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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Mon Feb 04, 2019 10:44 am 



Joined: 04 Feb 2019
Posts: 2
Is it possible to verify that the board was programmed correctly, before installation?

Context: I tried an USB Blaster clone for a while, gave up and found an JTAG-Arduino method, which required the SVF-file to be converted to XSVF.
The process "seems" to have worked, but I'd prefer to verify this before adding even more parts to the equation.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Mon Feb 04, 2019 5:24 pm 


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Joined: 15 Dec 2012
Posts: 605
Location: Finland
Digital Dragon wrote:
No I've checked, the serial number isn't the fake one. It's not a band of interference, more a glitch affecting specific graphics at a time. For instance in that video I posted, you can see it only ever affects the mountain in the background, so it's more like data corruption due to an issue with the clock line (or something) than video noise on the screen.
Are you using a shielded cable for MCLK_o? If not, it might be worth trying out as it has fixed stability issues in a few NES installations.

otj wrote:
I have a 1chip-01 SNES outfitted with a v1.2 dejitter board and Voultar's v.79 RGB bypass board. CSYNC_i is connected to the via that routes to pin 155 of the S-CPUN (and to pin 7 on the stock encoder). CSYNC_o is connected to the CS pad on the RGB bypass board. This all works fine, but does drop sync briefly once every few hours of gameplay. On a whim, I decided to check the sync line under load, and found that it's < 200mVpp, which I'm pretty sure is out of spec. Might explain the occasional sync drops.

I'm using a cable with no resistor on the sync line, so I think I'll short the TTL jumper on Voultar's board and slap a 330Ω resistor in the cable. That should be solidly in spec. I suppose I could also wire sync directly to the multi-out, but ~1.1Vpp seems a little high.
R9-R10 resistor divider values were updated in v1.3 PCB to produce nominal 300mV sync level with cables/mods that have 470ohm series resistor. ~1.1Vpp pure sync is also ok for video-level inputs (for reference, composite is 1Vpp) so directly soldering to multi-av should work too.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Tue Feb 05, 2019 5:24 am 


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Joined: 09 Jan 2018
Posts: 7
Location: Seattle, WA
marqs wrote:
R9-R10 resistor divider values were updated in v1.3 PCB to produce nominal 300mV sync level with cables/mods that have 470ohm series resistor. ~1.1Vpp pure sync is also ok for video-level inputs (for reference, composite is 1Vpp) so directly soldering to multi-av should work too.


Sounds great! Many thanks for the info, and thanks for designing such a great little board. I was unable to reach 5x without it. :D


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Tue Feb 05, 2019 8:06 pm 


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Joined: 01 Sep 2018
Posts: 51
Location: Wales
Hey Marqs, yes I'm using a coax. It seems I may have found what my issue is, it seems it was a big problem for Jason of gametechus. If anyone has similar symptoms to what I posted check out this thread.

https://shmups.system11.org/viewtopic.php?p=1297501#p1297501


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Fri Feb 08, 2019 8:39 pm 



Joined: 04 Feb 2019
Posts: 2
nosblod wrote:
Is it possible to verify that the board was programmed correctly, before installation?


Never mind, I got some extra time on my hands and actually installed the board. Works like a charm!
My unit had an SNS-CPU-GPM-01-board, but the guide for SNS-CPU-GPM-02 matched perfectly.

Thanks for all your great work marqs! <3

I did screw up and accidentally ripped the left copper pad away of R25, luckily I found the schematics and connected CSYNC_o to the lower pad of C46 instead.

One new question, would ATF1502AS-10AU44 be to slow for this? It seems easier to source in some countries. I ordered a bunch extra of the 7AU44's so I'm fine, just wondering if that should be an option for others. :)


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Feb 10, 2019 10:44 am 


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Joined: 01 Sep 2018
Posts: 51
Location: Wales
Ok so by removing Q1 on my AV Famicom I was able to get rid of the glitches. Turns out that shmups thread I linked to was the issue I was having. If anyone has any flickering pixels or 'snow' check that out, thanks for the help everyone :D

Also Viletim just posted on the NESRGB thread that a 2.0 NESRGB has been released as well as firmware for older NESRGB 1.X that includes the dejitter feature. So this may make the dejitter board redundant for NES and Famicoms. Kinda makes me wish I had waited, though I would have had to disconnect the clock anyway and would have lost my palette switch, so it's alright.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Feb 10, 2019 1:37 pm 


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Joined: 10 Feb 2019
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Location: London
I built the board myself, programmed it with a Raspberry Pi and installed it in my AV Famicom according to retromodwiki.com's instructions using a shielded wire. I only get grey screen when dejitter board is connected but the console is working perfectly fine using the stock crystal which I connected back for troubleshooting. I have an access to an oscilloscope and I saw that amplitude of a clock signal coming out of the dejitter board drops to around 2V pk-pk which is probably fine for the NESRGB and might be fine for the PPU but the CPU's M2 line is silent. Am I doing something wrong? Should I remove the voltage divider from the dejitter board?


