PIC18F MODBUS COMMUNICATION

Hello everyone,
 
this is my first post so forgive/bear me if i am wrong, 
 
I wrote a code for MODBUS RTU SLAVE protocol for PIC18F46K22, which was working fine when i was in debug mode, data were travelling to and fro from PC SIDE MODPOLL software to PIC18F26K22 slave.
 
But when i programmed the device for standalone application, PC software gives me TIMEOUT ERROR. and if i again connect it in debug mode it again works fine.
 
any suggestion please where i am getting wrong.
 
Thanks
Regards

Which pins are you using for communication?
If they are analog capable, have you switched them to digital mode?
(The debugger switches some pins to digital mode for its own use. That won't happen in run mode.)
 
 
 

i am using tx1 and rx1 RC6 and RC7 which are analog pins as well but i had disable the analog function in my main code. also i am using RE2 pin for communication direction control of MAX-485. which is also i guess i had set as digital pin.
below is main code.
 
static bit disp_mode,prog_mode;
char read1,read2,read3,read4;

OSCCON = 0b01110011; //internal osc 16 Mhz HFINTOSC

ANSELA = 0x00; //DISABLE ANALOG CHANNELS
TRISA = 0b00000000; //LCD DATA PINS DIRECTION = OUTPUT

lcd = 0b00000000; //LCD DATA PINS DEFAULT VALUE

ANSELCbits.ANSC2 = 0; //digital pins and not analog
ANSELCbits.ANSC3 = 0; //digital pins and not analog
ANSELCbits.ANSC4 = 0; //digital pins and not analog
ANSELCbits.ANSC6 = 0; //digital pins and not analog TX1
ANSELCbits.ANSC7 = 0; //digital pins and not analog RX1


TRISCbits.TRISC4 = 1;
TRISCbits.TRISC3 = 1;

TRISCbits.TRISC2 = 1; // SET CAPTURE CCP1 AS INPUT PIN

ANSELE = 0x00; //DIGITAL PINS
ADCON0 = 0x00; //SHUT OFF ADC MODULE
TRISE = 0b00000000; //LCD CONTROL PINS and TX_RX CONTROL PINS DIRECTION = OUTPUT

ANSELB = 0x00;
TRISB = 0x3C; //PINS RB2 - RB5 SELECTED AS INPUTS.
PORTB = 0xFF; //DEFAULT VALUE OF INPUT PINS AS 1 (SINCE ACTIVE LOW INPUTS)
WPUB = 0x3C; // enable weak pull up of corresponding input pin
INTCON2bits.RBPU = 0; // enable weak pull up of port B;

init_lcd();
display_all("PCD-TFM-V2.0");
lcdcmd(0xC2);
display_all("PROCESS");
eunit.ui = read_eeprom(0x01);
tunit.ui = read_eeprom(0x02);
deci.ui = read_eeprom(0x03);

read1 = read_eeprom(0x04);
read2 = read_eeprom(0x05);
read3 = read_eeprom(0x06);
read4 = read_eeprom(0x07);
range_val.ui = (read1*1000)+(read2*100)+(read3*10)+read4;

__delay_ms(200);__delay_ms(200);__delay_ms(200);

lcdcmd(0xC2);
display_all("CONTROL");

k1 = read_eeprom(0x08);
k2 = read_eeprom(0x09);
k3 = read_eeprom(0x0A);
k4 = read_eeprom(0x0B);
k5 = read_eeprom(0x0C);
K_VALUE.f = ((k1+(k2*0.1)+(k3*0.01)+(k4*0.001)+(k5*0.0001)));

read1 = read_eeprom(0x16);
read2 = read_eeprom(0x17);
read3 = read_eeprom(0x18);
read4 = read_eeprom(0x19);
zero.ui = (read1*1000)+(read2*100)+(read3*10)+read4;

