RS485 CAN HAT

RS485 CAN HAT Raspberry Pi small size and low cost RS485 CAN expansion board RS485 CAN HAT for Raspberry Pi

RS485 CAN HAT (B) Raspberry Pi Isolated RS485 CAN Expansion Board

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Onboard Interfaces RS485 CAN

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Introduction

The RS485 CAN HAT will enables your Pi to communicate with other devices stably in long-distance via RS485/CAN functions.

More

Note:

There are two versions. The only difference betweem these version are the crystal. The old one use 8M and the line added to config.txt file should be:

dtoverlay=mcp2515-can0,oscillator=8000000,interrupt=25,spimaxfrequency=1000000

The new one use 12M crystal and the line should be

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

Resources

Documents

• User Manual
• Schematic

Demo code

• Demo code

Datasheet

• MCP2515
• SN65HVD230
• SP3481_SP3485

3D Drawing

• 3D Drawing

FAQ

Question: Imprint?

 Answer:

• The current version is 12M, you can view the front of the module:
  

Then the corresponding command in config.txt is:

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

• If you have an old version, there should be an 8M crystal oscillator, as shown below:
  

Then the corresponding command in config.txt is:

dtoverlay=mcp2515-can0,oscillator=8000000,interrupt=25,spimaxfrequency=1000000

Question:Why can't I control the module with UART on Raspberry Pi, can't open ttyS0 through minicom, prompting any ttyS0?

 Answer:

Open the Raspberry Pi terminal and enter the following command to access the configuration screen:

sudo raspi-config
Select Interfacing Options -> Serial to turn off shell access and turn on the hardware serial port

Raspberry Pi 2B/zero, the user serial device number is ttyAMA0; you can use the following command line to confirm that serial0 is the selected serial device number, as follows:

ls -l /dev/serial*

• For Raspberry Pi 3B/2B/Zero, the serial port is typically used for Bluetooth. When you comment out this setting, it defaults to S0. However, Raspberry Pi 4 does not have this statement by default.

#dtoverlay=pi3-miniuart-bt

And then reboot the Raspberry Pi:

sudo reboot

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Question:Can't send and receive data?

 Answer:

1. Make sure the baud rates on both sides are the same;
2. The fixed frame ID is set in the demo: 0X123, please set the sending and receiving CAN ID of the other end of your CAN to be x0123;

Question:With or without isolation?

 Answer:

This is an entry-level 485 and CAN, both without isolation.

Question:485 Communication is abnormal, what should I do?

 Answer:

1. Determine the hardware version of the Raspberry Pi, if it is the Raspberry Pi ZERO/3B, the serial port in the program needs to be modified to /dev/ttyAMA0;
2. Check whether the serial communication of the Raspberry Pi has enabled flow control;
3. Determine whether A and B of 485 correspond to the controlled 485 devices A and B one by one;
4. You can use the USB to 485 devices to communicate with the RS485 CAN HAT first to ensure that there is no problem with the settings of the Raspberry Pi;
5. Check the setting of odd and even bit parity of serial communication parameters.

Question:How to configure the config.txt file when the Ubuntu system is installed on the Raspberry Pi?

 Answer:

1. Mainstream Ubuntu system config.txt files are usually in the /boot/firmware folder
2. Or use the SD card of the Raspberry Pi to read and change the config.txt file under the computer (or other hosts that can recognize the SD card) through the card reader.

Question:After connecting the sensor to RS485, the corresponding program does not receive data?

 Answer:

The sensor may send hex data (sometimes it is necessary to send hex data to the sensor to request data), follow the steps below to send and receive hex data:

wget https://files.waveshare.com/upload/0/00/RS485-CAN-HAT-For-Hex.zip
unzip RS485-CAN-HAT-For-Hex.zip
sudo chmod 777 RS485-CAN-HAT-For-Hex.zip
cd RS485-CAN-HAT-For-Hex
#Receive Hex
sudo python3 RS485-CAN-HAT-send-hex.py
#Send Hex
sudo python3 RS485-CAN-HAT-receive-hex\.py

Question:CAN communication will get slower and slower, the back can only often re-can port, sometimes indeed the speed of the program is quite slow?

 Answer:

If it means that the output part of data processing becomes slower, it should help to improve the performance of the upper computer; you can also consider clearing the cache before each read to read only the latest data for processing.

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Question:Do I need to connect GND for RS485 communication?

 Answer:

Can be used without connecting to the GND, connected to the GND signal may be more stable, connected to GND to obtain better performance, reliability, and anti-interference ability, and long-distance communication. Hence, it is recommended to connect the GND.

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Question:If the installation of Python libraries fails on the latest Raspberry Pi system, what should you do?

 Answer:

After entering "myenv", you can install the corresponding Python library again. In the "myenv" environment, all commands are executed without "sudo".

sudo apt install python3-venv
python3 -m venv myenv &&source myenv/bin/activate
source myenv/bin/activate
pip install requests

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Question:Why is the external USB-CAN box communication abnormal?

 Answer:

• The CAN rate of the host and the slave should be the same.
• Both ends of the 120 ohm balancing resistors are turned on.
• The frame ID of the transmitter should correspond to the filter ID of the receiver.

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Support

If you require technical support, please go to the Support page and open a ticket.