Usart problem with 18F4550

**maus** · - 5th March 2006, 21:42

thanks steve for helping me on the way again.
i figured it out with your sample code and i'm back on track.

thx again

**f_lez** · - 2nd November 2009, 01:21

Oh I clapped my hands when I found this, thought i had got a working example of hserout...

didnt work for me.........

I changed it a little as I like to run at OSC 48 etc, and dont use a boot loader, and didnt need hserin, so just did a hserout and a 1 second pause to see if i could receive at the PC end, but I get the wrong chars, usually =_Y=_Y etc repeated

Code:

    '   Baudrate : 9600 Bauds
    '   Method :   Polling USART interrupts flags

    '   Pic Definition
    '   ==============
        ' Using PIC 18F2550 @  48 MHZ        '
        
        DEFINE OSC 48
        clear          
        ADCON1 = %00001111
        
    '   Hardware configuration
    '   ======================
        TRISC  = %10000000    ' PORTC.7 is the RX input
                              ' PORTC.6 is the TX output
    
    '   Serial communication definition
    '   ===============================
    '   Using internal USART and MAX232 to interface to PC
    '
        DEFINE HSER_RCSTA 90h ' enable serial port, 
                              ' enable continuous receive
                              '
        DEFINE HSER_TXSTA 20h ' enable transmit, 
                              ' BRGH=1
                              '
        
        
        DEFINE HSER_BAUD 9600                   
        
        DEFINE HSER_CLROERR  1 ' automatic clear overrun error  
        
    '   Alias definition
    '   ================
        RCIF VAR PIR1.5     ' Receive  interrupt flag (1=full , 0=empty)
        TXIF VAR PIR1.4     ' Transmit interrupt flag (1=empty, 0=full)
        
    '   Variable definition
    '   ===================
        SerialData var byte
        
    '   Hardware initialisation
    '   =======================
        pause 10 ' safe start-up delay
    
Main:
pause 1000
toggle portb.0

       hserout [65,10,13] ' send it

    goto main

Also portC.1 goes high ?

led flashes 1 second on and 1 second off so i'd say cpudiv etc is right.

Have i done anything obviously wrong?

**f_lez** · - 2nd November 2009, 14:16

ok double checked the hardware on the pc side, its a pl2303/usb cable, as my laptop nhas no com: ports.

if i short pins 2/3 then i see what i type, so the hardware to that point is working.

i then plug this into my dev board, which has a max232 on it, this is connected to the PIC via a dip switch on rc6/rc7. if i disconnect it from the pic with the switches and then short these, i see what i type again, so the max 232 is working both ways...

I flip the switches and reconnect to the pic, and i get garbage on screen, about once a second, and the chr counter advances by 3, so its almost right, but not quite........

**aratti** · - 2nd November 2009, 15:08

Below the EUSART setting for 48 Mhz as per Mr E pic calculator.

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_CLROERR 1 ' Clear overflow automatically
DEFINE HSER_SPBRG 225 ' 9600 Baud @ 48MHz, 0,0%
SPBRGH = 4
BAUDCON.3 = 1 ' Enable 16 bit baudrate generator

Al.

**f_lez** · - 2nd November 2009, 18:06

I did have a look at the Mister_e tool, but it said it needed a dll i didnt have.

Also still same, but then i found baudcon.4=1.......bingo! (Ok a friend pointed to it!)

Seems i needed my bits the other way up...

Other issue still remains, portc.1=high, but i see nothing in the above to cause it?

No doubt its a quirk of using the Hw instead of the software routine.

I could always consider it a power light....