Trying to increment a Holding Register every time what the Master reads an expecific Holding Register...

[WagnerDeQueiroz]

I need understand how to work the modbus.OnGetHreg(register)...

What I need. Each timer whats the master try read an expecific Holding Register, I need increment or Decrement the reading, but I put this loop and I get random values.... I think this is increment x every time what loop runs...
Any hint about how I can get my objective?

void loop() {
 if (mb.onGetHreg(101))
 {
  x++;
   mb.Hreg(101,x);

   if (digitalRead(pinToLED01))
   {
     digitalWrite(pinToLED01, LOW);
     digitalWrite(pinToLED02, HIGH);
   }
   else
   {
     digitalWrite(pinToLED01, HIGH);
     digitalWrite(pinToLED02, LOW);
   }
 }

  mb.task();
  yield();
}

[emelianov]

I'm afraid the goal is not clear for me.
Do you want to increase holding register value each time client reads the register ?

[WagnerDeQueiroz]

Hello @emelianov, I create a Holding register or Input Register,like 5 or 10 with a initial number, I like to check every time this register is read, it will be incremented or decremented with each reading.

Like

void setup() {
... 
mb.Hreg(101,x);
}
loop(){
 ...
  if mb.HregReaded(101)
{ x++;
  return x};
}

What the function modbus.OnGetHreg(register)...
does?

[fredlcore]

You have to do it like this:
Set up a callback function to be called every time a holding register is queried. In this function you change the register as you please:

uint16_t cb(TRegister* reg, uint16_t val) {
  x++;
  mb.Hreg(101, x);
  return val;
}

x must be a global variable, otherwise it will be out of scope.
In setup, you have to define the callback function (assuming that mb is your Modbus object):
mb.onGetHreg((101, cb);

[WagnerDeQueiroz]

This solution is AMAZING! I Will test soon! Thank you! Em sáb., 9 de dez. de 2023 às 06:31, fredlcore ***@***.***> escreveu:

…

You have to do it like this: Set up a callback function to be called every time a holding register is queried. In this function you change the register as you please: uint16_t cb(TRegister* reg, uint16_t val) { x++; mb.Hreg(101, x); return val; } x must be a global variable, otherwise it will be out of scope. In setup, you have to define the callback function (assuming that mb is your Modbus object): mb.onGetHreg((101, cb); — Reply to this email directly, view it on GitHub <#276 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AB4XIPOK5KE4R2XCXJQAREDYIQVXPAVCNFSM6AAAAAAWC6JGPCVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTQNBYGM2DKMBRG4> . You are receiving this because you authored the thread.Message ID: ***@***.***>

-- Wagner de Queiroz Be free with Linux

[fredlcore]

I just realized that it might have to be return x; if you also want to return the new value to the client that reads the value, because otherwise just the old value will be returned, but I'm not sure, I didn't test it out, so please report back here which solution works in the end so that others will know which one is correct.

[fredlcore]

Also, if you want to perform different actions based on the holding register address, you can do something like uint16_t addr = reg->address.address; and then perform actions based on the value of addr instead of just doing it with a fixed address of 101.