RS485 RS232 HAT

Instruction

Product Description

RS485 RS232 HAT is an isolated RS485 and RS232 expansion board specially designed by Waveshare for Raspberry Pi. It adopts SC16IS752+SP3485, SP3232 scheme, built-in power isolation, ADI magnetic coupling isolation and TVS and other protection circuits.

Feature

Based on Raspberry Pi 40pin GPIO interface, suitable for Raspberry Pi series boards.
Using SC16IS752 and SP3485, SP3232 multi-chip combination scheme, can realize SPI to RS485, RS232, the communication rate is up to 921600bps.
RS485 supports manual or automatic sending and receiving of data, which can be set by DIP switch.
RS485 onboard resettable fuse and protection diode can ensure stable output of current and voltage, prevent overcurrent and overvoltage, and improve shock resistance.
Onboard TVS (transient voltage suppression tube), which can effectively suppress the surge voltage and transient peak voltage in the circuit, and protect against lightning and static electricity.
Onboard power supply and serial port transceiver indicators, easy to check the module power supply and communication status.
Lead out the SPI control interface for easy access to main control boards such as Arduino.
Provide complete supporting information manuals (C and python sample programs and user manuals, etc.).

Product parameters

Serial port expansion chip: SC16IS752
RS485 transceiver： SP3485
RS232 transceiver： SP3232
Communication Interface： SPI
Communication rate： 300~921600 bps
Operating Voltage： 3.3/5V
Dimension： 65mm × 56.5mm
Via diameter： 3.0mm

Interface Description

Pin function

Pin Number	Identification	Pin Description
1	VCC	3.3V/5V Power
2	GND	GND
3	SCLK	SPI clock input
4	MOSI	SPI data input
5	MISO	SPI data output
6	CS	SPI Chip select signal
7	IRQ	interrupt output
8	EN	RS485 output enable

Hardware Description

Controller

This product uses SC16IS752 as the control chip. SC16IS752 is a dual-channel high-performance UART expansion chip that supports SPI and I2C interface communication. This module uses the SPI interface. Onboard power isolation, ADI magnetic coupling isolation, onboard TVS (transient voltage suppression tube), self-recovery fuse and protection diode and automatic transceiver conversion circuit. It can effectively suppress the surge voltage and transient peak voltage in the circuit, prevent lightning and static electricity, prevent overcurrent and overvoltage, improve the anti-shock ability, and can carry out signal isolation. It has the advantages of high reliability, strong anti-interference, and low power consumption.

Letter of Agreement

CS: the slave chip selection, when CS is low level, the chip is enabled.
SCLK: SPI communication clock.
MOSI/SI: SPI communication host sends, the slave receives.
MIS0/SO: SPI communication host receives, the slave sends.
Timing: CPHL=0, CPOL=0 (SPI0)
[Remarks] For specific information about SPI communication, you can search for information online.

Hardware connection

Detailed connection:
The C and python demos need an additional RS485 to serial port module connected to channel 1 to see the effect. test.py in Python requires channel 1 and channel 2 to be connected.

Function Pins	Raspberry Pi Interface (BCM)	Description
VCC	5V	3.3V/5V power supply positive
GND	GND	Power Ground
SCLK	D21(SPI1 SCLK)	SPI clock input
MOSI	D20(SPI1 MOSI)	SPI data input
MISO	D19(SPI1 MISO)	SPI data output
CS	D18(SPI1 CS)	SPI Chip Select Signal
IRQ	D24	Interrupt output, can be switched to D16, D12, D25 pins
EN	D22	RS485 TX/RX enable: high level for TX, low level for RX

Add driver

Execute in terminal:

sudo nano /boot/config.txt
#Add the following, int_pin is set according to the actual welding method:
dtoverlay=sc16is752-spi1,int_pin=24
#reboot device
sudo reboot

After restarting, the driver of SC16IS752 will be loaded into the system kernel. At this time, you can run ls /dev to check the following devices:

In the Raspberry Pi system on 2020-05-27, gpiochip3 has not become gpiochip2

Install the library

PS: If you are using the system of the Bullseye branch, you need to change "apt-get" to "apt", the system of the Bullseye branch only supports Python3, and there is no wiringPi.

Install BCM:

wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.71.tar.gz
tar zxvf bcm2835-1.71.tar.gz
cd bcm2835-1.71/
sudo ./configure && sudo make && sudo make check && sudo make install
# For more information, please refer to the official website: http://www.airspayce.com/mikem/bcm2835/

Install wiringPi:

sudo apt-get install wiringpi
#For Raspberry Pi 4B may need to be upgraded;
cd /tmp
wget https://project-downloads.drogon.net/wiringpi-latest.deb
sudo dpkg -i wiringpi-latest.deb
gpio -v
# Run gpio -v and version 2.52 will appear. If it does not appear, the installation is wrong

Install python2 library:

sudo apt-get update
sudo apt-get install python-pip
sudo pip install RPi.GPIO
sudo apt-get install python-serial

Install python3 library:

sudo apt-get update
sudo apt-get install python3-pip
sudo pip3 install RPi.GPIO
sudo apt-get install python3-serial

Testing

Download and run the test demo:

sudo apt-get install p7zip-full
wget https://files.waveshare.com/upload/4/44/RS485_RS232_HAT.zip
7z x RS485_RS232_HAT.zip
sudo chmod 777 -R  RS485_RS232_HAT
cd RS485_RS232_HAT/

C demo:

cd c
make clean
make
sudo ./main

PYTHON demo:

cd python
cd examples
#Use RS485 for communication
sudo python3 RS485.py
#Use RS232 for communication
sudo python3 RS232.py
#Use RS232 TO RS485 to make the modules communicate with each other
sudo python3 test.py

Resourse

Document

Schematic

Demo

Sample Demo

Datasheet

FAQ

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

Answer:

Determine whether A and B of 485 correspond to the controlled 485 devices one by one;
You can use the USB to 485 device to communicate with the module first to ensure that there is no problem with the settings of the Raspberry Pi;
Check the setting of odd and even bit parity of serial communication parameters.

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