Template:WSSP08A Pi Guides

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We use 2-CH RS485 HAT(should purchase separately) and Raspberry Pi for testing. For more information about how to use the 2-CH RS485 HAT, you can refer to 2-CH RS485 HAT

Hardware connection

Hesman Connector
1 V+(12V~36V)
2 A(Change 2)
3 V-(GND)
4(Gnd.png) B(Change 2)


PIN Raspberry Pi(BCM) Description
VCC 5V 3.3V/5V
GND GND GND
SCLK P21(SPI1 SCLK) SPI clock input
MOSI P20(SPI1 MOSI) SPI Data input
MISO P19(SPI1 MISO) SPI Data Output
CS P18(SPI1 CS) SPI chip selection
IRQ P24 Inttrupt pin
EN1 P27 Channel 1(Channel 1) enable pin: High: Send enable; Low: Receive enable
EN2 P22 Channel 2(Channel 2) enable pin: High: Send enable; Low: Receive enable

Install Driver

  • Open a terminal and run the commands:
sudo nano /boot/config.txt
#Add the following lines to file. Note that the ini_pin should be same as the actual define.
dtoverlay=sc16is752-spi1,int_pin=24
#Reboot
sudo reboot

After reboot, The SC16IS752 drive is installed in kernel, you can check the device by command ls /dev:
2-CH-RS485-HAT-3.png
If the kernel version is 5.4 or obove, the gpiochip3 is recognized as gpiochip2

Install Libraries

  • Install wiringPi
sudo apt-get install wiringpi
cd /tmp
wget https://project-downloads.drogon.net/wiringpi-latest.deb
sudo dpkg -i wiringpi-latest.deb
gpio -v
# Check if it is 2.52 version
  • Install python2 libraries
sudo apt-get update
sudo apt-get install python-pip
sudo pip install RPi.GPIO
sudo apt-get install python-serial
sudo apt-get install python-crcmod
  • Install python3 libraries
sudo apt-get update
sudo apt-get install python3-pip
sudo pip3 install RPi.GPIO
sudo apt-get install python3-serial
sudo apt-get install python3-crcmod

Testing

  • Download and run the demo codes
sudo apt-get install p7zip-full
sudo wget https://www.waveshare.com/w/upload/1/1a/WSSP08A_Code.7z
sudo 7z x WSSP08A_Code.7z
sudo chmod 777 -R WSSP08A_Code
cd WSSP08A_Code/
  • C example
cd c
make clean
make
sudo ./main
  • python example
#python2
cd python 
cd examples
sudo python main.py
#python3
cd python 
cd examples
sudo python3 main.py

About the Codes

  1. The demo codes are made for a situation that only one sensor is connected, it will read data according to the device address and it can be used to modify the device address.

WSSP08A run.png

  • C codes
#Read the device address (only one device is connected to RS485 bus)
uint8_t WSSP08A_get_addr(void)
#Modify the address of target device
uint8_t WSSP08A_set_addr(uint8_t o_addr, uint8_t n_addr)
#Read the data from target device
float WSSP08A_get_pressure(uint8_t addr)
  • python codes
#Get 16CRC result
def crc16Add(self,read):
#Read the device address (only one device is connected to RS485 bus)
def get_addr(self):
#Read the data from target device
def get_press(self,addr):
#Modify the address of target device
def set_addr(self,o_addr,s_addr):