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3.2 Serial port Operation of Pyserial
Python has its own dedicated Serial library. It is not clear whether the serial port library of pyqt inherits this library without carefully reading the code of qt.
Tell me why I suddenly switched to this library, because the upper computer and the lower computer plan to use ModBus as the communication protocol. I thought that PyQt is a complete inheritance of all classes of C++ Qt, but it doesn’t work, it’s not the case. All the classes starting with QModbus are not found in the pyqt documentation. So it seems not easy to do all the host computer functions with PyQt. After searching, I found that Python has a Modbus_tk library, which encapsulates the related functions of Modbus, including rtu, ascii protocol mode, master and slave node mode. And this library directly inherits the Pyserial library. OK In this case, it will be simpler and more efficient to use the pyserial library directly for the operation of the serial port.
Pyserial official document address https://pythonhosted.org/pyserial/
3.2.1 List available serial ports
import serial.tools.list_ports # The corresponding function is under this package. Import serial directly cannot use this toolkit
com_list = serial.tools.list_ports.comports() # Return a serial.tools.list_ports.ListPortInfo list object, Each element contains multiple attributes of the serial port
for port in com_list:
print(port.device) #Return the port number such as COM3
print port.describe) #Return the device name
print(port.location) #Return the location of the device on the computer
After obtaining these more important information You can open the port
3.2.2 Open the serial port
import serial
ser = serial.Serial(com_list[0].device, baudrate=19200, bytesize=EIGHTBITS, parity=PARITY_NONE, stopbits=STOPBITS_ONE, timeout=None, xonxoff=False) #Create a Serial instance object by directly configuring the parameters, and then directly open the port after execution
ser = serial.Serial()
ser.baudrate=19200
ser.port=com_list[0].device
open() #This method can be configured first and then opened
ser.close()
3.2.3 Abnormal state judgment of serial port
Before using the QSerialPort() class, there is an error() method to judge the status of the serial port. But PySerial does not seem to have such complete functions. I don’t have enough ability to realize this function. Here is a method that I want to have basic functions.
After the serial port is opened normally, even if the device is unplugged, use ser.is_open to determine that the serial port status is always True. But by obtaining the serial port information, an empty object is obtained. Based on this idea, rewrite the code that opens the serial port and sends data through the serial port.
>
4. Communication part
This part mainly realizes the communication between the upper computer software and the lower computer.
4.1 host computer modbus master
The modbus implementation of the host computer adopts python’s existing modbus_tk library to realize, paste the basic code
< div> PORT =’COM3′
4.2 The lower computer modbus part is based on Arduino
uses arduino The modbus library, which sets a register with an address of 4.
/**
* Modbus slave example 2:
* The purpose of this example is to link the Arduino digital and analog
* pins to an external device.
*
* Recommended Modbus Master: QModbus
* http://qmodbus.sourceforge.net/
*
* Editado al espa?ol por LuxARTS
*/
//Incluye la librería del protocolo Modbus
#include
#include
#define ID 1
/ /Crear instancia
Modbus slave(ID, 0, 0); //ID del nodo. 0 para el master, 1-247 para esclavo
//Puerto serie (0 = TX: 1-RX: 0)
//Protocolo serie. 0 para RS-232 + USB (default), cualquier pin mayor a 1 para RS-485
boolean led;
int8_t state = 0;
unsigned long tempus;< /p>
uint16_t au16data[9]; //La tabla de registros que se desea compartir por la red
/***************** ****************************************
Configuración del programa
* ************************************************** ******/
void setup() {
io_setup(); //configura las entradas y salidas
slave.begin(19200); //Abre la comunicación como esclavo
tempus = millis() + 100; //Guarda el tiempo actual + 100ms
digitalWrite(13 , HIGH ); //Prende el led del pin 13 (el de la placa)
au16data[4] = 0x8000;
}
/********** ***********************************************
Inicio del programa
************************************************ *************/
void loop() {
//Comprueba el buffer de entrada
state = slave.poll( au16data, 9 ); //Parámetros: Tabla de registros para el intercambio de info
// Tama?o de la tabla de registros
//Devuelve 0 si no hay pedido de datos
//Devuelve 1 al 4 si hubo error de comunicación
//Devuelve mas de 4 si se procesó correctamente el pedido
if (state> 4) {//Si es mayor a 4 = el pedido fué correcto
tempus = millis() + 50; //Tiempo actual + 50ms
digitalWrite(13, HIGH);//Prende el led
