[alllanb]

Is it possible to use a Pic 16F887 in place of a 16f877A in the old core as I have two at present and would like to try building a core module.
I am in Cape Town South Africa and parts are not so easy and cheap (our bad exchange rates) to get as US & Europe.

Regards
Allan

[arti492]

I can give you the pic18f4685 for free, you have to pay for the shipment from Poland .

[alllanb]

arti492, on 26 December 2011 - 13:30, said:

I can give you the pic18f4685 for free, you have to pay for the shipment from Poland .

Thank you for the offer I have no idea what that would cost. And how I could pay you???

My intention is to test the midification of old organ for church using Sonic Cell for the sound.
I wanted to get midi merge with 13 note pedals for start using keyboard(channel 1) in to midi merge with pedals added to midi on channel 3.
I was going to use midi128 16F877 hex file if it is possible with 1 din module.

I am able to get 18F chips for about $8 if the concept is acceptable to organists, only demo at present I have 16F887 chips at hand.

Regards
Allan

This post has been edited by alllanb: 26 December 2011 - 18:11

[Antix]

A paypal account may be helpful

[alllanb]

Antix, on 01 January 2012 - 13:36, said:

A paypal account may be helpful

Thank You I do have but have not used very often.

I have bought a 18F4620 am busy with vero board test setup

[Jon Wilder]

Migration from an F877 to an F887 is pretty simple. The configuration fuses and the init routine should be all you have to change.

Differences between the two PICs -

F877/F877A - Writing to the ADCON1 SFR changes the analog/digital I/O modes for the ADC and PORT pins
F887 - Has 2 dedicated SFR's for controlling the analog input/digital I/O modes for each ADC/PORT pin (ANSEL and ANSELH). These registers reside in register bank 3 on the PIC

Even though the F887 has an on chip oscillator, it is not stable enough for the MIDI bit rate. With the on chip oscillator, there is anywhere from a 1-3% error per bit, which exceeds the allowable tolerance spec in the MIDI specification (translates to a 10-30% error per byte). From experience, I would periodically get framing errors when sending/receiving MIDI data while using the internal oscillator. For best results, use a crystal oscillator. You will have 0% error with a crystal oscillator.

The minimum xtal speed to use is 4MHz. You can use a 1MHz but you will have to run the UART in high speed BRG mode (TXSTA,BRGH = 1) and you would load SPBRG with the value of 0x01 in this scenario. Here are some BRG values for 31.25Kbps -

If TXSTA,BRGH = 0, then use -

4MHz - SPBRG = 0x01
8MHz - SPBRG = 0x03
12MHz - SPBRG = 0x05
16MHz - SPBRG = 0x07
20MHz - SPBRG = 0x09

If TXSTA,BRGH = 1, then use -

1MHz - SPBRG = 0x01
4MHz - SPBRG = 0x07
8MHz - SPBRG = 0x0F
12MHz - SPBRG = 0x17
16MHz - SPBRG = 0x1F
20MHz - SPBRG = 0x27

Configuration Word - I use this for the F887 -

;*************************************************************************************************
;*************************************************************************************************
;**												**
;**				Header Information						**
;**												**
;*************************************************************************************************
;*************************************************************************************************

		list		p=16F887, r=dec, w=-302
		include		<P16F887.INC>
		__config	_CONFIG1, _LVP_OFF & _FCMEN_OFF & _IESO_OFF & _BOREN_OFF & _PWRTE_ON & _WDT_OFF & _HS_OSC

;Debug Off (default)
;Low Voltage Programming Off
;Fail Safe Clock Monitor Off
;Internal External Switchover Mode off
;Brown Out Reset off
;Data Code Protect off (default)
;Program Code Protect off (default)
;RE3 is MCLRE (default)
;Power Up Timer on
;Watchdog Timer off
;Standard Xtal Oscillator

;If using xtal from 1-4MHz, replace FOSC_HS in the configuration word with FOSC_XT (standard crystal oscillator)

You don't have to play with _CONFIG2 unless you plan to use brown out reset or you want to write protect the program ROM space from being written to in code.

