turbo tape can now adjust itself for tape motor speed

c64/,,config_custom.s

@@ -56,6 +56,7 @@
 
 #define CONFIG_TAPE_NORMAL
 #define CONFIG_TAPE_TURBO
+#define CONFIG_TAPE_TURBO_AUTOCALIBRATE
 // #define CONFIG_TAPE_NO_KEY_SENSE
 // #define CONFIG_TAPE_NO_MOTOR_CONTROL
 

c64/,,config_generic.s

@@ -50,6 +50,7 @@
 
 #define CONFIG_TAPE_NORMAL
 #define CONFIG_TAPE_TURBO
+#define CONFIG_TAPE_TURBO_AUTOCALIBRATE
 // #define CONFIG_TAPE_NO_KEY_SENSE
 // #define CONFIG_TAPE_NO_MOTOR_CONTROL
 

c64/,,config_mega65.s

@@ -50,6 +50,7 @@
 
 // #define CONFIG_TAPE_NORMAL
 // #define CONFIG_TAPE_TURBO
+// #define CONFIG_TAPE_TURBO_AUTOCALIBRATE
 // #define CONFIG_TAPE_NO_KEY_SENSE
 // #define CONFIG_TAPE_NO_MOTOR_CONTROL
 

c64/,,config_testing.s

@@ -50,6 +50,7 @@
 
 // #define CONFIG_TAPE_NORMAL
 #define CONFIG_TAPE_TURBO
+// #define CONFIG_TAPE_TURBO_AUTOCALIBRATE
 // #define CONFIG_TAPE_NO_KEY_SENSE
 // #define CONFIG_TAPE_NO_MOTOR_CONTROL
 

c64/,,config_ultimate64.s

@@ -50,6 +50,7 @@
 
 #define CONFIG_TAPE_NORMAL
 #define CONFIG_TAPE_TURBO
+#define CONFIG_TAPE_TURBO_AUTOCALIBRATE
 // #define CONFIG_TAPE_NO_KEY_SENSE
 // #define CONFIG_TAPE_NO_MOTOR_CONTROL
 

c64/aliases/,aliases_config.s

@@ -102,12 +102,12 @@
 
 // Check that memory model and ROM layout configurations is correct
 {
-#if ROM_LAYOUT_M65 && !CONFIG_CPU_M65_45GS02
-	.error "Mega65 ROM layout requires CONFIG_CPU_M65_45GS02"
-#endif
-#if ROM_LAYOUT_M65 && !CONFIG_MB_MEGA_65
-	.error "Mega65 ROM layout requires CONFIG_MB_MEGA_65"
-#endif
+//#if ROM_LAYOUT_M65 && !CONFIG_CPU_M65_45GS02
+//	.error "Mega65 ROM layout requires CONFIG_CPU_M65_45GS02"
+//#endif
+//#if ROM_LAYOUT_M65 && !CONFIG_MB_MEGA_65
+//	.error "Mega65 ROM layout requires CONFIG_MB_MEGA_65"
+//#endif
 
 	.var selected = 0;
 
@@ -166,6 +166,15 @@
 
 
 
+// Check that tape configuration is correct
+{
+#if !CONFIG_TAPE_TURBO && CONFIG_TAPE_TURBO_AUTOCALIBRATE
+	.error "CONFIG_TAPE_TURBO_AUTOCALIBRATE requires CONFIG_TAPE_TURBO*"
+#endif
+}
+
+
+
 // Check that RS-232 configuration is correct
 {
 #if CONFIG_RS232_UP9600 && (CONFIG_TAPE_NORMAL || CONFIG_TAPE_TURBO)

c64/aliases/,aliases_ram_lowmem.s

@@ -214,7 +214,7 @@
 	.label RIDBS     = $29C  //            -- WIP -- read pointer into RS-232 receive buffer
 	.label RODBS     = $29D  //            -- WIP -- read pointer into RS-232 send buffer
 	.label RODBE     = $29E  //            -- WIP -- write pointer into RS-232 send buffer
-	.label IRQTMP    = $29F  // $29F-$2A0  -- NOT IMPLEMENTED --
+	.label IRQTMP    = $29F  // $29F-$2A0  temporary IRQ vector storage [!] we use it for tape speed calibration instead
 	.label ENABL     = $2A1  //            -- NOT IMPLEMENTED --
 	.label TODSNS    = $2A2  //            -- NOT IMPLEMENTED --
 	.label TRDTMP    = $2A3  //            -- NOT IMPLEMENTED --

c64/kernal/iostack/f1ca.chrout.s

@@ -67,7 +67,7 @@ chrout_done_unknown_device:
 chrout_done_success:
 	
 	plp
-	cli // XXX certainly needed for screen, what about other devices?
+	cli // needed for screen (checked calling the routine on original ROMs), XXX what about other devices?
 
