Two questions about backpack overlay

Chris B.

1. Phil Pilgrim wrote sometime previously:

The overlay stuff requires an external video source, such as a camera, before anything will appear on the screen.

In theory, could the code in prop_backpack_tv_overlay be modified to self-generate the sync pulse when external sync is not detected, while continuing to look for the external sync to change mode when external sync comes back? The purpose would be to have the display on the overlay still work even when the source video signal is missing.

My application is to throw weather info along the top and bottom of a surveillance cam image, and if the cam was dead, I still want the weather info on screen. (Not that a cam failure is likely to happen--so this question isn't a big deal.)

2. Has anyone incorporated graphics into the backpack overlay? I've made a display using my Demo board, now I opened up my backpack today naively thinking my program would port, that the genlock was just an added feature, not realizing until now the wiring and pasm firmware were completely different. I can use text only, but graphics on the overlay would look cool after spending a few hours laying up a wind direction indicator using arc and vector graphics.

Thanks.
Best regards,
Chris

Mike Green

1) Sure
2) I haven't seen it. There's no particular reason why you couldn't do it using the existing graphics object and TV bitmap driver as a starting point. I'm sure the existing overlay object is strictly text-based is because of memory constraints. A double-buffered bitmap driver plus graphics driver doesn't leave much memory for other code although you're not talking about a fancy program.

Duane Degn

Phil showed how to do some custom characters here.

Chris B.

Mike Green wrote: »

1) Sure

Thanks, Mike. I was worried it wasn't possible--figuring if it was possible, it would be default behavior already. The followup question is how? I can code in assembly but I don't know anything about analog video.

Duane, that tip is excellent. Now I'll look at doing bitmap graphics by re-writing the character defs.

Best regards,
Chris

Duane Degn

Chris B. wrote: »

Now I'll look at doing bitmap graphics by re-writing the character defs.

This has been on my todo list. I'd like to generate lines on the fly. If you get something working I hope you share it.

Chris B.

Duane Degn wrote: »

This has been on my todo list. I'd like to generate lines on the fly. If you get something working I hope you share it.

Duane, if I get it working, I'll post. Seems that Graphics.spin could be adapted to work in concert with _overlay2.spin by changing Graphics' plot and fill routines so that the bitmap is one bit per pixel instead of 2 and for proper indexing into the bitmap. But I might just get this project out the door with all text instead of tackling graphics.