__delay_ms(200);__delay_ms(200);__delay_ms(200);

lcdcmd(0xC2);
display_all("DEVICES");
__delay_ms(200);__delay_ms(200);__delay_ms(200);

read1 = read_eeprom(0x1A);
read2 = read_eeprom(0x1B);
read3 = read_eeprom(0x1C);
read4 = read_eeprom(0x1D);
span.ui = (read1*1000)+(read2*100)+(read3*10)+read4;

read1 = read_eeprom(0x10);
read2 = read_eeprom(0x11);
read3 = read_eeprom(0x12);
read4 = read_eeprom(0x13);
ENTFREQ.f = (read1*1000)+(read2*100)+(read3*10)+read4;

read1 = read_eeprom(0x28);
read2 = read_eeprom(0x29);
read3 = read_eeprom(0x2A);
read4 = read_eeprom(0x2B);
ENTFR.f = (read1*1000)+(read2*100)+(read3*10)+read4;

sen_k.f=(ENTFR.f/ENTFREQ.f); //calculate the k-value
eeprom_read_object(0x20, &total.f, sizeof total.f);

lpm.f=((span.ui-zero.ui)/(float)range_val.ui);

I2CINIT();
init_timer0();
init_timer1();
init_ccp1();
init_esuart1();

lcdcmd(0x01);

i=0;
disp_mode=1;prog_mode=0;
state=1;dp=1;kmode=0;baud_sel=4;

database[20] = password.ub[1];database[21] = password.ub[0];
database[54] = xtal.ub[3];database[55] = xtal.ub[2];database[56] = xtal.ub[1];database[57] = xtal.ub[0];
database[62] = 0;database[63] = hw_version;
database[64] = 0;database[65] = sw_version;
rx_index=0;rx_done=0;tx_enable=0;
ovr_bit=0;fer_bit=0;tx_rx=0;
 
T0CONbits.TMR0ON = 1; // start timer0 for totalizer sampling
T1CONbits.TMR1ON = 1; // start timer1 for counting timeperiod
 

i have the raised the MCLR pin to VDD by using 10K resistor, power supply is also proper but i dnt knw about decoupling capacitor. i have used 0.1mfd capacitor on vdd and vss thats it.
 

But the issue is still there as, when i am first programming (not in debug mode)my device using pickit-3, the code works fine and so as modbus communication. but when switch off the power and switch it back on, except for modbus communicaton feature rest of the code works fine. on PC side modpoll software it gives me TIMEOUT error.
 
Please help me with this, i dnt knw whether something is wrong in my code or my programming methods are wrong.
 
i am using MPLAB X IDE V3.5 with xc8 compiler which is in free mode.
 

Maybe this thread might shed some light on the startup issues http://www.microchip.com/forums/FindPost/1015683

Hello Friends, Is there any code for PIC16F877a as a Modbus RTU Master to read holding register from slave.
 
Thanks
SILAMBU

well, here is a video where I explain how to apply  these piece of code
 
https://www.youtube.com/watch?v=ppxZgfDghPI
 
As I dont have access to upload any file, here is the fragments from them...
 
main.c

int main ( int argc, char** argv )
{
/* Set Up the uC. */
    setUp ( );
    
    setFrameMODBus ( slaveID, functionCode, startingAddressHi, startingAddressLo, 
                     numberOfRegistersHi, numberOfRegistersLo, PAYLOAD_MODBUS_TX ); 

    EnableInterrupt ( TMR0_INTERRUPT );
    EnableInterrupt ( GLOBAL_INTERRUPT );

/* Forever Loop */
    while ( TRUE )
    {
        if ( INT_1000ms )
        {
            writeModBusRegsiter ( PAYLOAD_MODBUS_TX );
            readModBusRegister ( PAYLOAD_MODBUS_RX );

            if ( modBusCRC ( PAYLOAD_MODBUS_RX, PAYLOAD_MODBUS_RX [ 3 ] + 3, READ_MODBUS_CRC ) )
                printfOutData ( );

            else
            {
                printf( "shit, CRC No valid \n");
                sprintf ( OLED_VAR, "CRC NOT OK!", CLEAR ); 
                OLEDText ( 5, 26, OLED_VAR, SIZE_TWO, OLED_WHITE );