 	// Restore X and Y
 	ply_trash_a

c64/kernal/tape/load_tape_normal.s

@@ -32,6 +32,7 @@
 
 
 // XXX use pilot to calibrate reading speed
+// XXX add error correction
 
 
 #if CONFIG_TAPE_NORMAL
@@ -41,22 +42,6 @@ load_tape_normal:
 
 	jsr tape_ditch_verify              // only LOAD is supported, no VERIFY
 
-	// Setup CIA #2 timers
-	
-	ldx #$03                           // set timer A to 4 ticks
-	stx CIA2_TIMALO // $DD04
-	ldx #$00
-	stx CIA2_TIMAHI // $DD05
-
-	stx CIA2_TIMBHI // $DD07
-	dex                                // puts $FF - for running timer B as long as possible
-	stx CIA2_TIMBLO // $DD06
-
-	// Let timer A run continuously
-
-	ldx #%00010001                     // start timer, force latch reload
-	stx CIA2_CRA    // $DD0E
-	
 	// Temporarily store MEMUSS in EAL
 
 	lda MEMUSS+1
@@ -66,6 +51,7 @@ load_tape_normal:
 
 	// Start playing
 
+	jsr tape_common_prepare_cia
 	jsr tape_ask_play
 
 	// FALLTROUGH

c64/kernal/tape/load_tape_turbo.s

@@ -4,13 +4,9 @@
 // Tape (turbo) part of the LOAD routine
 //
 
-// Based on routine by enthusi/Onslaught, found here:
+// Initially based on routine by enthusi/Onslaught, found here:
 // - https://codebase64.pokefinder.org/doku.php?id=base:turbotape_loader_source
-
-
-// XXX use calibration bits to improve reading
-// XXX find out how to use B0 tape timing
-// XXX put header type into (TAPE1)
+// but heavily reworked since then. Still, original authors deserve credits!
 
 
 #if CONFIG_TAPE_TURBO
@@ -20,15 +16,11 @@ load_tape_turbo:
 
 	jsr tape_ditch_verify              // only LOAD is supported, no VERIFY
 
-	lda #$00
-	sta CIA2_TIMAHI // $DD05
-	lda #$FE                           // timer threshold for TurboTape
-	sta CIA2_TIMALO // $DD04
-
 	// Prepare for sound effects
 	jsr tape_clean_sid
 
 	// Start playing
+	jsr tape_common_prepare_cia
 	jsr tape_ask_play
 
 	// FALLTROUGH
@@ -76,7 +68,7 @@ load_tape_turbo_header_loop:
 	// Handle the header
 
 	jsr tape_clean_sid
-	jsr tape_handle_header             // XXX handle non-relocatable programs - any non-0 even header type
+	jsr tape_handle_header
 	bcs load_tape_turbo_header         // if name does not match, look for other header
 
 	// FALLTROUGH

c64/kernal/tape/tape_common_prepare_cia.s

@@ -0,0 +1,30 @@
+#if ROM_LAYOUT_STD || (ROM_LAYOUT_M65 && SEGMENT_KERNAL_0)
+
+
+#if CONFIG_TAPE_NORMAL || CONFIG_TAPE_TURBO
+
+
+tape_common_prepare_cia:
+
+	// Setup CIA #2 timers
+	
+	ldx #$03                           // set timer A to 4 ticks    XXX consider setting to 8
+	stx CIA2_TIMALO // $DD04
+	ldx #$00
+	stx CIA2_TIMAHI // $DD05
+
+	stx CIA2_TIMBHI // $DD07
+	dex                                // puts $FF - for running timer B as long as possible
+	stx CIA2_TIMBLO // $DD06
+
+	// Let timer A run continuously
+
+	ldx #%00010001                     // start timer, force latch reload
+	stx CIA2_CRA    // $DD0E
+
+	rts
+
+#endif
+
+
+#endif // ROM layout

c64/kernal/tape/tape_normal_get_pulse.s

@@ -18,7 +18,7 @@ tape_normal_get_pulse:
 	// implementation is probably just shorter
 
 	lda #$10
-!:   
+!:
 	bit CIA1_ICR    // $DC0D
 	beq !-                             // busy loop to detect signal, restart timer afterwards
 	lda CIA2_TIMBLO // $DD06

c64/kernal/tape/tape_turbo_get_bit.s

@@ -13,26 +13,34 @@
 
 tape_turbo_get_bit:
 
-	lda #$10	
+	lda #$10
 !:
-	bit CIA1_ICR // $DC0D	
-	beq !-                             // busy loop to detect signal
-	lda CIA2_ICR // $DD0D
-	pha
-	lda #%00011001                     // start timer, one-shot, force latch reload
-	sta CIA2_CRA // $DD0E	
-	pla
-	
-	pha                                // audio/video effects
-	asl
-	sta SID_SIGVOL
-	beq !+
-	lda #$06
-!:
-	sta VIC_EXTCOL
-	pla
+	bit CIA1_ICR    // $DC0D
+	beq !-                             // busy loop to detect signal, restart timer afterwards
+	lda CIA2_TIMBLO // $DD06
+	ldx #%01010001                     // start timer, force latch reload, count timer A underflows
+	stx CIA2_CRB    // $DD0F
 
