Modbus TCP on Raspberry Pi to Ignition


I would like to know if there are any visible issues with my code here as I have been trying to read the values off of the modbusTCP server and I have had no success. The status of my modbus server on ignition is connected, but whenever I try to read values from the server it just returns 0. I have tried reading ir1 when I have to code like this, I have had the code write to 30001, and tried reading both ir1 then and ir30001. I may try writing to 1 using databank.setwords() and then using coil to read the values, but I'm pretty sure that its going to read 0 anyway. (Update: coil didn't work either)

Currently my code is outputting the correct values in terminal (its a raspberry pi), and its also outputting sent, so I'm no sure exactly where the issue is arising. I have also tried converting to 16 bit integers but I still had the same issue.

This code is python running on an raspberry pi 3 model b.

#!/usr/bin/env python3
import time
import os
import Adafruit_ADS1x15
import struct
from pyModbusTCP.server import ModbusServer, DataBank

# Initialize ADS1115 ADC
adc = Adafruit_ADS1x15.ADS1115()

# Set up GPIO pins

# ADS1115 pins
ADS_SCL_PIN = 3  # SCL pin on ADS1115
ADS_SDA_PIN = 2  # SDA pin on ADS1115

# Modbus TCP server details
server = ModbusServer("", 502, no_block=True)  # Replace with your desired IP address and port

def sensor():
    for i in os.listdir('/sys/bus/w1/devices'):
        if i.startswith('28-'):
            ds18b20 = i
            return ds18b20

def read_temp_raw(sensor_id):
    sensor_path = '/sys/bus/w1/devices/{}/w1_slave'.format(sensor_id)
    f = open(sensor_path, 'r')
    lines = f.readlines()
    return lines

def read_temp(sensor_id):
    lines = read_temp_raw(sensor_id)
    while lines[0].strip()[-3:] != 'YES':
        lines = read_temp_raw(sensor_id)
    equals_pos = lines[1].find('t=')
    if equals_pos != -1:
        temp_string = lines[1][equals_pos + 2:]
        temp_c = float(temp_string) / 1000.0
        temp_f = temp_c * 9.0 / 5.0 + 32.0
        return temp_c, temp_f

    sensor_id = sensor()
    print("server start")

    while True:
        # Read temperature
        temp_c, temp_f = read_temp(sensor_id)

        # Convert temperature values to 16-bit signed integers

        # Read water level from ADS1115
        adc.start_adc(0, gain=1)
        time.sleep(0.1)  # Add a small delay for the conversion to complete
        water_level_value = adc.get_last_result()

        # Convert water level value to 16-bit signed integer

        print("Temperature Sensor Value: {:.2f}°C, {:.2f}°F".format(temp_c, temp_f))
        print("Water Level Sensor Value: {}".format(water_level_value))

        # Write temperature and water level values to Modbus input registers
        server.data_bank.set_input_registers(1, [int(temp_c)])  # Input Register 30001 for temperature
        server.data_bank.set_input_registers(2, [int(temp_f)])  # Input Register 30002 for temperature
        server.data_bank.set_input_registers(3, [int(water_level_value)])
        time.sleep(0.5)  # Add a delay of 0.5 seconds after setting values

        # Check if all values are set properly
        if (server.data_bank.get_input_registers(1)[0] == int(temp_c) and
            server.data_bank.get_input_registers(2)[0] == int(temp_f) and
            server.data_bank.get_input_registers(3)[0] == int(water_level_value)):

except KeyboardInterrupt:
    # Stop the Modbus server
    print("server stop")

Are you off by 1 address? Trying turning on "Zero-based Addressing" in the Ignition device settings.


You are a hero, and I should have noticed this earlier.