Tapadjust: Vic-20 head alignment
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- Vic 20 Newbie
- Posts: 7
- Joined: Fri Jul 17, 2020 6:25 pm
Tapadjust: Vic-20 head alignment
Hi all.
I created Tapadjust, a head alignment program for the Vic-20. It is based on the Micro Head Align program for the C64. I created this for people who are having trouble loading tapes on a Vic-20. There are many programs like this on the C64, but not everybody who has a Vic also has a C64.
Maybe I shouldn't call it a "head alignment program", since the last thing to troubleshoot is the tape head. Tape load errors can be caused by deteriorated tapes, failing circuitry, dirty heads or rusty contacts. However, these sorts of programs can let you know if clean signals are being sent to the Vic-20. For example, one can start troubleshooting errors by comparing the outputs from Vice or a Tapuino, and a real Datassette.
Let me know what you think. This is my first machine language program and it runs on an unexpanded Vic-20. It's saved as a Basic program so that people who only have a Datassette can type it out and run it.
The attached zip file contains a D64, PRG and TXT file of the program.
Cheers
I created Tapadjust, a head alignment program for the Vic-20. It is based on the Micro Head Align program for the C64. I created this for people who are having trouble loading tapes on a Vic-20. There are many programs like this on the C64, but not everybody who has a Vic also has a C64.
Maybe I shouldn't call it a "head alignment program", since the last thing to troubleshoot is the tape head. Tape load errors can be caused by deteriorated tapes, failing circuitry, dirty heads or rusty contacts. However, these sorts of programs can let you know if clean signals are being sent to the Vic-20. For example, one can start troubleshooting errors by comparing the outputs from Vice or a Tapuino, and a real Datassette.
Let me know what you think. This is my first machine language program and it runs on an unexpanded Vic-20. It's saved as a Basic program so that people who only have a Datassette can type it out and run it.
The attached zip file contains a D64, PRG and TXT file of the program.
Cheers
- Attachments
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- tapadjust01.zip
- zip containing prg, d64 and txt file of program
- (5.03 KiB) Downloaded 107 times
- chysn
- Vic 20 Scientist
- Posts: 1205
- Joined: Tue Oct 22, 2019 12:36 pm
- Website: http://www.beigemaze.com
- Location: Michigan, USA
- Occupation: Software Dev Manager
Re: Tapadjust: Vic-20 head alignment
What about documentation? I'd like to check alignment for my original C1N. When I press play, it draws some lines and stuff on the screen, but what kind of information is this giving me?
VIC-20 Projects: wAx Assembler, TRBo: Turtle RescueBot, Helix Colony, Sub Med, Trolley Problem, Dungeon of Dance, ZEPTOPOLIS, MIDI KERNAL, The Archivist, Ed for Prophet-5
WIP: MIDIcast BASIC extension
he/him/his
WIP: MIDIcast BASIC extension
he/him/his
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- Vic 20 Newbie
- Posts: 7
- Joined: Fri Jul 17, 2020 6:25 pm
Re: Tapadjust: Vic-20 head alignment
Good question! I am working on that. There is sparse documentation for these programs even for the C64 versions of these programs.
I have some more information on my blog:
https://theokoulis.com/index.php/2020/1 ... he-vic-20/
I will add more info soon... I learned a lot about reading registers and flags on the Vic-20 so it is a good idea to document this for future reference.
More info to follow soon.
Thanks
I have some more information on my blog:
https://theokoulis.com/index.php/2020/1 ... he-vic-20/
I will add more info soon... I learned a lot about reading registers and flags on the Vic-20 so it is a good idea to document this for future reference.
More info to follow soon.
Thanks
- chysn
- Vic 20 Scientist
- Posts: 1205
- Joined: Tue Oct 22, 2019 12:36 pm
- Website: http://www.beigemaze.com
- Location: Michigan, USA
- Occupation: Software Dev Manager
Re: Tapadjust: Vic-20 head alignment
Thanks, that's great information!
I'm sure I have other things to address before I start messing with the azimuth, but this should be a nice diagnostic tool regardless of the cause, right?
