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pasini
Joined: 12 Dec 2005
Posts: 50
Location: Curitiba - Brazil
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| USB CDC / PIC18LF2550 |
 Posted: Thu Nov 27, 2008 8:19 am |
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PIC18LF2550 - MPLAB 8.10 CCS4.082
Hi, I can exchange data with the computer (hyperterminal) as CDC device but suddenly PIC stops working. It is powered but it seams to crash. I think the connection with computer is lost. The crystal I am using is 20MHz, 3.3V (power from USB + 3.3V regulator) and serial UART at 4800bps.
Also, when I type something ('1','2','3' or '4') the usb crashes.
It is as simple as an USB<-->UART @ 4800bps. What I am doing wrong ?
Thanks in advance, Luiz
My code is:
| Code: | #define __USB_PIC_PERIF__ 1
#include <18F2550.h>
#device *=16
#device ADC=10
#fuses HSPLL,NOWDT,NOPROTECT,NOLVP,NODEBUG,USBDIV,CPUDIV1,VREGEN,PLL5
#use delay(clock=48000000)
#use rs232(baud=4800,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,stream=GPS)
#case
#include <usb_cdc.h>
#include <STDLIB.H>
#define PIN_LED PIN_A0
#define LED_ON() output_low(PIN_LED)
#define LED_OFF() output_high(PIN_LED)
#define EN_GPS() output_high(PIN_A1)
#define DIS_GPS() output_low(PIN_A1)
#define OK 1
#define NOK 0
char carac_rs232=0;
char carac_usb;
void main(void)
{
usb_init();
while(!usb_cdc_connected());
EN_GPS();
printf(usb_cdc_putc,"Usb READY\n\r");
while(1)
{
if(usb_cdc_kbhit())
{
carac_usb = usb_cdc_getc();
//usb_cdc_putc(carac_usb);
switch(carac_usb)
{ case '1':
fputs("$PTYCRMC,1\015\012",GPS);
break;
case '2':
fputs("$PTYCRMC,0\015\012",GPS);
break;
case '3':
fputs("$PTYCGGA,1\015\012",GPS);
break;
case '4':
fputs("$PTYCGGA,0\015\012",GPS);
break;
}
}
if(kbhit(GPS))
{ LED_ON();
carac_rs232 = getc(GPS);
usb_cdc_putc(carac_rs232);
LED_OFF();
}
}// End While
}// End Main
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Ttelmah
Guest
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| Posted: Thu Nov 27, 2008 10:02 am |
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What capacitors have you go on the USB regulator pin?. What capacitors on the PIC supply itself?. How are you powering the RS232 transceiver?.
Best Wishes |
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Ttelmah
Guest
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| Posted: Thu Nov 27, 2008 10:41 am |
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Whoa.
Re-reading your post, you are running the PIC off 3.3v, with an external 3.3v regulator?. First, you are running too fast for this. The maximum spcified frequency for 3.3v operation, is just 18.6MHz. You need 4.2v, for 48MHz operation. I'd suggest you connect the PIC directly to the USB supply. The PIC also requires that it's supply is always _greater_ than the Vusb supply (even when using an external regulator). You also have Vregen set, which enables the internal 3.3v regulator. To run with an external regulator, requires 'NOVREGEN' The internal regulator (obviously), cannot deliver 3.3v, when driven from 3.3v.
Best Wishes |
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