A basic init routine for a 16F887 running a 16MHz xtal, all ports in output mode and all ADC lines set up for digital I/O -

;*************************************************************************************************
;*************************************************************************************************
;**												**
;**				Initialization Routine						**
;**												**
;*************************************************************************************************
;*************************************************************************************************

		org		0x000			;reset vector
		goto		START

		org		0x004			;interrupt vector
;		goto		ISR			;uncomment this line if you plan to use interrupts

START		clrf		PORTA			;init port latches
		clrf		PORTB
		clrf		PORTC
		clrf		PORTD
		clrf		PORTE
		banksel		ANSEL			;select RAM bank 3
		clrf		ANSEL			;AN0 - AN7 digital I/O mode
		clrf		ANSELH			;AN8 - AN13 digital I/O mode
		banksel		TRISA			;select RAM bank 1
		clrf		TRISA			;PORTA all outputs
		clrf		TRISB			;PORTB all outputs
		movlw		b'11000000'		;RC0-RC5 outputs
		movwf		TRISC			;RC6 UART TX, RC7 UART RX
		clrf		TRISD			;PORTD all outputs
		clrf		TRISE			;PORTE all outputs

;UART init
	
		movlw		0x07			;bit rate = 31.25Kbps for MIDI
		movwf		SPBRG			;w/16MHz crystal
		movlw		b'00100000'		;asynchronous serial, enable UART tx
		movwf		TXSTA
		banksel		0			;select RAM bank 0
		movlw		b'10010000'		;enable serial port
		movwf		RCREG			;enable continuous rx

If you're coding in Hitech C and assuming you're using Hitech C v9.83 (the header file definitions seem to change from one Hitech C release to the next...not sure why), the same code would look like such (again using 16MHz xtal and all ports set to output) -

/*
**********************************************************************************
**********************************************************************************
**										**
**			Header Information					**
**										**
**********************************************************************************
**********************************************************************************
*/

/*
* Hitech C v9.83 - consult your Hitech C p16f887.h file for the correct config word
* mnemonics if using an older version of Hitech C
*/

#include <htc.h>

__CONFIG(LVP_OFF & FCMEN_OFF & IESO_OFF & BOREN_OFF & PWRTE_ON & WDTE_OFF & FOSC_HS);

/* 
* Debug Off (default)
* Low Voltage Programming Off
* Fail Safe Clock Monitor Off
* Internal External Switchover Mode off
* Brown Out Reset off
* Data Code Protect off (default)
* Program Code Protect off (default)
* RE3 is MCLRE (default)
* Power Up Timer on
* Watchdog Timer off
* Standard Xtal Oscillator

* If using xtal from 1-4MHz, replace FOSC_HS in the configuration word with FOSC_XT (standard crystal oscillator)

*/

/*
**********************************************************************************
**********************************************************************************
**										**
**			Interrupt Handler					**
**										**
**********************************************************************************
**********************************************************************************
*/

void interrupt isr(void)
{
	
	//place interrupt handler code here (if applicable)

}

/*
**********************************************************************************
**********************************************************************************
**										**
**			Main Code Block						**
**										**
**********************************************************************************
**********************************************************************************
*/

void main(void)
{

	PORTA = 0x00;		//init port latches prior to switching to output mode
	PORTB = 0x00;
	PORTC = 0x00;
	PORTD = 0x00;
	PORTE = 0x00;
	ANSEL = 0x00;		//AN0 - AN7 digital I/O mode
	ANSELH = 0x00;		//AN8 - AN13 digital I/O mode
	TRISA = 0x00;		//RA0 - RA5 all outputs
	TRISB = 0x00;		//RB0 - RB7 all outputs
	TRISC = 0b11000000;	//RC0 - RC5 outputs, RC6 UART TX, RC7 UART RX
	TRISD = 0x00;		//RD0 - RD7 all outputs
	TRISE = 0x00;		//RE0 - RE2 all outputs

	//UART initialization

	SPBRG = 0x07;		//31.25Kbps for MIDI w/16MHz xtal
	TXSTA = 0b00100000;	//enable asynchronous mode, enable transmit
	RCSTA = 0b10010000;	//enable serial port, enable continuous rx

	//main code goes here

}

Other than that, the rest of your 877A code should remain the same. Hope this helps.

This post has been edited by Jon Wilder: 26 January 2012 - 01:09