                OLEDUpdateDisplay ( DDGRAM_CLEAR );
                }

            INT_3 = CLEAR;
            }

        } // forever loop.
    
    return ( EXIT_SUCCESS );
    } // main fuction.
[/code] 
 
 
MODBus.h

#define DE_RE_PIN               LATAbits . LATA0

//#define	DETECT_I2C_MODULE_PRESENT
#define I2C_BUS_1 
//#define MODBUS_UART1 
#define MODBUS_UART2 

#define	OLED_ADDRESS            0x78

unsigned char slaveID = 0x0A;
unsigned char functionCode = 0x03;
unsigned char startingAddressHi = 0x04;
unsigned char startingAddressLo = 0x00;
unsigned char numberOfRegistersHi = 0x00;
unsigned char numberOfRegistersLo = 0x07;
unsigned char CRCHi = 0x06;
unsigned char CRCLo = 0x07;


unsigned char OLED_Text_1 [ ] = "MODBus v1.0";
unsigned char OLED_Text_2 [ ] = "theRottingOne";

#define MAX_BUFFER_SIZE_TX             0x08        
#define MAX_BUFFER_SIZE_RX             0x40                     // 64 dec.
unsigned char PAYLOAD_MODBUS_TX [ MAX_BUFFER_SIZE_TX ];
unsigned char PAYLOAD_MODBUS_RX [ MAX_BUFFER_SIZE_RX ];

unsigned char OLED_VAR [ 6 ];     

#define WRITE_MODBUS            0X06
#define WRITE_MODBUS_CRC        0X00
#define READ_MODBUS_CRC         0X01


void setFrameMODBus ( unsigned char id, unsigned char functionCode,
                        unsigned char addHi, unsigned char addLo, 
                        unsigned char registerHi, unsigned char registerLo, 
                        unsigned char *ptrArrayTx );
void writeModBusRegsiter ( unsigned char *ptrArrayTx );
void readModBusRegister ( unsigned char *ptrArrayRx );
bit checkDataBuffer ( void );
bit modBusCRC ( unsigned char *ptrArray, unsigned char byteCount, unsigned char crcWR );
 [/code]
 
ModBus.c
 

void setFrameMODBus ( unsigned char id, unsigned char functionCode,
                        unsigned char addHi, unsigned char addLo, 
                        unsigned char registerHi, unsigned char registerLo, 
                        unsigned char *ptrArrayTx )
{
    ptrArrayTx [ 0 ] = id;
    ptrArrayTx [ 1 ] = functionCode;
    ptrArrayTx [ 2 ] = addHi;
    ptrArrayTx [ 3 ] = addLo;
    ptrArrayTx [ 4 ] = registerHi;
    ptrArrayTx [ 5 ] = registerLo;
    
    modBusCRC ( ptrArrayTx, WRITE_MODBUS, WRITE_MODBUS_CRC );
    
    } // setting frame values.


void writeModBusRegsiter ( unsigned char *ptrArrayTx )
{
    DE_RE_PIN = HIGH;                           // Activating trasnmition. 
    LED_0 = ON;

    for ( unsigned char i = 0; i < MAX_BUFFER_SIZE_TX; i++ )     // Transmitting 8bytes of info.
    {
#ifdef MODBUS_UART1    
        while( !TXSTA1bits . TRMT )             // While transmit shift register is full.
            ;
        TX1REG = *ptrArrayTx++;     			// Write the data byte to the USART.
#endif
#ifdef MODBUS_UART2    
        while( !TXSTA2bits . TRMT )             // While transmit shift register is full.
            ;
        TX2REG = *ptrArrayTx++;     			// Write the data byte to the USART.
#endif
        } 

    DE_RE_PIN = LOW;                            // Deactivationg transmition.
    LED_0 = OFF;
    