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Thu Feb 14, 2019 4:00 pm 



Joined: 13 Mar 2011
Posts: 1032
Location: Toronto, Canada
FYI .. there's a new version of NESRGB with dejitter firmware.

If you have an NESRGB now, there's instructions on how to update a few components on the NESRGB to enable dejitter as well as new firmware to enable this feature.

Firmware location: https://etim.net.au/nesrgb/background_fault/
Update instructions: https://etim.net.au/nesrgb/background_f ... itter.html


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Feb 17, 2019 10:56 am 


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Joined: 21 Oct 2013
Posts: 683
Anyone in the USA selling assembled boards? Rather not have a wait ordering from the UK and no time to assemble myself.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Feb 17, 2019 12:26 pm 


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Joined: 15 Dec 2012
Posts: 605
Location: Finland
monster wrote:
I built the board myself, programmed it with a Raspberry Pi and installed it in my AV Famicom according to retromodwiki.com's instructions using a shielded wire. I only get grey screen when dejitter board is connected but the console is working perfectly fine using the stock crystal which I connected back for troubleshooting. I have an access to an oscilloscope and I saw that amplitude of a clock signal coming out of the dejitter board drops to around 2V pk-pk which is probably fine for the NESRGB and might be fine for the PPU but the CPU's M2 line is silent. Am I doing something wrong? Should I remove the voltage divider from the dejitter board?

2V is indeed way too low, it should be around 3-4V. Could you check the resistor values you've used and measure the output level when MCLK_o is not connected anywhere? Removing voltage divider altogether is not recommended since the clock line also drives NESRGB's CPLD which is not designed for 5v signal level.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Feb 17, 2019 4:48 pm 



Joined: 19 Jul 2017
Posts: 980
Pasky wrote:
Anyone in the USA selling assembled boards? Rather not have a wait ordering from the UK and no time to assemble myself.

If you're looking for a dejitter for the NES, the Tim Worthington's US distributor has NESRGB v2 boards in stock that have dejitter capability baked in, and there'll be a new firmware for 1.3/1.4 boards that includes it at the cost of palette selection.

If for SNES, I'm not aware of any. I'd make a post in the Wanted forum.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Feb 17, 2019 5:29 pm 


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Joined: 21 Oct 2013
Posts: 683
nmalinoski wrote:
Pasky wrote:
Anyone in the USA selling assembled boards? Rather not have a wait ordering from the UK and no time to assemble myself.

If you're looking for a dejitter for the NES, the Tim Worthington's US distributor has NESRGB v2 boards in stock that have dejitter capability baked in, and there'll be a new firmware for 1.3/1.4 boards that includes it at the cost of palette selection.

If for SNES, I'm not aware of any. I'd make a post in the Wanted forum.


Cool thanks.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Feb 17, 2019 10:26 pm 


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Joined: 10 Feb 2019
Posts: 2
Location: London
marqs wrote:
2V is indeed way too low, it should be around 3-4V. Could you check the resistor values you've used and measure the output level when MCLK_o is not connected anywhere? Removing voltage divider altogether is not recommended since the clock line also drives NESRGB's CPLD which is not designed for 5v signal level.


Voltage divider is as in BOM for ver. 1.2: 39/300 Ohm.
I measured the voltages with and without load and here's what I got:
Under load: GCLK_o: 3.36Vpk, MCLK_o: 1.5Vpk
No load: GCLK_o: 4.20Vpk, MCLK_o: 3.36Vpk


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Feb 17, 2019 11:48 pm 


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Joined: 02 Apr 2018
Posts: 22
Location: Arkansas
Pasky wrote:
Anyone in the USA selling assembled boards? Rather not have a wait ordering from the UK and no time to assemble myself.

I have a couple boards assembled right now that I could let go of. P.M. me if you are still looking.
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