I mean that the serial port number from 0 to 3 could be declared at the object, but this should be allowed only depeding on the Microcontroller. Then
Any Arduino ONE or Duemilia would be allowed to use only port 0;
An Arduino Mega could use any port from 0 to 3 or even include several Modbus objects associated to different ports.
Indeed I'm planning to extend this feature to a custom PCB based on an ATMEGA1284P.
The code should start with something like this:
HardwareSerial port = Serial;
class ModbusSlave {
public:
ModbusSlave();
ModbusSlave(unsigned char serno);
void configure(unsigned char slave, long baud, char parity);
};
// empty constructor
ModbusSlave::ModbusSlave() {
this->serno = 0;
this->txenpin = 0;
}
ModbusSlave::ModbusSlave(unsigned char serno) {
this->serno = (serno > 3) ? 0 : serno;
this->txenpin = 0;
}
/*
* configure(slave, baud, parity, txenpin)
*
* sets the communication parameters for of the serial line.
*
* slave: identification number of the slave in the Modbus network (1 to 127)
* baud: baudrate in bps (typical values 9600, 19200... 115200)
* parity: a single character sets the parity mode (character frame format):
* 'n' no parity (8N1); 'e' even parity (8E1), 'o' for odd parity (8O1).
* txenpin: arduino pin number that controls transmision/reception
* of an external half-duplex device (e.g. a RS485 interface chip).
* 0 or 1 disables this function (for a two-device network)
* >2 for point-to-multipoint topology (e.g. several arduinos)
*/
void ModbusSlave::configure(unsigned char slave, long baud, char parity)
{
this->slave = slave;
switch( serno ) {
case 1:
port = Serial1;
break;
case 2:
port = Serial2;
break;
case 3:
port = Serial3;
break;
default:
port = Serial;
break;
}
port.begin(baud);
if (txenpin > 1) { // pin 0 & pin 1 are reserved for RX/TX
pinMode(txenpin, OUTPUT);
digitalWrite(txenpin, LOW);
}
return;
}
How can I implement this depending on the microcontroller?
It's useless but I like it. There's no extra code for this, isn't it?
There are #defined variable that define which board is selected when compiling. Why can't you use them?
I'd like to use this but I didn't know how. I was unsuccessfully trying to look for any example. The solution provided by pYro_65 is good for Arduino based CPUs, but I would like to use it on an ATMEGA1284P or other controllers. How can I do it?
Thanks for your help! I'll try it as soon as possible.
You can use the same method to select a USART rather than an arduino HardwareSerial object, or add a 1284 to arduino ( which people have already done ).
The 'this->' is not useless in this situation, class declarations can be big, the 'this->' makes it obvious that the variable belongs to the class. People using the class for the first time will have an easier job modifying/understanding the class.
Anything that can remove a person from assuming something is beneficial.
I've been trying to implement this "template" instances, but it's the first time I find them. Could you show me how to do it? Just a link to anywhere or a short example would be fine for me.
As you want to use it on a non-standard Arduino, you will either have to modify an Arduino core for that processor ( many people have posted mods for many chips ), or use the AVR functionality directly, skipping the Arduino libraries. If you use an arduino core, this should work with any avr that supports up to 4 serial ports.