    } // write 8bytes of transmition.


void readModBusRegister ( unsigned char *ptrArrayRx )
{
  	unsigned char counter = CLEAR;
    signed char skipSearching = CLEAR;

    // The function will do the scan on the Rx pin until there is nothing in the bus.
    while ( !skipSearching ) 
        if ( !checkDataBuffer ( ) )
            skipSearching = SET;
        else
        {
            if ( counter < MAX_BUFFER_SIZE_RX )        
            {
#ifdef MODBUS_UART1    
                *ptrArrayRx = getChUSART1 ( );
#endif
#ifdef MODBUS_UART2    
                *ptrArrayRx = getChUSART2 ( );
#endif
                ptrArrayRx++;                           // Increment the string pointer
                counter++;
                }
            else
                printf ( " MAXIMUM BUFFER SIZE REACHED\n" );

            }
    
#ifdef DEBUG
//            printf ( "%d ", counter );
            printfBuffer ( PAYLOAD_MODBUS_RX );
#endif

    } // read n bytes from the buffer.


bit checkDataBuffer ( void )
{
    unsigned int j = CLEAR;

#ifdef MODBUS_UART1    
    while ( ( !dataRdyUSART1 ( ) ) && ( j < 30000 ) ) 
        j++;
        
    return RC1IF;
#endif    
    
#ifdef MODBUS_UART2    
    while ( ( !dataRdyUSART2 ( ) ) && ( j < 30000 ) ) 
        j++;
        
    return RC2IF;
#endif    
    
    }


bit modBusCRC ( unsigned char *ptrArray, unsigned char byteCount, unsigned char crcWR )
{
    unsigned int checkSum = 0xFFFF;
    
    if ( crcWR == READ_MODBUS_CRC )
    {
        for ( unsigned char i = 0x01; i <= byteCount; i++ )
        {
            checkSum = checkSum ^ ( unsigned int ) ptrArray [ i ];
            for ( unsigned char j = 8; j > 0; j-- )
                if ( checkSum & 0x0001 )
                    checkSum = ( checkSum >> 1 ) ^ 0xA001;
                else
                    checkSum >> = 0x01;
            }	

        unsigned char crcHi = checkSum;
        unsigned char crcLo = checkSum >> 0x08;
        
#ifdef DEBUG        
        printf( "[%d], [%d] \n", crcHi, crcLo );
#endif
        
        if ( ( ptrArray [ byteCount + 1 ] == crcHi ) && ( ptrArray [ byteCount + 2 ] == crcLo ) )
            return 0x01;
        } // if CRC functions comes froma a Read command.
        

    if ( crcWR == WRITE_MODBUS_CRC )
    {
        for ( unsigned char i = 0x00; i < WRITE_MODBUS; i++ )
        {
            checkSum = checkSum ^ ( unsigned int ) ptrArray [ i ];
            for ( unsigned char j = 8; j > 0; j-- )
                if ( checkSum & 0x0001 )
                    checkSum = ( checkSum >> 1 ) ^ 0xA001;
                else
                    checkSum >> = 0x01;
            }	

        ptrArray [ CRCHi ] = checkSum;
        ptrArray [ CRCLo ] = checkSum >> 0x08;
        
        return 0x00;
        } // if CRC functions comes froma a Write command.
    
    return 0;
    } // calculate and write CRC to the buffer.
  [/code]
 
 

                
                
            

rotting79
well, here is a video where I explain how to apply  these piece of code
 
https://www.youtube.com/watch?v=ppxZgfDghPI
 
As I dont have access to upload any file, here is the fragments from them...
 
main.c

int main ( int argc, char** argv )
{
/* Set Up the uC. */
 setUp ( );
 
 setFrameMODBus ( slaveID, functionCode, startingAddressHi, startingAddressLo, 
 numberOfRegistersHi, numberOfRegistersLo, PAYLOAD_MODBUS_TX ); 