}
if (millis()> tempus) digitalWrite(13, LOW );//Apaga el led 50ms despu és
//Actualiza los pines de Arduino con la tabla de Modbus
io_poll();
}
/**
* pin maping :
* 2-digital input
* 3-digital input
* 4-digital input
* 5-digital input
* 6-digital output
* 7-digital output< br> * 8-digital output
* 9-digital output
* 10-analog output
* 11-analog output
* 14-analog input
* 15-analog input
*
* pin 13 reservado para ver el estado de la comunicación
*/
void io_setup() {
pinMode(2, INPUT);
pinMode(3, INPUT);
pinMode(4, INPUT);
pinMode(5, INPUT);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
pinMode(10, OUTPUT);
pinMode(11, OUTPUT);
pinMode(13, OUTPUT);
digitalWrite(6, LOW );
digitalWrite(7, LOW );
digitalWrite(8, LOW );
digitalWrite(9, LOW );
digitalWrite(13, HIGH ); //Led del pin 13 de la placa
analogWrite(10, 0 ); //PWM 0%
analogWrite(11, 0 ); //PWM 0%
}
/**************************** *****************************
Enlaza la tabla de registros con los pines
******* ************************************************** /
void io_poll() {
long temp;
// digital inputs -> au16data[0]
// Lee las entradas digitales y las guarda en bits de la primera variable del vector
// (es lo mismo que hacer una máscara)
bitWrite( au16data[0], 0, digitalRead( 2 )); //Lee el pin 2 de Arduino y lo guarda en el bit 0 de la variable au16data[ 0]
bitWrite( au16data[0], 1, digitalRead( 3 ));
bitWrite( au16data[0], 2, digitalRead( 4 ));
bitWrite( au16data[0], 3, digitalRead( 5 ));
// digital outputs -> au16data[1]
// Lee los bits de la segunda variable y los pone en las salidas digitales
digitalWrite( 6, bitRead (au16data[1], 0 )); //Lee el bit 0 de la variable au16data[1] y lo pone en el pin 6 de Arduino
digitalWrite( 7, bitRead( au16data[1], 1 ));
digitalWrite( 8, bitRead( au1 6data[1], 2 ));
digitalWrite( 9, bitRead( au16data[1], 3 ));
// Cambia el valor del PWM
analogWrite( 10, au16data[ 2] ); //El valor de au16data[2] se escribe en la salida de PWM del pin 10 de Arduino. (siendo 0=0% y 255=100%)
analogWrite( 11, au16data[3]) ;
temp=au16data[4];
// Serial.write(temp>>16);
// Serial.write(temp>>8);
// Serial.write(temp);
// Lee las entradas analógicas (ADC)
temp=(long)temp+(long)(random(-3,4)) ;
//temp=-1;
// Serial.write(temp>>24);
// Serial.write(temp>>16);
// Serial.write( temp>>8);
// Serial.write(temp);
temp=temp<0?0:temp;
temp=temp>65535?65535:temp ;
//temp=temp<0?0:temp;
//temp=temp>65535?65535:temp;
au16data[4] = temp;
//au16data[4] = byte(random(65530,65535));//analogRead( 0 ); //El valor anaalógico leido en el pin A0 se guarda en au16data[4]. (siendo 0=0v y 1023 =5v)
au16data[5] = 0xffff;
// Diagnóstico de la comunicación (par a debug)
au16data[6] = slave.getInCnt(); //Devuelve cuantos mensajes se recibieron
au16data[7] = slave.getOutCnt(); //Devuelve cuantos mensajes se transmitieron
au16data[ 8] = slave.getErrCnt(); //Devuelve cuantos errores hubieron
}
#So far the basic framework has been built, The communication between the upper computer and the lower computer is also opened up. The hardware problem has been basically solved
I started to focus on GUI writing.
Author: geokai
Source: https://www.cnblogs.com/geokai/
< p>The copyright of this article belongs to the author geokai and blog garden. Reprinting and commercial use are welcome, but this statement must be retained without the author’s consent, and the original link must be given in an obvious place on the article page, otherwise the right to pursue legal responsibility is reserved.
If you have any questions, please email ([email protected]) for consultation.
div
ser =serial.Serial()
> ser.baudrate=19200
ser.port=’COM3′
ser.timeout=1
try:
print(‘Opened’)
except serial.SerialException:
print(‘error’)
p>
time.sleep(5) #Pause, unplug the serial device
if ser.is_open and len(list(lp.grep(ser.port) )) !=0: #
print(‘able to send’)
for i in range(3):
try:
aaaaaaaaaaaaa .
print(‘send ok’)
serial serial lException:
print ( ‘re-try’)
ser.close ()
ser.open ()
if i ==2:
ser.close()
close close(‘port error’) : )
print(‘port error’)
import modbus_tk
import modbus_tk.defines as cst
import serial
from modbus_tk import modbus_rtu
import time
PORT =’COM3′
def main(master):
try:
#Connect to the slave
master.set_timeout(1)
master.set_verbose(True)
x = master.execute (1, cst.READ_INPUT_REGISTERS, 4,1) #Read the register value of the lower computer, the address is 4, and the length is 1, using cst.READ_INPUT_REGISTERS and cst.READ_HOLDING_REGISTERS The effect is the same
if len(x)>0:
print(x[0]) #here is the value obtained, pay attention to the sign, in this example the lower computer also uses 16-bit unsigned numbers
except :
print(‘unknown’ error)
if __name__ == “__main__”:
master = modbus_rtu. RtuMaster(
serial.Serial( port=PORT, baudrate=19200, bytesize=8, parity=’N’, stopbits=1, xonxoff=0))
while True:
main(master)
tme.sleep(1)
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