next topic »

[on:]

In summary, I can not get to work writing the slaves.

Reading, OK .. The Master, which received slaves shipped, (Function READ_HOLDING_REGISTERS) without problems... ; but in the other direction, no .. , Communication writing to slaves, always fails .. (function: 0x16 PRESET_MULTIPLE_REGISTERS)

IDE 1.0.2 y 1.0.3
Mega 2560
Modulo 485 de Sparfun
http://code.google.com/p/simple-modbus/
http://code.google.com/p/simple-modbus/downloads/list

MAESTRO

Code:

#include <SimpleModbusMaster1.h>

// led to indicate that a communication error is present
#define connection_error_led 13

//////////////////// Port information ///////////////////
#define baud 57600
#define timeout 1000
#define polling 200 // the scan rate


#define retry_count 3

// used to toggle the receive/transmit pin on the driver
#define TxEnablePin 23


enum
{
  PACKET1,
  PACKET2,
  // leave this last entry
  TOTAL_NO_OF_PACKETS
};

// Create an array of Packets for modbus_update()
Packet packets[TOTAL_NO_OF_PACKETS];

// The data from the PLC will be stored
// in the regs array
unsigned int regs[9];

void setup()
{
  Serial.begin (115200);
  
  // read 3 registers starting at address 0
  packets[PACKET1].id = 2;
  packets[PACKET1].function = READ_HOLDING_REGISTERS;
  packets[PACKET1].address = 0;
  packets[PACKET1].no_of_registers = 3;
  packets[PACKET1].register_array = regs;
  
  // write the 2 registers to the PLC starting at address 3
  packets[PACKET2].id = 2;
  packets[PACKET2].function = PRESET_MULTIPLE_REGISTERS;
  packets[PACKET2].address = 3;
  packets[PACKET2].no_of_registers = 6;
  packets[PACKET2].register_array = regs;
  
  // P.S. the register_array entries above can be different arrays
  
  // Initialize communication settings etc...
  modbus_configure(baud, timeout, polling, retry_count, TxEnablePin, packets, TOTAL_NO_OF_PACKETS);
  
  pinMode(connection_error_led, OUTPUT);
}

void loop()
{
  unsigned int connection_status = modbus_update(packets);
  
  if (connection_status != TOTAL_NO_OF_PACKETS)
  {
    digitalWrite(connection_error_led, HIGH);
    // You could re-enable the connection by:
    packets[connection_status].connection = true;
    delay (50);
    
  }
  else
    digitalWrite(connection_error_led, LOW);
  
  
  // LO QUE LLEGA
  Serial.print (regs[0]);  Serial.print (" ");
  Serial.print (regs[1]);  Serial.print (" ");
  Serial.print (regs[2]);
  
  Serial.print (" - ");
  
  Serial.print (packets[PACKET1].requests);  Serial.print (" ");
  Serial.print (packets[PACKET1].successful_requests);  Serial.print (" ");
  Serial.print (packets[PACKET1].incorrect_id_returned);  Serial.print (" ");
  Serial.print (packets[PACKET1].incorrect_function_returned);  Serial.print (" ");
  Serial.print (packets[PACKET1].incorrect_bytes_returned);  Serial.print (" ");
  Serial.print (packets[PACKET1].checksum_failed);  Serial.print (" ");
  Serial.print (packets[PACKET1].buffer_errors);  Serial.print (" ");
  Serial.print (packets[PACKET1].illegal_function);  Serial.print (" ");
  Serial.print (packets[PACKET1].illegal_data_address);  Serial.print (" ");
  Serial.print (packets[PACKET1].illegal_data_value);  Serial.print (" ");
  Serial.print (packets[PACKET1].misc_exceptions);  Serial.print (" ");
  Serial.print (packets[PACKET1].total_errors);
  
  Serial.print (" // ");

  // LO QUE ENVIO AL EXCLAVO
  
  regs[3] = 30;
  regs[4] = 40;
  regs[5] = 50;
  regs[6] = 60;  
  regs[7] = 70;
  regs[8] = 80;  
  
  Serial.print (regs[3]);  Serial.print (" ");
  Serial.print (regs[4]);  Serial.print (" ");
  Serial.print (regs[5]);  Serial.print (" ");
  Serial.print (regs[6]);  Serial.print (" ");
  Serial.print (regs[7]);  Serial.print (" ");
  Serial.print (regs[8]);
  
