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paclark
Joined: 02 Mar 2004
Posts: 4
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| PIC18 Bootloader -- RS232 Problems |
 Posted: Wed Mar 03, 2004 4:45 pm |
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Hello,
I am using the Tiny PIC bootloader from (http://www.ac.ugal.ro/staff/ckiku/software/picbootloader.htm) on a PIC18F458 @40MHz and it works beautifully. However, if the C code that is bootloaded to the PIC tries to use the RS232 port, the output is not displayed in a terminal program. I've tried numerous baud rates and have had no success. If I load the C code directly to the PIC without the bootloader (PicStart) the output is displayed to the terminal program.
| Code: | #include <18F458.h>
#fuses HS,NOWDT,NOPROTECT,PUT, NOLVP
#use delay(clock=40000000)
#use rs232(baud=19200,parity=N,bits=8,xmit=PIN_D6,rcv=PIN_D7,stream=PC)
#int_global
void dummy() {}
void main() {
fprintf (PC,"Bootloader OK");
while (1){ \\Blink LED on D0
output_high(PIN_D0);
delay_us(35000);
output_low(PIN_D0);
delay_us(35000);
}
} |
Any suggestions on why the bootloader is disrupting the communication? I have tried changing the #USE RS232 to pins D7 and D6 and that works fine even with the bootloader but that requries a hardware change between bootload and code launch for terminal output.
Regards,
Patrick |
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Guest
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| Posted: Wed Mar 03, 2004 10:21 pm |
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Try putting the "errors" switch in your #use rs232 statement.
Hope that helps. |
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Guest
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| Re: PIC18 Bootloader -- RS232 Problems |
| Posted: Thu Mar 04, 2004 2:59 am |
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| paclark wrote: | However, if the C code that is bootloaded to the PIC tries to use the RS232 port, the output is not displayed in a terminal program.
Any suggestions on why the bootloader is disrupting the communication?
Patrick |
patrick,
this is a common problem when using bootloaders. it is a result of the bootloader code configuring various serial port registers prior to your program running AND/OR an error condition already present when your program goes to configure the serial port. the second condition can *sometimes* be resolved as noted above. but that is the trivial case...
this problem took a lot of time for me to figure out when it first happened to me.
ok, how to solve? one way, and i believe the best way, is to get out the datasheet and look up all of the serial port related registers. then, at the beginning of your program, reset these registers to their power-up values prior to doing anything else. yes, i know this is a pain the butt. but the bootloader is leaving the PIC (specifically the USART) in a mode which isn't getting configured properly by the CCS initialization. so you need to help it along by reinitializing those registers.
recently i actually had this problem in reverse -- i wanted to jump back into the bootloader code from my program, thus forcing a code update on the device. i had a lot of fun with that, let me tell you. ultimately it was the same problem as above -- the bootloader wants the hardware in a known state (as close to power up as possible), and my program code had to make provisions to put it back in that state. in any case, you should be able to quickly adopt the code below to fix your situation. not all of the registers i show need to be reset for your situation, so you could experiment and cull some out. for example, to re-enter my bootloader, i had to reinitialize all of the interrupt and timing registers. in your case you probably don't need to touch these, but the baud rate generator etc registers you will have to fix up.
jds
| Code: |
// used to reset to power-up defaults for bootloader reentry.
// 18Fxxx special purpose register power up values:
// location // power-up value
#byte PCL = 0xFF9
#byte FSR0H = 0xFEA // 0x00
#byte FSR0L = 0xFE9 // 0x00
#byte INTCON = 0xFF2 // 0x00
#byte INTCON2= 0xFF1 // 0xF5
#byte INTCON3= 0xFF0 // 0xC0
#byte FSR0H = 0xFEA // 0x00
#byte STATUS = 0xFD8 // 0x00
#byte TMR0H = 0xFD7 // 0x00
#byte TMR0L = 0xFD6 // 0x00
#byte T0CON = 0xFD5 // 0xFF
#byte TMR1H = 0xFCF // 0x00
#byte TMR1L = 0xFCE // 0x00
#byte T1CON = 0xFCD // 0x00
#byte TMR2 = 0xFCC // 0x00
#byte PR2 = 0xFCB // 0xff
#byte T2CON = 0xFCA // 0x00
#byte SSPADD = 0xFC8 // 0x00
#byte SSPSTAT= 0xFC7 // 0x00
#byte SSPCON1= 0xFC6 // 0x00
#byte SSPCON2= 0xFC5 // 0x00
#byte TMR3H = 0xFB3 // 0x00
#byte TMR3L = 0xFB2 // 0x00
#byte T3CON = 0xFB1 // 0x00
#byte SPBRG = 0xFAF // 0x00
#byte RCREG = 0xFAE // 0x00
#byte TXREG = 0xFAD // 0x00
#byte TXSTA = 0xFAC // 0x02
#byte RCSTA = 0xFAB // 0x00
#byte PIR2 = 0xFA1 // 0x00
#byte PIR1 = 0xF9E // 0x00
#byte PIE1 = 0xF9D // 0x00
#byte TRISC = 0xF94 // 0xff
#byte TRISB = 0xF93 // 0xff
#byte TRISA = 0xF92 // 0x3f
#byte PORTC = 0xF82 // 0x00
#byte PORTB = 0xF81 // 0x00
#byte PORTA = 0xF80 // 0x00
void jump_to_bootloader() {
disable_interrupts(GLOBAL);
internal_eeprom(INCREMENT16, EEPROM_FLASH_ATT, DONT_CARE);
display_message(MSG_FWUPDATE,MOD_NONE,TIMEOUT_NONE);
delay_ms(250); // >200ms for downloader sync
FSR0H = 0x00; // clean up special purpose registers
PIR1 = 0x00;
PIR2 = 0x00;
TMR2 = 0x00;
T2CON = 0x00;
PIE1 = 0x00;
PR2 = 0xff;
STATUS = 0x00;
TMR0H = 0x00;
TMR0L = 0x00;
T0CON = 0xFF;
INTCON = 0x00;
INTCON2= 0xff;
INTCON3= 0xc0;
T1CON = 0x00;
TMR1L = 0x00;
TMR1H = 0x00;
SPBRG = 0x00;
TXSTA = 0x02;
RCSTA = 0x00;
TXREG = 0x00;
RCREG = 0x00;
reset_cpu(); // then jump to reset vector
}
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paclark
Joined: 02 Mar 2004
Posts: 4
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| Posted: Thu Mar 04, 2004 12:53 pm |
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Beautiful. Thank you jds for your help. Might I ask which bootloader you use?
Patrick |
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jds-pic2
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