My original (childhood) C2N works for some of my old tapes, but not as well as a newer C2N. But I've never degaussed my original, and I've hardly ever cleaned the head. I'll give it a bit of attention, maybe even recap it, and see if I can whip it back into shape. It's all pretty low-risk because my second one works great, and renders (relatively) straight lines with your tool.
I'm sure I have other things to address before I start messing with the azimuth, but this should be a nice diagnostic tool regardless of the cause, right?
My original (childhood) C2N works for some of my old tapes, but not as well as a newer C2N. But I've never degaussed my original, and I've hardly ever cleaned the head. I'll give it a bit of attention, maybe even recap it, and see if I can whip it back into shape. It's all pretty low-risk because my second one works great, and renders (relatively) straight lines with your tool.
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- Vic 20 Newbie
- Posts: 7
- Joined: Fri Jul 17, 2020 6:25 pm
Re: Tapadjust: Vic-20 head alignment
That's correct. You can use the program as a diagnostic program. If the output is showing straight clean lines, then bytes are being detected by the Vic-20. A scatter of points is an indication that something is wrong.
- orion70
- VICtalian
- Posts: 4343
- Joined: Thu Feb 02, 2006 4:45 am
- Location: Piacenza, Italy
- Occupation: Biologist
Re: Tapadjust: Vic-20 head alignment
Very simple and intuitive (well, once you know what's going on
) tool. Thanks for that. Judging from the pictures in your blog, I understand that it's a matter not only of "scattered points", but also of how thick the vertical lines are: the thinner, the better. Right?
![Smile :)](./images/smilies/icon_smile.gif)
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- Vic 20 Newbie
- Posts: 7
- Joined: Fri Jul 17, 2020 6:25 pm
Re: Tapadjust: Vic-20 head alignment
Thanks, glad you like it. I should really work on some documentation for the program (my actual work is keeping me busy these days... the nerve!!!)
Yes, it's not only a matter of scattering of points. I had a C2N that was so giving me so much trouble, and I really thought the tape head was misaligned. No matter the adjustment of the tape head, I was not able to consistently load from tape.
But then I used the program on: (1) Vice emulator, (2) another c2n that was giving me consistent loads, and (3) the troublesome c2n. I noticed that the lines were much thicker on the troublesome c2n. That got me to look at the electronics. I replaced the electrolytic capacitors, and cleaned out all the left-over crusty flux on my board. In addition, I tried out some of the suggested changes from this memo. That improved the signals, and after a little adjustment of the tape head I am now able to consistently load from tape.
Yes, it's not only a matter of scattering of points. I had a C2N that was so giving me so much trouble, and I really thought the tape head was misaligned. No matter the adjustment of the tape head, I was not able to consistently load from tape.
But then I used the program on: (1) Vice emulator, (2) another c2n that was giving me consistent loads, and (3) the troublesome c2n. I noticed that the lines were much thicker on the troublesome c2n. That got me to look at the electronics. I replaced the electrolytic capacitors, and cleaned out all the left-over crusty flux on my board. In addition, I tried out some of the suggested changes from this memo. That improved the signals, and after a little adjustment of the tape head I am now able to consistently load from tape.
Re: Tapadjust: Vic-20 head alignment
very nice tool.
I have a related issue, that is finding the right level when you playback WAV files from the PC to the real VIC (I do that via a car-cassette adapter). I find the volume level is rather critical. I was about to write a tool of my own for that purpose. My idea was to create an audio signal where a fixed 32 bit number is encoded and repeated over and over. The VIC20 could read such number and display on the screen the bit error rate, so that you adjust the playback volume for lowest BER. Perhaps that idea could be also used for head alignment?
I have a related issue, that is finding the right level when you playback WAV files from the PC to the real VIC (I do that via a car-cassette adapter). I find the volume level is rather critical. I was about to write a tool of my own for that purpose. My idea was to create an audio signal where a fixed 32 bit number is encoded and repeated over and over. The VIC20 could read such number and display on the screen the bit error rate, so that you adjust the playback volume for lowest BER. Perhaps that idea could be also used for head alignment?