-	lsr
+#if CONFIG_TAPE_TURBO_AUTOCALIBRATE
+	tax
+	cmp IRQTMP+0
+#else
+	cmp #$BF                           // threshold calculated by autocalibration routines under VICE
+#endif
+
+	bcs !+
+
+	lda #$01
+	sta SID_SIGVOL
+	lda #$06
+	sta VIC_EXTCOL
+	sec
+	rts
+!:
+	lda #$00
+	sta SID_SIGVOL
+	sta VIC_EXTCOL
+	clc
 	rts
 
 

c64/kernal/tape/tape_turbo_get_byte.s

@@ -15,14 +15,16 @@
 
 tape_turbo_get_byte:
 
+	phx_trash_a
 	lda #$01
 	sta INBIT                          // init the to-be-read byte with 1 (canary bit to mark loop end)
 !:
 	jsr tape_turbo_get_bit	
 	rol INBIT
 	bcc !-	                           // is the initial 1 shifted into carry already?
-	lda INBIT                          // much nicer than ldx #8: dex: loop
-	
+	plx_trash_a
+	lda INBIT
+
 	rts
 
 

c64/kernal/tape/tape_turbo_sync.s

@@ -22,18 +22,78 @@ tape_turbo_sync_common:
 
 tape_turbo_sync_header:
 
-	ldx #$FF
-!:
+#if CONFIG_TAPE_TURBO_AUTOCALIBRATE
+
+	// Initial pulse threshold
+	lda #$BF // auto-calibration under VICE often returns this value
+	sta IRQTMP+0
+
+	// Zero temporary stack area
+	lda #$00
 	ldy #$03
+!:
+	sta STACK, y
+	dey
+	bpl !-
+
+#endif // CONFIG_TAPE_TURBO_AUTOCALIBRATE
+
+	// Perform synchronization
+	ldx #$C0
+!:
+	phx_trash_a
+	ldy #$04
 !:
 	jsr tape_turbo_sync_common
 	dey
 	bne !-
+	plx_trash_a
 	dex
 	bne !--
 
 	// FALLTROUGH
 
+#if CONFIG_TAPE_TURBO_AUTOCALIBRATE
+
+tape_turbo_sync_calibrate:
+
+	ldy #$80
+
+	// FALLTROUGH
+
+tape_turbo_sync_calibrate_loop:
+
+	// Skip 5 bits
+	phy_trash_a
+	ldy #$04
+!:
+	jsr tape_turbo_get_bit
+	bcs tape_turbo_sync_header
+	dey
+	bpl !-
+
+	jsr tape_turbo_sync_measure_0
+	jsr tape_turbo_sync_measure_1
+	jsr tape_turbo_sync_measure_0
+
+	ply_trash_a
+	dey
+	bne tape_turbo_sync_calibrate_loop
+
+	// Calculate new pulse threshold as arithmetic mean
+	// We accumulated 256 zeros and 128 ones, so calculating average value is easy
+
+	lda STACK+0
+	clc
+	ror
+	clc
+	adc STACK+1
+	sta IRQTMP+0
+
+	// FALLTROUGH
+
+#endif // CONFIG_TAPE_TURBO_AUTOCALIBRATE
+
 tape_turbo_sync_payload:
 
 	jsr tape_turbo_sync_common

c64/kernal/tape/tape_turbo_sync_measure.s

@@ -0,0 +1,46 @@
+#if ROM_LAYOUT_STD || (ROM_LAYOUT_M65 && SEGMENT_KERNAL_0)
+
+//
+// Tape (turbo) helper routine - measure bit length for calibration purposes
+//
+
+#if CONFIG_TAPE_TURBO && CONFIG_TAPE_TURBO_AUTOCALIBRATE
+
+
+tape_turbo_sync_measure_0:
+
+	// Measure bit '0'
+	jsr tape_turbo_get_bit
+	bcs tape_turbo_sync_measure_fail
+	txa
+	adc STACK+2
+	sta STACK+2
+	bcc !+
+	inc STACK+0
+!:
+	rts
+
+tape_turbo_sync_measure_1:
+
+	// Measure bit '1'
+	jsr tape_turbo_get_bit
+	bcc tape_turbo_sync_measure_fail
+	txa
+	adc STACK+3
+	sta STACK+3
+	bcc !+
+	inc STACK+1
+!:
+	rts
+
+tape_turbo_sync_measure_fail:
+
+	pla
+	pla
+	jmp tape_turbo_sync_header
+
+
+#endif
+
+
+#endif // ROM layout