 EnableInterrupt ( TMR0_INTERRUPT );
 EnableInterrupt ( GLOBAL_INTERRUPT );

/* Forever Loop */
 while ( TRUE )
 {
 if ( INT_1000ms )
 {
 writeModBusRegsiter ( PAYLOAD_MODBUS_TX );
 readModBusRegister ( PAYLOAD_MODBUS_RX );

 if ( modBusCRC ( PAYLOAD_MODBUS_RX, PAYLOAD_MODBUS_RX [ 3 ] + 3, READ_MODBUS_CRC ) )
 printfOutData ( );

 else
 {
 printf( "shit, CRC No valid \n");
 sprintf ( OLED_VAR, "CRC NOT OK!", CLEAR ); 
 OLEDText ( 5, 26, OLED_VAR, SIZE_TWO, OLED_WHITE );

 OLEDUpdateDisplay ( DDGRAM_CLEAR );
 }

 INT_3 = CLEAR;
 }

 } // forever loop.
 
 return ( EXIT_SUCCESS );
 } // main fuction.

 
MODBus.h

#define DE_RE_PIN LATAbits . LATA0

//#define DETECT_I2C_MODULE_PRESENT
#define I2C_BUS_1 
//#define MODBUS_UART1 
#define MODBUS_UART2 

#define OLED_ADDRESS 0x78

unsigned char slaveID = 0x0A;
unsigned char functionCode = 0x03;
unsigned char startingAddressHi = 0x04;
unsigned char startingAddressLo = 0x00;
unsigned char numberOfRegistersHi = 0x00;
unsigned char numberOfRegistersLo = 0x07;
unsigned char CRCHi = 0x06;
unsigned char CRCLo = 0x07;


unsigned char OLED_Text_1 [ ] = "MODBus v1.0";
unsigned char OLED_Text_2 [ ] = "theRottingOne";

#define MAX_BUFFER_SIZE_TX 0x08 
#define MAX_BUFFER_SIZE_RX 0x40 // 64 dec.
unsigned char PAYLOAD_MODBUS_TX [ MAX_BUFFER_SIZE_TX ];
unsigned char PAYLOAD_MODBUS_RX [ MAX_BUFFER_SIZE_RX ];

unsigned char OLED_VAR [ 6 ]; 

#define WRITE_MODBUS 0X06
#define WRITE_MODBUS_CRC 0X00
#define READ_MODBUS_CRC 0X01


void setFrameMODBus ( unsigned char id, unsigned char functionCode,
 unsigned char addHi, unsigned char addLo, 
 unsigned char registerHi, unsigned char registerLo, 
 unsigned char *ptrArrayTx );
void writeModBusRegsiter ( unsigned char *ptrArrayTx );
void readModBusRegister ( unsigned char *ptrArrayRx );
bit checkDataBuffer ( void );
bit modBusCRC ( unsigned char *ptrArray, unsigned char byteCount, unsigned char crcWR );

 
ModBus.c

void setFrameMODBus ( unsigned char id, unsigned char functionCode,
 unsigned char addHi, unsigned char addLo, 
 unsigned char registerHi, unsigned char registerLo, 
 unsigned char *ptrArrayTx )
{
 ptrArrayTx [ 0 ] = id;
 ptrArrayTx [ 1 ] = functionCode;
 ptrArrayTx [ 2 ] = addHi;
 ptrArrayTx [ 3 ] = addLo;
 ptrArrayTx [ 4 ] = registerHi;
 ptrArrayTx [ 5 ] = registerLo;
 
 modBusCRC ( ptrArrayTx, WRITE_MODBUS, WRITE_MODBUS_CRC );
 
 } // setting frame values.