Re: Tapadjust: Vic-20 head alignment
Wow, I've just noticed this useful tool!
Finally we have a tape head alignment program for the VIC!
Finally we have a tape head alignment program for the VIC!
Mega-Cart: the cartridge you plug in once and for all.
Re: Tapadjust: Vic-20 head alignment
yoyoregime wrote:I should really work on some documentation for the program
Since I found the program very useful, I've adapted it to work for any memory configuration and I've added instructions/troubleshooting taken from the yoyoregime's blog, it include also a screen output example of a noisy datassette and clean datassette.yoyoregime wrote:it runs on an unexpanded Vic-20
Also centered the screen output for both PAL/NTSC systems.
This is the patched yoyoregime code in assembler:
Code: Select all
ScreenAddrTop = $fb
ScreenAddrBottom = $fc
org $1D00 ; SYS7424
BLK1_patch = 1 ; 0 produce the original yoyoregime code, 1 the patched version
.1D00:
;tapadjust 0.1 original code
JSR $F894
JSR $E55F
SEI
LDY #$7F
STY $912E
LDA #$82
STA $912E
LDA $911C
AND #$F1
ORA #$0C
STA $911C
#if BLK1_patch == 0
LDA #$94
STA $9002
#else
; Set number of columns, works for all Vic Configurations (Unexpanded, 3K, 8K+)
lda $9002 ; #36866 bits 0-6 number of columns
; bits 7 serves as bit 9 of the 14-bit screen map address used by the VIC chip.
and #%10000000 ; clean bits 0-6
ora #%00010100 ; set bits 0-6 for 20 Columns
sta $9002 ;
INC $9000
INC $9000 ; Center X screen (Both PAL/NTSC)
ldx $288 ; Screen memory page ($1e for unexpanded/3k, $10 for 8k+)
stx ScreenAddrTop ; Top Screen memory page ($1e for unexpanded/3k, $10 for 8k+)
inx
stx ScreenAddrBottom ; Bottom Screen memory page ($1f for unexpanded/3k, $11 for 8k+)
#endif
.1D20:
LDA #$00
STA $D3
#if BLK1_patch == 0
LDA #$1E
#else
LDA ScreenAddrTop
#endif
STA $D4
.1D28:
LDA $9004
BPL .1D28
LDX #$1E
.1D2F:
LDY #$00
LDA #$02
.1D33:
INY
BIT $912D
BEQ .1D33
LDA $9121
LDA $900F
EOR #$02
STA $900F
DEX
CPX #$19
BCS .1D2F
CLC
TYA
LSR
LSR
TAY
LDA ($D3),Y
BCS .1D64
CMP #$20
BNE .1D5B
LDA #$61
JMP .1D73
.1D5B:
CMP #$E1
BNE .1D75
LDA #$A0
JMP .1D73
.1D64:
CMP #$20
BNE .1D6D
LDA #$E1
JMP .1D73
.1D6D:
CMP #$61
BNE .1D75
LDA #$A0
.1D73:
STA ($D3),Y
.1D75:
CPX #$00
BNE .1D2F
LDA #$0B
STA $900F
LDA $D3
CLC
ADC #$14
STA $D3
BCC .1D89
INC $D4
.1D89:
LDA $D4
#if BLK1_patch == 0
CMP #$1F
#else
CMP ScreenAddrBottom ; Screen memory page to check ($1f for unexpanded/3k, $11 for 8k+)
#endif
BEQ .1D93
BCS .1D99
BCC .1D28
.1D93:
LDA $D3
CMP #$CC
BCC .1D28
.1D99:
TSX
.1D9A:
JSR $EF96
DEX
BNE .1D9A
JSR $E55F
JMP .1D20
- Attachments
-
- tapadjust01b.zip
- (1.71 KiB) Downloaded 55 times
Mega-Cart: the cartridge you plug in once and for all.
- orion70
- VICtalian
- Posts: 4343
- Joined: Thu Feb 02, 2006 4:45 am
- Location: Piacenza, Italy
- Occupation: Biologist
Re: Tapadjust: Vic-20 head alignment
Very useful, thanks for having patched and provided instructions for it.