18F4550 Not Recognised

[Funky Gibbon]

Hi Steve,

I've been using 18F452's so this 18F4550 is all new to me, you think 20mhz is too slow? you could be right, should i dump the crystal and use the internal osc, i think i saw in the settings that it had an internal osc, i've built a new dev board just for this controller as the pinout is slightly different to the F452, i've still kept a max232 on the board for serial comms.
I've been looking at the Bootloader for the F452, do you think it would be possible to make it function on the FR4550 with some adjustment, like i said the F4550 is new to me so forgive me if im talking cr*p

Shaun

[Bruce]

A 20MHz crystal is fine as long as you set the proper config word options.

Below are my config settings for the 18F4550 from my 18F4550.INC file in my
PBP directory. I have edited the default settings in this PBP header file for
the 18F4550 to be compatible with the Microchip USB boot-loader.

        NOLIST
    ifdef PM_USED
        LIST
        "Error: PM does not support this device.  Use MPASM."
        NOLIST
    else
        LIST
        LIST p = 18F4550, r = dec, w = -311, f = inhx32
        INCLUDE "P18F4550.INC"	; MPASM  Header
        CONFIG PLLDIV=5,CPUDIV=OSC1_PLL2,USBDIV=2,FOSC=HSPLL_HS,FCMEM=OFF,IESO=OFF
	CONFIG VREGEN=ON,CCP2MX=ON,WDT=OFF,WDTPS=32768,PBADEN=OFF,PWRT=OFF,MCLRE=ON
	CONFIG LPT1OSC=OFF,BOR=ON,BORV=2,STVREN=ON,LVP=OFF,ICPRT=OFF,XINST=OFF,DEBUG=OFF
	CONFIG WRTB=ON
        NOLIST
    endif
        LIST
EEPROM_START	EQU	0F00000h
BLOCK_SIZE	EQU	32

PLLDIV=5 ' This sets the PLL Postscaler to divide the primary osc input by 5
providing 4MHz to the 96MHz PLL. The 96MHz PLL input must always be 4MHz
as shown in the data sheet.

CPUDIV=OSC1_PLL2 ' This sets the PLL Postscaler to divide the 96MHz PLL
output by 2 providing a 48MHz clock to the CPU.

USBDIV=2 ' This divides the 96MHz PLL output by 2 providing 48MHz to the
USB core.

FOSC=HSPLL_HS ' This enables HSPLL for high-speed crystal/resonator.

If you plan to use the Microchip USB boot-loader with PBP, then insert this in
the top section of your code;

DEFINE OSC 48 ' 20MHz crystal with HSPLL enabled = 48MHz
DEFINE RESET_ORG 800h ' Reset Vector = 800h When Using Microchip USB Boot-Loader

[Funky Gibbon]

Thanks Bruce, i shall give it a try and let you know what happens

Shaun