void writeModBusRegsiter ( unsigned char *ptrArrayTx )
{
 DE_RE_PIN = HIGH; // Activating trasnmition. 
 LED_0 = ON;

 for ( unsigned char i = 0; i < MAX_BUFFER_SIZE_TX; i++ ) // Transmitting 8bytes of info.
 {
#ifdef MODBUS_UART1 
 while( !TXSTA1bits . TRMT ) // While transmit shift register is full.
 ;
 TX1REG = *ptrArrayTx++; // Write the data byte to the USART.
#endif
#ifdef MODBUS_UART2 
 while( !TXSTA2bits . TRMT ) // While transmit shift register is full.
 ;
 TX2REG = *ptrArrayTx++; // Write the data byte to the USART.
#endif
 } 

 DE_RE_PIN = LOW; // Deactivationg transmition.
 LED_0 = OFF;
 
 } // write 8bytes of transmition.


void readModBusRegister ( unsigned char *ptrArrayRx )
{
 unsigned char counter = CLEAR;
 signed char skipSearching = CLEAR;

 // The function will do the scan on the Rx pin until there is nothing in the bus.
 while ( !skipSearching ) 
 if ( !checkDataBuffer ( ) )
 skipSearching = SET;
 else
 {
 if ( counter < MAX_BUFFER_SIZE_RX ) 
 {
#ifdef MODBUS_UART1 
 *ptrArrayRx = getChUSART1 ( );
#endif
#ifdef MODBUS_UART2 
 *ptrArrayRx = getChUSART2 ( );
#endif
 ptrArrayRx++; // Increment the string pointer
 counter++;
 }
 else
 printf ( " MAXIMUM BUFFER SIZE REACHED\n" );

 }
 
#ifdef DEBUG
// printf ( "%d ", counter );
 printfBuffer ( PAYLOAD_MODBUS_RX );
#endif

 } // read n bytes from the buffer.


bit checkDataBuffer ( void )
{
 unsigned int j = CLEAR;

#ifdef MODBUS_UART1 
 while ( ( !dataRdyUSART1 ( ) ) && ( j < 30000 ) ) 
 j++;
 
 return RC1IF;
#endif 
 
#ifdef MODBUS_UART2 
 while ( ( !dataRdyUSART2 ( ) ) && ( j < 30000 ) ) 
 j++;
 
 return RC2IF;
#endif 
 
 }


bit modBusCRC ( unsigned char *ptrArray, unsigned char byteCount, unsigned char crcWR )
{
 unsigned int checkSum = 0xFFFF;
 
 if ( crcWR == READ_MODBUS_CRC )
 {
 for ( unsigned char i = 0x01; i <= byteCount; i++ )
 {
 checkSum = checkSum ^ ( unsigned int ) ptrArray [ i ];
 for ( unsigned char j = 8; j > 0; j-- )
 if ( checkSum & 0x0001 )
 checkSum = ( checkSum >> 1 ) ^ 0xA001;
 else
 checkSum >> = 0x01;
 } 

 unsigned char crcHi = checkSum;
 unsigned char crcLo = checkSum >> 0x08;
 
#ifdef DEBUG 
 printf( "[%d], [%d] \n", crcHi, crcLo );
#endif
 
 if ( ( ptrArray [ byteCount + 1 ] == crcHi ) && ( ptrArray [ byteCount + 2 ] == crcLo ) )
 return 0x01;
 } // if CRC functions comes froma a Read command.
 

 if ( crcWR == WRITE_MODBUS_CRC )
 {
 for ( unsigned char i = 0x00; i < WRITE_MODBUS; i++ )
 {
 checkSum = checkSum ^ ( unsigned int ) ptrArray [ i ];
 for ( unsigned char j = 8; j > 0; j-- )
 if ( checkSum & 0x0001 )
 checkSum = ( checkSum >> 1 ) ^ 0xA001;
 else
 checkSum >> = 0x01;
 } 

 ptrArray [ CRCHi ] = checkSum;
 ptrArray [ CRCLo ] = checkSum >> 0x08;
 
 return 0x00;
 } // if CRC functions comes froma a Write command.
 
 return 0;
 } // calculate and write CRC to the buffer.

@ qhb
 
thanks for your help