Modbus with temperature/humidity/gas sensor .

[Nestor973]

Hi,

i have to say i’m pretty new to the modbus protocol. I Have a Controllino Maxi that should communicatie with this sensor :

https://www.goveco.com/en/products/sensing/368809/odvcm-multifunctional-sensor

According to the LED’s on the sensor, it should be powered OK. I did supply it with 24vDC+ and i split the ground to the main ground and the ground of the RS485 port (not sure if that is ok, but i think so?)

Anyhow, i tried the ModbusMaster demo in the arduino IDE and it gives me nothing. The device slave address is 1 as stated in the PDF.

I think the demo code should at least be able to read something from the sensor?

Thanks in advance for any input on this.

[Nestor973]

#include <Controllino.h>
#include “ModbusRtu.h”
#define MasterModbusAdd 0
#define SlaveModbusAdd 1
#define RS485Serial 3

String result;
uint16_t au16data[16];
uint8_t u8state;

Modbus master(SlaveModbusAdd, RS485Serial, 0);

modbus_t telegram;

unsigned long u32wait;

void setup() {

Serial.begin(9600);
while (!Serial){}
Serial.println(“Connecting to Serial3 “);
master.begin(19200);
master.setTimeOut(5000); // if there is no answer in 5000 ms, roll over
u32wait = millis() + 2000;
u8state = 0;
telegram.u8id = 1; // slave address
telegram.u8fct = 4; // function code (this one is registers read)
telegram.u16RegAdd = 1; // start address in slave
telegram.u16CoilsNo = 1; // number of elements (coils or registers) to read
telegram.au16reg = au16data; // pointer to a memory array in the Arduino

}

void loop() {

switch( u8state ) {

case 0:

if (millis() > u32wait) u8state++; // wait state

break;

case 1:

master.query(telegram); // send query (only once)
u8state++;
break;

case 2:

master.poll(); // check incoming messages
if (master.getState() == COM_IDLE) {
u8state = 0;
u32wait = millis() + 1000;
Serial.print(“ontvangen data: “);
Serial.println(au16data[0]);

}

break;

}

delay(200);

}

• This reply was modified 3 years, 1 month ago by  Nestor973.
• This reply was modified 3 years, 1 month ago by  Nestor973.
• This reply was modified 3 years, 1 month ago by  Nestor973.

[Nestor973]

This is what i’ve come up with so far. I have no idea but i think this should result something.
What i don’t know if is my sensor is correctly wired. I did order a USB-RS485 dongle to check if it really
works at all. Hope someone can confirm if the code below should come up with a result.

The address of the sensor is 1 , that’s for sure, the input register for temperature is also 1, so..

[Nestor973]

The problem was in the Parity , i set it to
master.begin(19200,SERIAL_8E1);

and now i get data out of the sensor. Data is still a bit weird (about 50°C where it should read 20 or so),but that’s another issue that has nothing to do with controllino.

[Lukas]

Hi,

thanks for sharing! Have you also resolved the issue with the wrong temperature?

Lukas