Or you can click on "Send every...ms/Time".

And then you can see that it transmits and receives.

RS485 CAN HAT Expansion

RS485 CAN HAT Related User's Guide.
Please understand the usage of RS485 CAN HAT first.

Interface Expansion

CAN Interface Expansion

Connect to RS485 interface, and the RS485 CAN HAT expands as 2x CAN interfaces.

RS232/485/422 TO CAN - RS485	RS485 CAN HAT
RS485 - A+	RS485 - A+
RS485 - B-	RS485 - B-

RS232/485/422 Interface Expansion

Connect to the CAN interface, and then the RS485 CAN HAT expands as 1x RS485 interface and 1x RS232/RS485/422 interface.

RS232/485/422 TO CAN - CAN	RS485 CAN HAT
CAN - CAN H	CAN - CAN H
CAN - CAN L	CAN - CAN L

Example

Use RS232/485/422 TO CAN for the communication between RS485 and CAN of RS485 CAN HAT.

Hardware Connection

RS232/485/422 TO CAN - RS485	RS485 CAN HAT
CAN - CAN H	CAN - CAN H
CAN - CAN L	CAN - CAN L
RS485 - A+	RS485 - A+
RS485 - B-	RS485 - B-

Software Operation

Preparation

Connect the RS485 CAN HAT to the Raspberry Pi, and modify the boot script "config.txt".

sudo nano /boot/config.txt

Add the following content at the last line:

dtparam=spi=on
dtoverlay=mcp2515-can0,oscillator=12000000,interrupt=25,spimaxfrequency=2000000

Also find the following configuration statement in /boot/config.txt to enable the serial port, or add it to the end of the file if it is not there.

enable_uart=1

Install Library

The following operation is required.
Install can-units

sudo apt-get install can-utils

Install wiringpi environment

#Open the Raspberry Pi terminal and run the following commands  
cd
sudo apt-get install wiringpi
#For Raspberry Pi systems after May 2019 (earlier may not be performed), an upgrade may be required: 
wget https://project-downloads.drogon.net/wiringpi-latest.deb
sudo dpkg -i wiringpi-latest.deb
gpio -v
#Running gpio -v will bring up version 2.52, if it doesn't it means there was an installation error

Install Python Environment

sudo apt-get update
sudo apt-get install python3-pip
sudo apt-get install python-serial

Configure the running environment

sudo pip install python-can

If running the above commands fails, you can download the following image:

sudo pip install -i https://pypi.tuna.tsinghua.edu.cn/simple python-can
sudo pip install -i https://mirrors.aliyun.com/pypi/simple python-can
sudo pip install -i https://pypi.mirrors.ustc.edu.cn/simple python-can

Modify RS232/485/422 TO CAN Configuration

Use the software to modify the CAN id of the RS232/485/422 TO CAN.
Set the CAN ID as "123", and operate it by following the #Device Configuration

C Example

If you have already downloaded, please skip the file deletion step and the program download step (the two steps below).
Delete the previously downloaded package.

Please note: If you want to keep the original RS485_CAN_HAT_Code file, please copy it to another path.

cd
rm -rf RS485_CAN_HAT_Code.zip
rm -rf RS232-485-422_Code.zip
rm -rf RS485_CAN_HAT_Code
sudo ifconfig can0 down

Download the example demo:

cd
sudo apt-get install unzip
wget https://files.waveshare.com/wiki/RS232-485-422-TO-CAN/RS232-485-422_Code.zip
unzip RS232-485-422_Code.zip
sudo chmod 777 -R RS485_CAN_HAT_Code/

CAN sends and the RS485 receives:

cd
cd RS485_CAN_HAT_Code/CAN_TO_RS485/wiringPi/
make clean
make
sudo ./can_send

RS485 sends and CAN receives:

cd
cd RS485_CAN_HAT_Code/RS485_TO_CAN/wiringPi/
make clean
make
sudo ./485_send

Python Example

If you have already downloaded, please skip the file deletion step and the program download step (the two steps below).
Delete the previously downloaded package.

Please note: If you want to keep the original RS485_CAN_HAT_Code file, please copy it to another path.

cd
rm -rf RS485_CAN_HAT_Code.zip
rm -rf RS232-485-422_Code.zip
rm -rf RS485_CAN_HAT_Code
sudo ifconfig can0 down

Download the demo:

cd
sudo apt-get install unzip
wget https://files.waveshare.com/wiki/RS232-485-422-TO-CAN/RS232-485-422_Code.zip
unzip RS232-485-422_Code.zip
sudo chmod 777 -R RS485_CAN_HAT_Code/

Reopen the can0, CAN sends and RS485 receives:

cd
cd RS485_CAN_HAT_Code/CAN_TO_RS485/python/
sudo python can_send.py

Reopen the can0, RS485 sends and CAN receives:

cd
cd RS485_CAN_HAT_Code/RS485_TO_CAN/python/
sudo python 485_send.py

Resource

Software

External Test Demo

RS485 CAN HAT Demo

Datasheet

FAQ

Question:The configurations are all correct, but the communication is not working?

Answer:

Please press and hold the reset button for more than 5 seconds until the indicator blinks continuously (factory restored), and then reconfigure the communication parameters as required.

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Question:Why does the CAN ID only receive two bytes?

Answer:

Please note that the received data frame type. If the received data type is an extended frame, the frame ID is 0xFFFFFFFF & CAN_ID. If the received data type is a standard frame, the frame ID is 0x000007FF & CAN_ID, which is not related to the frame type configured by the software (in transparent conversion mode).
Use the one configured by the software as the frame type when sending data, as follows:

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Question:Does the module has onboard 120ohm resistor?

Answer:

Yes, if you want to modify the 120R, you can move the jumper cap on the RS485/422 terminal to the 120R.

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Question:What can I do if the remote communication of the RS485/422 is abnormal?

Answer:

You can move the jumper cap of the RS485/422 to the 120R.

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Question:How to deal with RS485/422 short-distance communication anomalies, where extra 0s or garbled data are received?

Answer:

Do not enable the two 120Ω termination matching resistors of RS485/422, i.e., the jumper cap should be set to NC.

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