2-CH RS485 HAT
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Introduction
This is a dual-channel isolated RS485 extension board specially designed for raspberry PI, which adopts SC16IS752+SP3485 solution, embed with protection circuits such as power supply isolation, ADI magnetical isolation, and TVS diode, etc. It is easy to control the 2-channel RS485 for auto transceiving via SPI interface. Due to its fast communication, stability, reliability, and safety, it is an ideal choice for fields like industrial automation.
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Interfaces
VCC | 3.3V |
PIN | Description |
VCC | 3.3V/5V Power |
GND | Ground |
SCLK | SPI Clock input |
MOSI | SPI Data input |
MISO | SPI Data output |
CS | SPI Chip Selection |
IRQ | Interrupt output (Interrupt Request) |
EN1 | Channel 1 output enable |
EN2 | Channel 2 output enable |
Working principle
Introduction
This product adopts SC16IS752 as controller. SC16IS752 is a dual-channel high-performance UART expansion chip that supports SPI and I2C interfaces communication. This module uses SPI interface. Onboard power isolation, ADI magnetic coupler isolation, onboard TVS (transient voltage suppression tube), self-recovery fuses, protection diodes and automatic transceiver switching circuit. It can effectively suppress the surge voltage and transient peak voltage in the circuit, prevent lightning and static electricity, prevent over voltage, improve the anti-impact ability, can conduct signal isolation, with high dependence, strong anti-interference, low power consumption advantages, etc.
Communication protocol
- CS:Slave chip selection, when CS is low, the slave chip is enabled.
- SCLK:SPI communication clock
- MOSI/SI:SPI Communication master sends, slave receives
- MOSI/SI:SPI Communication master receives, slave sends
- Timing Sequence:CPHL=0, CPOL=0 (SPI0)
Raspberry Pi
We provide C and Python demo codes. A quick testing example is provided in python.
- Detailed Connection
To run examples, you should prepare an external RS485 to UART module, connect it to Channel 1 of 2-CH RS485 HAT. When you test the test.py, you need to wire Channel 1 and Channel 2 of 2-CH RS485 HAT.
485 PIN | Raspberry Pi(BCM) |
VCC | 5V |
GND | GND |
SCK | P21 (SPI1 SCLK) |
MOSI | P20 (SPI1 MOSI) |
MISO | P19 (SPI1 MISO) |
CS | P18 (SPI1 CS) |
IRQ | P24 |
EN1 | P27 |
EN2 | P22 |
- Software setup
- Open the terminal and modify config.txt file by commands:
sudo nano /boot/config.txt
- Add the following, int_pin is set according to the actual welding mode:
dtoverlay=sc16is752-spi1,int_pin=24
sudo reboot
- After rebooting, the driver of SC16IS752 will be loaded into the system kernel. You can run ls /dev to check the following devices:
- Install Libraries
- Install wiringpi
sudo apt-get install wiringpi # An upgrade may be required for raspberry PI 4B: cd /tmp wget https://project-downloads.drogon.net/wiringpi-latest.deb sudo dpkg -i wiringpi-latest.deb gpio -v # Running gpio-v to check if the version is 2.52, If it is not, you need to check the installation again.
- Install the python2 library
sudo apt-get update sudo apt-get install python-pip sudo pip install RPi.GPIO sudo apt-get install python-serial
- Install the python3 library
sudo apt-get update sudo apt-get install python3-pip sudo pip3 install RPi.GPIO sudo apt-get install python3-serial
- Install the python3 library
sudo apt-get update sudo apt-get install python3-pip sudo pip3 install RPi.GPIO sudo apt-get install python3-serial
- Test
- Download and run the examples:
sudo apt-get install p7zip-full wget http://www.waveshare.net/w/upload/4/44/2-CH_RS485_HAT_code.7z 7z x 2-CH_RS485_HAT_code.7z sudo chmod 777 -R 2-CH_RS485_HAT cd 2-CH_RS485_HAT/
- You can also download the project on our Github:
sudo git clone https://github.com/waveshare/2-CH-RS485-HAT cd 2-CH-RS485-HAT/
- C program
cd c make clean make sudo ./main
- Python program
cd python cd examples sudo python main.py
The demonstration here is: Channel 1 of the 2-CH RS485 HAT is connected to the USB TO RS232/485/TTL. As follows:
Connect USB TO RS232/485/TTL to the computer, open the serial port assistant, select the corresponding serial port, and set the baud rate to 115200.
- Run the C program,the data sent by computer will all be received by Raspberry Pi,as showned below:
Note: The path of the samples is based on the actual directory;
- Run the main.py of Python program,the data sent by computer will all be received by Raspberry Pi,as showned below:
Note: The path of the samples is based on the actual directory;
If there is no other RS485 devices, you can choose the test method as follow to connect channel 1 with channel 2:
- Running result of test.py :
Documentation
Demo code
Datasheets
FAQ
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2). Determine whether A and B of 485 correspond one-to-one with the controlled 485 devices A and B;
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