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Serial Communication with dsPIC30F4011

Discussion in 'Microcontrollers, Programming and IoT' started by DJPat, Nov 4, 2016.

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  1. DJPat


    Nov 4, 2016
    Hi..I've been trying to get my serial communication on the dsPIC to work. I need to be able to transmit and receive at least one character but all I seem to get is an junk transmission. I'm not sure if my code is right. I've tried a max232 circuit and an off the shelf usb-to-serial bridge. Both give the same output. I've also made sure the baud rates are correct. Please help.

    Here's my code:
    //------------------------------------------- Defines
    #include <p30f4011.h>
    #include <xc.h>
    #include <libpic30.h>
    #include <ports.h>
    #include <dsp.h>
    #include <math.h>

    #define FCY (unsigned long) 30000000 //add your operating frequency
    #define UART1_BAUD 9600
    #define UART2_BAUD 9600
    #define UBRG1_VALUE (FCY/UART1_BAUD)/16 - 1
    #define UBRG2_VALUE (FCY/UART2_BAUD)/16 - 1
    //------------------------------------------ Config bits
    // Configuration settings
    _FOSC(CSW_FSCM_OFF && FRC_PLL16); // Fosc=16x7.5MHz, i.e. 30 MIPS
    // 16 x 7.5=120 MHz
    _FWDT(WDT_OFF); // Watchdog timer off
    _FBORPOR(MCLR_EN); // Disable reset pin
    int main(void)
    unsigned char MSG[]= "o";

    while (1)
    // WriteCharToUART1(13);
    return 0;

    void OpenUART1(void)
    TRISFbits.TRISF2 = 1;
    TRISFbits.TRISF3 = 0;

    U1MODEbits.ALTIO = 0;
    U1MODEbits.PDSEL = 0; // 8 bits no parity
    U1MODEbits.STSEL = 0; //1 stop bit
    U1BRG = 194; //calculated according to baud rate 9600

    U1MODEbits.UARTEN = 1; //enable tx rx pins
    U1STAbits.UTXEN = 1; // enable transmit

    char BusyUART1 (void)
    return 1;
    IFS0bits.U1TXIF =0;
    return 0;

    void PrintStringUART1 (unsigned char *String)
    while (*String)
    WriteCharToUART1 (*String++);
    void WriteCharToUART1 (unsigned char Data)
    U1TXREG = Data;
    while (BusyUART1()); __delay32(15000000);
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Hi Pat, welcome to EP.

    Please use the 'Insert... Code' button next time to make your post better readable.

  3. DJPat


    Nov 4, 2016
    Alright, thank you. I didn't know there was an option for that.. I see it now:)
  4. NorthGuy


    Mar 24, 2016
    The oscillator is 7.37, not 7.5 MHz. So the baud should be 191 instead of 194. Not a big difference, but who knows, combined with the oscillator error of 2%, might be enough to screw up.
  5. Amar Dhore

    Amar Dhore

    Dec 2, 2015
    In a while loop
    while (1)
    PrintStringUART1(MSG); //you are increasing index in a while loop. This function is a bit fishy
    and your array unsigned char MSG[]= "o"; is of a size 1 and

    in the function PrintStringUART1() you are increasing you array index which I think spitting out the garbage because its not initialize.

    try this:
    char MSG[]= "Hello World";

    when you send a message, count the byte
    while(length of a string)
    U1TXREG = MSG[i++];
    wait for PIC to send a char
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