Hello everyone faced such a problem, there are two arduino, configure the modbus protocol, I encountered that the master sends requests to the slave, but slave does not receive them.
Connected via rs485, RE DE pins are connected via 8 pin.
With EASYtransfer library everything works, but modbus is needed
Master
/**
* Modbus master example 1:
* The purpose of this example is to query an array of data
* from an external Modbus slave device.
* The link media can be USB or RS232.
*
* Recommended Modbus slave:
* diagslave http://www.modbusdriver.com/diagslave.html
*
* In a Linux box, run
* "./diagslave /dev/ttyUSB0 -b 19200 -d 8 -s 1 -p none -m rtu -a 1"
* This is:
* serial port /dev/ttyUSB0 at 19200 baud 8N1
* RTU mode and address @1
*/
#include <ModbusRtu.h>
// data array for modbus network sharing
uint16_t au16data[16];
uint8_t u8state;
/**
* Modbus object declaration
* u8id : node id = 0 for master, = 1..247 for slave
* u8serno : serial port (use 0 for Serial)
* u8txenpin : 0 for RS-232 and USB-FTDI
* or any pin number > 1 for RS-485
*/
Modbus master(0,0,8); // this is master and RS-232 or USB-FTDI
/**
* This is an structe which contains a query to an slave device
*/
modbus_t telegram;
unsigned long u32wait;
void setup() {
master.begin( 19200 ); // baud-rate at 19200
master.setTimeOut( 2000 ); // if there is no answer in 2000 ms, roll over
u32wait = millis() + 1000;
u8state = 0;
}
void loop() {
switch( u8state ) {
case 0:
if (millis() > u32wait) u8state++; // wait state
break;
case 1:
telegram.u8id = 5; // slave address
telegram.u8fct = 3; // function code (this one is registers read)
telegram.u16RegAdd = 1; // start address in slave
telegram.u16CoilsNo = 4; // number of elements (coils or registers) to read
telegram.au16reg = au16data; // pointer to a memory array in the Arduino
master.query( telegram ); // send query (only once)
u8state++;
break;
case 2:
master.poll(); // check incoming messages
if (master.getState() == COM_IDLE) {
u8state = 0;
Serial.println(au16data[0]);
u32wait = millis() + 100;
}
break;
}
}
Slave
/**
* Modbus slave example 2:
* The purpose of this example is to link a data array
* from the Arduino to an external device.
*
* Recommended Modbus Master: modpoll
* http://www.modbusdriver.com/modpoll.html
*/
#include <ModbusRtu.h>
// data array for modbus network sharing
uint16_t au16data[16] = {
3, 1415, 9265, 4, 2, 7182, 28182, 8, 0, 0, 0, 0, 0, 0, 1, -1 };
/**
* Modbus object declaration
* u8id : node id = 0 for master, = 1..247 for slave
* u8serno : serial port (use 0 for Serial)
* u8txenpin : 0 for RS-232 and USB-FTDI
* or any pin number > 1 for RS-485
*/
Modbus slave(5,0,8); // this is slave @1 and RS-232 or USB-FTDI
void setup() {
slave.begin( 19200); // 19200 baud, 8-bits, even, 1-bit stop
}
void loop() {
slave.poll( au16data, 16 );
}