Arduino RS485 and I2C at same time

Projects Networking, Protocols, and Devices
1

Hi,

I have Arduino NANO connected with Domat MarkMMX PLC through the RS485 ( TX1, RX0 ). For data / register reading is in the PLC used Modbus RTU protocol. Is working OK. But when I connect light sensor ( with I2C communication ) and change the code to read value, Modbus RS485 communication hang up that time.

Could someone help me? Thank you.

Problem solved!!! No attention necessary.

2

If you were to provide a drawing of how you have wired up the various component parts to your Nano, and share your whole sketch - or a simpler sketch that demonstrates the problem, then you will have a better chance of getting a helpful reply.

EDIT: And please don't make duplicate posts.

3

Light sensor BH1750 connected to A4 &A5. TTL to RS485 converter connected as TX1 - DI, RX0 - RO, DE,RE - D4.

Shortened code:

#include <BH1750.h>
#include<ModbusRtu.h>
#include <Wire.h>

BH1750 lightMeter;

float lux;

Modbus bus;  

uint16_t modbus_array[] = {180,20,40};

void setup()
{
  Wire.begin();
  bus = Modbus(10,1,4);
  bus.begin(19200);
}

void loop()
{
   lux = lightMeter.readLightLevel();

   bus.poll(modbus_array,sizeof(modbus_array)/sizeof(modbus_array[0]));
   modbus_array[2] = lux;

  if (modbus_array[0] == 300)   
  {
    digitalWrite(led1,LOW);
  }
  else   
  {
    digitalWrite(led1,HIGH);
  }
}

Problem with RS485 hanging happens when I put the code for sensor value reading.
lux = lightMeter.readLightLevel();

4

@miluk,
I have deleted your other topic on the same subject, please post your questions once only.

Thank you.

5

OK. Thanks. Using forum for first time.... Sorry. Best regards.

6

What type of Arduino are you using? I cannot find a board that has I2C on A4/A5 but also has TX1 and RX0.

BTW, connecting the RS485 TX and RX to different serial ports is a very bad idea. Post a wiring diagram!

That connects Modbus to Serial1. As you connected the reception of the RS485 to RX0 you won't see any replies.