I am working on a simple emulation of an old PlayStation controller. I have
two switches sw1 and sw2 connected to ra0 and ra1 both are active high and
pulled down via 10k pulldowns. The two switches are mapped to "up" and
"down" bits of the first data byte. The protocol is just SPI with added ATT
and ACK lines.
The PlayStation did not respond, under inspection of the logic analyzer the
data line acts sporadic.

http://old.nabble.com/file/p31243196/2njepub.jpg=20

code:

	LIST	p=3D16F648a		;tell assembler what chip we are using
	#include "P16F648a.inc"		;include the defaults for the chip

	__config 0x3D18=09
=09


                       =20
	#define	sw1			PORTA,0
	#define	sw2			PORTA,1
	#define psx_dat		PORTB,5
	#define	psx_cmd		PORTB,1
	#define	psx_att		PORTB,2
	#define	psx_clk		PORTB,3
	#define	psx_ack		PORTB,4




	cblock 0x20
	bit_count	;for counting to 8 in spi loop
	temp_out	;regester to be shifted out spi
	temp_in		;regester to be shifted in spi
	psxbutton0=09
	psxbutton1
	endc


	org    0x00
	goto    Start



INTserv      org    0x04           =20



Start
Setup
	movlw	0x07
	movwf	CMCON ;comparitors off
   	banksel	TRISA	;select bank 1
	movlw	b'10000000'
	movwf	OPTION_REG	;pullups off
   	movlw 	b'11'	=09
   	movwf 	TRISA		;ra0 and one input
	movlw 	b'001110'	=09
   	movwf 	TRISB
	banksel	PORTA	;select bank 0
	movlw	0xff
	movwf	PORTB
	clrf	PORTA
	movlw	0xff
	movwf	psxbutton0
	movwf	psxbutton1



Detect
	btfsc	psx_att	;wait for att line to go low
	goto	$-1
Scan	;scan sw1 and sw2 and map them to "up" and "down" on the pad
	bsf	psxbutton0,6;preset button down
	btfsc	sw1		;skip if button is not pressed
	bcf	psxbutton0,6	;clear if it is pressed
	bsf	psxbutton0,4
	btfsc	sw2
	bcf	psxbutton0,4
=09
	movlw	0xff;idol
	call	PSX_SPI
	call	Ack
	movlw	0x41
	call	PSX_SPI
	call	Ack
	movlw	0x5a
	call	PSX_SPI
	call	Ack
	movfw	psxbutton0
	call	PSX_SPI
	call	Ack
	movfw	psxbutton1
	call	PSX_SPI
	goto	Detect=09


PSX_SPI					;sends contents of w LSB first over psx_dat returns psx_cmd in =
w=20
	movwf	temp_out
	movlw	0x08
	movwf	bit_count

Clk_in_out
	btfsc	psx_clk ;wait for line to fall
	goto	$-1
	rrf		temp_out;clock rotate byte into carry flag
	btfss	STATUS,C	;if low
	bcf		psx_dat		;set low
	btfsc	STATUS,C	;if high
	bsf		psx_dat		;set high
	btfss	psx_clk		;wait for clock to go high to sample psx_cmd
	goto	$-1
	bsf		STATUS,C	;preset carry flag
	btfss	psx_cmd		;if psx_cmd is high than skip
	bcf		STATUS,C	;if low clear carry bit
	rrf		temp_in		;roll carry bit into temp_in
	decfsz	bit_count	;eight counts yet?
	goto	Clk_in_out	;if not clock another bit
	movfw	temp_in		;else return
	bsf		psx_dat		;make sure data line is pulled high again
	return
=09
Ack
	bcf		psx_ack=09
	goto	$+1	;3us pause
	nop
	bsf		psx_ack
	return


	end



"When the PSX wants to read information from a controller it pulls that
devices ATT line low and issues a start command (0x01). The Controller Will
then reply with its ID (0x41=3DDigital, 0x23=3DNegCon, 0x73=3DAnalogue Red =
LED,
0x53=3DAnalogue Green LED). At the same time as the controller is sending t=
his
ID byte the PSX is transmitting 0x42 to request the data. Following this th=
e
COMMAND line goes idle and the controller transmits 0x5A to say "here comes
the data".
After this command initiation proccess the controller then sends all its
data bytes (in the case of a digital controller there is only two). After
the last byte is sent ATT will go high and the controller does not need to
ACK."=20

Thank you.
                 -Eric

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