Questions about sync polarity and about 25kHz monitors

[buttersoft]

I am in the middle updating, or using as a jumping off point, Gambaman's awesome Ultimate VGA-to-SCART code from this thread - https://forum.arcadecontrols.com/index.php/topic,160869.0/all.html

I'm looking to add a few features, and hoping the brains trust here can help with a couple of questions about monitors:

Q1. Does sync polarity matter? Right now the code only cares if they match. My monitors and TV's don't seem to care which way csync is delivered. Does anything out there need, for example, +ve hsync and -ve vsync? How about with csync? Does any board or video source output only mixed sync polarities?

Q2. Do mid-res 25kHz-nominal arcade monitors, or dual/tri-syncs in that band, only accept a very narrow hsync range around 24960Hz? I'm thinking of the model 2 boards here, but what else is out there?

Thanks!

[Zebidee]

Hi Butters. What exactly are you trying to do here?

Are you having problems adapting Gamba's sync logic code to work with a 25khz band signal?

I use your 15khz dongle a lot. I understand it is based on the same Gambaman's PIC as used for the Ultimate VGA-SCART. It seems to work just fine, generating Csync from any polarity of H+V sync input, including mixed polarities.

FWIW I believe that SDTV csync should always be negative (i.e. mostly high with negative pulses), even if there are monitors that accept any polarity.

If you follow my development on GreenAntz, you might notice that I've been working on similar stuff, like making csync from any input, from a more analog perspective. I've also been working on a 15khz "screening" circuit using analog timer and PLL chips. It will pass any signal within about 1k of 15khz but block any others. This could easily be adapted for 25khz, and indeed I've already been dreaming this circuit up in my head.

I'm also concurrently working on a csync circuit that accepts input of any or mixed H+V polarity, including csync itself, and feeds that into the 15khz screening circuit.

https://forum.arcadecontrols.com/index.php/topic,164245.msg1781705.html#msg1781705

We should probably compare notes.

[buttersoft]

No problems in syncing to 25kHz, it was more about what's out there that i would want to cater to. No point updating the code with a 25kHz band if it's not going to work for someone with a 25kHz monitor

I am embarrassed to admit i'm using AI to write the code, it's something i wasn't going to be able to do quickly. If at all TBH. And i've moved chipsets a few times, due to limited features and then lack of flash-mem space.

I haven't yet looked into accepting c-sync at TV levels, only at TTL for now. Happy to compare notes though

[Zebidee]

Thanks for your reply.

What tools/resources (e.g. hardware, software) are you using the flash the chips? How do you program them?

No bad thing using AI to help. It seems well-adapted to programming as it can automatically integrate obscure rules, syntax and formatting stuff that gets boring for humans.

I don't mind programming myself either and, "at a glance", what I saw of gambaman's original work seems fairly straightforward. The only thing holding me back from using PICs more is knowing how to get started. My questions are the dumb & specific ones, like what hard/soft tools do you use. I should probably stop asking and just look harder for myself. Or ask AI. I guess Youtube awaits too.

Instead, I ended up solving 15khz sync filtering (for GreenAntz) by using an analog frequency/tone-decoder approach. I used AI to help, but 90% of its suggestions were completely useless. That 10% was worthwhile though as it helped give me ideas to progress further.

I wasn't talking about TV-level csync vs TTL sync, I don't think I need that for my current projects. I was talking about TTL-level Csync input to a csync generating circuit (like your 15khz dongle, which is great at doing csync BTW, but does not accept csync as an input).

Anyway, thought "comparing notes" might help you with your own projects in this space.

I am embarrassed to admit i'm using AI to write the code, it's something i wasn't going to be able to do quickly. If at all TBH. And i've moved chipsets a few times, due to limited features and then lack of flash-mem space.

I am embarrassed to admit i'm using AI to write the code, it's something i wasn't going to be able to do quickly. If at all TBH. And i've moved chipsets a few times, due to limited features and then lack of flash-mem space.

[Oberdan2]

Thanks for your reply.

What tools/resources (e.g. hardware, software) are you using the flash the chips? How do you program them?

No bad thing using AI to help. It seems well-adapted to programming as it can automatically integrate obscure rules, syntax and formatting stuff that gets boring for humans.

I don't mind programming myself either and, "at a glance", what I saw of gambaman's original work seems fairly straightforward. The only thing holding me back from using PICs more is knowing how to get started. My questions are the dumb & specific ones, like what hard/soft tools do you use. I should probably stop asking and just look harder for myself. Or ask AI. I guess Youtube awaits too.

Instead, I ended up solving 15khz sync filtering (for GreenAntz) by using an analog frequency/tone-decoder approach. I used AI to help, but 90% of its suggestions were completely useless. That 10% was worthwhile though as it helped give me ideas to progress further.

I wasn't talking about TV-level csync vs TTL sync, I don't think I need that for my current projects. I was talking about TTL-level Csync input to a csync generating circuit (like your 15khz dongle, which is great at doing csync BTW, but does not accept csync as an input).

Anyway, thought "comparing notes" might help you with your own projects in this space.

I am embarrassed to admit i'm using AI to write the code, it's something i wasn't going to be able to do quickly. If at all TBH. And i've moved chipsets a few times, due to limited features and then lack of flash-mem space.

I am embarrassed to admit i'm using AI to write the code, it's something i wasn't going to be able to do quickly. If at all TBH. And i've moved chipsets a few times, due to limited features and then lack of flash-mem space.

These aren't silly questions; getting started with PICs can be confusing. I use a PICkit 5 with the MPLAB X IDE and MPLAB IPE. I connect the chip via ICSP, select the model, load the HEX file, and program it.

I also agree with you about AI: many suggestions aren't helpful, but some might give you the idea you need to move forward.

Now I understand the clarification about C-sync as a TTL input. Thanks for sharing your notes; I’m interested in learning more about your solution for GreenAntz, and I’m glad to hear that the adapter is working well.

[buttersoft]

I was using the same PIC16F18313 from Gambaman's original project, programmed via a Pickit3 clone using MPLAB IPE (the older versions are easier to use, the newer IDE is feature-complete but full of feature-creep too). But the PIC's are older, and couldn't do everything i want. I then moved to an ATTiny824, which is programmed via UPDI (three-pin programming via a CH341 serial adapter with power and ground, using a 1k resistor on the TX line, merged with the RX line and then connected to the ATTiny's UPDI pin. You can also get UPDI Friend adapters cheap, which are the same thing but packaged). I'm now onto an aVR32EB14, as the ATTiny ran out of it's 8kB of flash space for all the features i wanted to jam in, and wasn't fast enough either.

I plan to put together a big post once i'm done and ready to ship a few dongles out for testing, and i think it's going to be big, as i only want to write things out once

[Zebidee]

I plan to put together a big post once i'm done and ready to ship a few dongles out for testing, and i think it's going to be big, as i only want to write things out once

Exciting times! Looking forward to hearing more, but won't probe too much. Maybe we can do a swap?

Seems like you're fully opening the Pandora's Box of programmable ICs. Demanding newer and better It is an exciting area as there are all kinds of plug-n-play applications, as well as more customised designs. 8K was enough for a simple home computer in the early 1980's, and now you can get that on a single chip. Quite powerful.

Thanks for your advice about the Pickit and such. Yeah I looked online a while back and saw some negative reactions to the latest versions. I guess that is mostly people just complaining about change. Well, I won't have to worry about that.

I've already used a CH341a (two in fact) for re-programming TV EEPROMs. They are cheap and versatile.