FORN=8TO30:OPEN1,N,2:CLOSE1:PRINTN;ST:NEXT

#include <cbm.h>
#include <stdio.h>


char openFile(void){
	char openErr;
	if ( (openErr = cbm_k_open()) ){
		printf("Open failed: Return value = %d\n", openErr);	
	}
	return openErr;
}

void main(void){
	char drivecmd[] = "u0>\x09";
	char openErr;
	
	cbm_k_setlfs (15, 8,15);
	cbm_k_setnam (drivecmd);
	if ( !(openErr = openFile()) ){
		cbm_k_close(15);
		printf("Successfully changed device\n");
		
	}else{
		printf("Could not change device\n");
		cbm_k_close(15);
	
	}
}

OPEN 1,ID,15,"M-W"+CHR$(119)+CHR$(0)+CHR$(2)+CHR$(0)+CHR$(0):CLOSE 1 

        tightloop = 0; 1 might work better on 1541, 0 might work better on 1571

        !to "busoff.prg", cbm

        * = $0801

        !word 2048, 2017; link, line number
        !byte $9e; SYS
        !text "2064"
        !byte 0, 0, 0; end

        !text "+H!"

        lda #9   ; device number
        jsr listen

!if tightloop {
        ldx #0
datalo: lda atnlo,x
        jsr $ffa8; IECOUT
        inx
        cpx #atnloend - atnlo
        bne datalo
        jsr $ffae; UNLSTN

        lda $ae  ; FA
        jsr listen
        ldx #0
datahi: lda atnhi,x
        jsr $ffa8; IECOUT
        inx
        cpx #atnhiend - atnhi
        bne datahi
        jsr $ffae; UNLSTN

        lda $ae  ; FA
        jsr listen
}
        ldx #0
exec:   lda command,x
        jsr $ffa8; IECOUT
        inx
        cpx #endcommand - command
        bne exec
        jmp $ffae; UNLSTN

listen: ldx #0
        stx $90  ; STATUS
        sta $ae  ; FA
        jsr $ffb1; LISTEN
        lda #$6f ; open channel 15 (command/error channel)
        jsr $ff93; LSTNSA
        lda $90
        bmi error
        rts

error:  brk

command:
        !text "M-E"; memory-execute
        !word drivecode
!pseudopc $0205 {
drivecode:
    !if tightloop = 0 {
        ; the simple approach
        sei
        lda #$20
        sta $1801; 2 MHz on 1571
        lda #$00 ; ATNA cleared, CLK OUT low, DATA OUT low
        ldx #$10 ; ATNA set, CLK OUT low, DATA OUT low
--      bit $1800; wait for ATN IN high
        bpl --
        stx $1800; set ATNA
-       bit $1800; wait for ATN IN low
        bmi -
        sta $1800; clear ATNA
        bpl --   ; loop
    } else {
        ; the not-so-simple approach
        sei
        lda #$ff
        sta $1803; set all port bits as outputs
        lda #>$0300
        sta $1801
        lda #$7f
        sta $1802; set only ATN IN as input
        lda #$00 ; ATNA cleared, CLK OUT low, DATA OUT low
        ldx #$10 ; ATNA set, CLK OUT low, DATA OUT low
        sta $1800
        jmp ($1800)
    }
} 
endcommand:

!if tightloop {
atnlo:  !text "M-W"; memory-write
        !word $0300
        !byte $16
        jmp ($1800)
        !byte 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
        sta $1800
        jmp ($1800)
atnloend:

atnhi:  !text "M-W"; memory-write
        !word $0380
        !byte $13
        stx $1800
        jmp ($1800)
        !byte 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
        jmp ($1800)
atnhiend:
}