  Serial.print (" - ");

  Serial.print (packets[PACKET2].requests);  Serial.print (" ");
  Serial.print (packets[PACKET2].successful_requests);  Serial.print (" ");
  Serial.print (packets[PACKET2].incorrect_id_returned);  Serial.print (" ");
  Serial.print (packets[PACKET2].incorrect_function_returned);  Serial.print (" ");
  Serial.print (packets[PACKET2].incorrect_bytes_returned);  Serial.print (" ");
  Serial.print (packets[PACKET2].checksum_failed);  Serial.print (" ");
  Serial.print (packets[PACKET2].buffer_errors);  Serial.print (" ");
  Serial.print (packets[PACKET2].illegal_function);  Serial.print (" ");
  Serial.print (packets[PACKET2].illegal_data_address);  Serial.print (" ");
  Serial.print (packets[PACKET2].illegal_data_value);  Serial.print (" ");
  Serial.print (packets[PACKET2].misc_exceptions);  Serial.print (" ");
  Serial.print (packets[PACKET2].total_errors);  Serial.println (" ");

  delay (100);
  
}

ESCLAVO

Code:

#include <SimpleModbusSlave1.h>


//////////////// registers of your slave ///////////////////
enum
{    
  // just add or remove registers and your good to go...
  // The first register starts at address 0
  OUT1,    
  OUT2,        
  OUT3,
  

  REC1,
  REC2,
  REC3,
  REC4,
  REC5,
  REC6,
  
  TOTAL_ERRORS,
  // leave this one
  TOTAL_REGS_SIZE
  // total number of registers for function 3 and 16 share the same register array
};

unsigned int holdingRegs[TOTAL_REGS_SIZE]; // function 3 and 16 register array
////////////////////////////////////////////////////////////

void setup()
{
  Serial.begin (115200);
  
  
  /* parameters(long baudrate,
                unsigned char ID,
                unsigned char transmit enable pin,
                unsigned int holding registers size)
                
     The transmit enable pin is used in half duplex communication to activate a MAX485 or similar
     to deactivate this mode use any value < 2 because 0 & 1 is reserved for Rx & Tx
  */
  
  modbus_configure(57600, 2, 23, TOTAL_REGS_SIZE);

}

void loop()
{
  
  

  holdingRegs[TOTAL_ERRORS] = modbus_update(holdingRegs);
  for (byte i = 0; i < 3; i++)
  {
    holdingRegs[i] = analogRead(i+8);
    delayMicroseconds(500);    
  }


  // LO QUE ENVIA EL EXCLAVO
  Serial.print (holdingRegs[OUT1]);  Serial.print (" ");
  Serial.print (holdingRegs[OUT2]);  Serial.print (" ");
  Serial.print (holdingRegs[OUT3]);
  
  Serial.print ("  //  ");

  // RECIBE EL EXCLAVO
  
  Serial.print (holdingRegs[REC1]);  Serial.print (" ");
  Serial.print (holdingRegs[REC2]);  Serial.print (" ");
  Serial.print (holdingRegs[REC3]);  Serial.print (" ");
  Serial.print (holdingRegs[REC4]);  Serial.print (" ");
  Serial.print (holdingRegs[REC5]);  Serial.print (" ");
  Serial.print (holdingRegs[REC6]);
  
  Serial.print (" - ");

  Serial.println (holdingRegs[TOTAL_ERRORS]);
  
  delay (100);
}

The lib in the sketch, are edited to work with the serial 1

Any suggestions of what could be the mistake I'm making?

thank you very much
Greetings

[Reply #1 on:]

I answer myself ...

When the bus is free, at times it does not transmit anyone can produce erroneous readings due to noise in the pair
To avoid this, it puts a pull-up resistance in the A and a pull-down, in the B, thus, a potential is fixed to the case that all release the bus.

Interestingly, only affected the transmission, that appeared a "1" ghost, which falsified the total data received ..

http://en.wikipedia.org/wiki/File:Rs485-bias-termination.svg
http://en.wikipedia.org/wiki/RS-485
http://www.maximintegrated.com/app-notes/index.mvp/id/763

regards