Programming the 18f452

[kennethkearney]

I’m trying to transfer a program from PIC 16F627 to PIC 18F452 and I’m having some trouble. All I want to do at the minute is set up a simple serial connection to the computer. I have it set up with a 20Mhz crystal and I’m using the same circuit board we set up for the 16f627. I think that should be ok, it’s a MAX232 to do the level shifting and we’re running the PIC at around 3.5 to 4 V

The program is :

#include <18f452.h>
#include <stdio.h>

#fuses nowdt,noprotect,hs
#FUSES NOBROWNOUT,NOLVP

#use delay (clock=20000000)

#define PC_RATE 19200
#define PC_TXD pin_b5 // RS232 Transmit
#define PC_RXD pin_b4 // RS232 Receive

#use rs232(baud = PC_RATE, xmit = PC_TXD, rcv = PC_RXD, bits = 8, ERRORS, stream = PC)

void put_PC(int8 c);

void put_PC (int8 c)
{
int high, low;

high = 0xf & (c >> 4);
low = 0xf & c;

if (high<=9)
{
fputc(48+high, PC);
}

else
{
fputc(55+high, PC);
}
delay_ms(1);

if (low<=9)
{
fputc(48+low, PC);
}

else
{
fputc(55+low, PC);
}

delay_ms(1);

fputc(0x20, PC); //puts a space between each of the hex numbers
delay_ms(1);
}

void main(void)
{
put_PC(0x20);

for (;;)
{
put_PC(0x20);
}
}



It should be really simple but it’s just not doing what it should. It works fine on the 16f627. Are there things to conisder when transferring designs from one device to another?

Can you help, I’m really stuck.

[PCM programmer]

I'm feeling feisty this morning, so I will do a "strict regime"
commentary on your post.

[kennethkearney]

Thanks PCM Programmer.

I'm not sure about the voltage (Vdd) thing, don't have the data sheet in front of me.

The max 232 is tried and tested, I didn't design the circuit but the output voltages are correct and it's the same circuit we used to power a PIC 16F627 we used to use so I presume it's ok (dangerous assukmption I know)

The put_PC() command is a function I made up myself. It doesn't output the ASCII(0x20) but the number 20. It takes each nibble and does a conversion according to the ASCII table and that's how it works.

As far as the program itself is concerned, today I found out that there's a bug in the CCS compiler in that it doesn't like PIC18 code too much. I'm using an older version and there's a bug in the assembler I think. I saw some threads on this site relating to it. When I leave out the 'for' loops, the program works fine but when we introduce any kind of loop, it crashes.

Don't know exactly why this is, will have to look into it further. Has anyone heard of this before and is there a fix? I bought the software in 2002 so my update period is long over, don't want to have to spend another $450 just to be able to use PIC18 devices!!

Any help would be great

[PCM programmer]

Do you have PCH or PCWH ? What version are you using ?

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buying a new compiler. Check the prices on this page:
http://www.ccsinfo.com/ccscorder.shtml