Will a C64 light pen work on a Vic-20?

[necronom]

I have a C64 Trojan Light Pen and before I plug it into my Vic-20 to try out "Commodore Artist", I'd like to know I'm not going to damage it in any way.

Are all light pens compatible between the C64 and Vic-20, or do I need a Vic-20 one? The box says it's for the C64 and C128, but no mention of the Vic (possibly because the CAD-Master software wouldn't work).

[Mike]

There are no specific light pens for VIC-20s - your Trojan Light Pen equally well works with the VIC-20.

"Commodore Artist"

You might want to try out MINISKETCH.

[necronom]

Thanks. I tried it, but I'm guessing it's NTSC as the cursor is all over the place.

I can't get past the calibrate screen on MINISKETCH as I don't have a button on it and I couldn't find a key to act as the button.

[Mike]

Thanks. I tried it, but I'm guessing it's NTSC as the cursor is all over the place.

With "it" I presume you meant Commodore Artist?

Even if your version of CA is NTSC, that'd merely shift the display window to the top-left on PAL displays, but the lightpen still should work (sort of) and the cursor should not jump around uncontrollably.

Did you actually use a CRT with the light pen? A light pen won't work with flat screens (and neither, for that matter, with frame-doubling CRTs that output at 100 Hz or 120 Hz).

I can't get past the calibrate screen on MINISKETCH as I don't have a button on it and I couldn't find a key to act as the button.

MINISKETCH requires a light pen with trigger switch, sorry.

[necronom]

Yes, I did mean CA. Sorry for the confusion.
I think the screen was to the left when I loaded it, which is why I thought it must be something to do with the timing as it's expecting a 60Hz flash and not 50. I'm not 100% sure how it works, but I think it just counts time from the VBL to the flash it gets, so 60/50 would be different timings and it would think I'm in a different place and be out of sync jumping all over.
Yes, it's a CRT.
It was very tight to plug in my joystick extension, so it's possible it wasn't quite in fully. It was about to crack the plastic. I didn't want to force it in my actual Vic-20 port as it may damage it, or crack the solder if I have to push too hard. I have another extension, so I'll give that a go.

I though putting a key press in MINISKETCH would be a very easy thing to do so it works for all light pens.

Thanks for the help.

[Mike]

I thought it must be something to do with the timing as it's expecting a 60Hz flash and not 50. I'm not 100% sure how it works, but I think it just counts time from the VBL to the flash it gets, so 60/50 would be different timings and it would think I'm in a different place and be out of sync jumping all over.

The lightpen is a hardware function implemented in the video chip itself, and it works the same regardless whether on PAL or NTSC. The video chip knows where the electron beam is supposed to be and when the photo diode catches the light patch, that current position is latched into the lightpen registers.

I though putting a key press in MINISKETCH would be a very easy thing to do so it works for all light pens.

Maybe, but it takes time to re-open the project, make considerable thoughts how to incorporate the change without breaking other things, change the program, test it, change the documentation, re-upload, add another post in the respective thread. Time I don't have at the moment.

Sorry I can't be of more help this time.