can't transfer bytes array from pic18f4550 to another one using usart

[max_evil]

im trying to transfer bytes array from pic18f4550 to another one using usart and debug it using USB on one of them, the problem is that the reciver pic receives 2 bytes! on the first tx and then does not receive anything. im using the following code

 OpenUSART (USART_TX_INT_OFF &
             USART_RX_INT_OFF &
             USART_ASYNCH_MODE &
             USART_EIGHT_BIT &
             USART_CONT_RX &
             USART_BRGH_HIGH, 131);

static unsigned char send_dummy[4];
static unsigned char recv_dummy[4];

int n_recv = 0;
int n_send = 0;
int send_bytes( unsigned char* bytes, int len)
{
    int i = 0;
    int n = 0;
    for ( i = 0; i < len; i++)
    {
        while(BusyUSART());
        WriteUSART( bytes[i] ); // send byte
        DELAY_US_130
        n++;
    }

    return n;
}


int recv_bytes( unsigned char *bytes, int len)
{
    int i = 0;
    int n = 0;
    for ( i = 0; i < len; i++)
    {
      if ( DataRdyUSART() ) // is data aviliable in buffer?
        {
            bytes[i] = ReadUSART();
            n++;
        }else
        {
            // no data left return
            return n;
        }
     }

    return n;
}

// send load table
void send_lt(void)
{
    /* test values */
    send_dummy[0] = 0xD1;
    send_dummy[1] = 0xD2;
    send_dummy[2] = 0xD3;
    send_dummy[3] = 0xD4;
    n_send = send_bytes( send_dummy, sizeof(send_dummy));
}


void recv_lt(void)
{
    memset( recv_dummy, 0, sizeof( recv_dummy));
    n_recv = recv_bytes( recv_dummy, sizeof( recv_dummy));
       
   ....
}

--------

the first main code
void main ()
{
   
    while(1)
    {
        // check if we have something to read
        if( DataRdyUSART() )

            recv_lt();
            send_lt();

        }
}

the second main

void main()
{
         send_lt();
         recv_lt();

         LED = ~(LED);
         DELAY_MS_500
}

the compiler is C18 and 20Mhz clock with PLL. please advice !

 

[tgootee]

Wouldn't you want to write to it when it's NOT busy?

 

[AveztruZ]

I don't know how this library is working because I'm usually setting registers instead.... But I've got some issues like this last week and I was not checking FERR and OERR registers (receiving errors)... you need to add in your code something like:

If (FERR||OERR){
CREN = 0;
delay_us(5);
CREN = 1;
RCIE = 1;// in case of using interrupt
}

Read about this registers on datasheet and check if they are treated by this library....

I also suggest you to use interrupt for receiver... And you will not spend time in your main code checking if there is data on receiver buffer or not. :grin:

- - - Updated - - -

I don't know how this library is working because I'm usually setting registers instead.... But I've got some issues like this last week and I was not checking FERR and OERR registers (receiving errors)... you need to add in your code something like:

If (FERR||OERR){
CREN = 0;
delay_us(5);
CREN = 1;
RCIE = 1;// in case of using interrupt
}

Read about this registers on datasheet and check if they are treated by this library....

I also suggest you to use interrupt for receiver... And you will not spend time in your main code checking if there is data on receiver buffer or not. :grin:

 

[paulfjujo]

hello,

you have to use intterrupt mode for receiving data.
and use a software protocole like XON,XOFF,
or ACk ENQ,
or by adding extra I/O hardware for DTR,CTS
management.
so exchange of data will allways be synchronized and reliable.