Deriving Pixel Clock Info From VGA Output - Page 1
Forum section: electronics / projects

author: starhawk
author_rank: Regular Contributor
timestamp: August 15, 2020, 02:53:57 am
content: OK, so I'm purchasing an LCD Panel that's very odd. Datasheet attached.Without disclosing too much, at least for the sake of brevity, I want to drive it with the VGA output from a particular thin client that I'm intimately familiar with -- a Wyse C-series aka Wyse Cx0 client -- running FreeDOS. The LCD Panel takes direct VGA input, albeit at 5vTTL levels, and is 1bpp amber monochrome. I'm pretty sure that I can tie the RGB lines together and use an extraordinarily weak pulldown (100R?) and a fairly sensitive transistor -- or a JFET Op-Amp, something like a TL082 but 5v single rail (suggestions welcome!) wired as a comparator -- so that if there's any voltage at all it will read as a logic '1' the way it should. HSYNC and VSYNC can be directly connected.But then there's the pixel clock line.That's missing on the VGA connector but necessary for the panel. It'd be present on a VGA card's VESA Feature Connector, from which the panel is designed to be driven -- but like all motherboard graphics chipsets, there's not a connector of that sort available here. Being a thin client, there's really not an opportunity to change that, either.So what I'm left wondering is, how can I derive the pixel clock from the RGB lines and thus the pixel data itself?

author: gcewing
author_rank: Regular Contributor
timestamp: August 15, 2020, 09:30:43 am
content: Sounds like a job for a phase-locked loop of some kind.

author: Ian.M
author_rank: Super Contributor
timestamp: August 15, 2020, 10:23:55 am
content: Yep. Maybe a 25.175MHz VCXO (with enough pull range to accommodate the oscillator tolerance of the VGA signal source), a divider chain to get the dot clock down to the H-sync frequency and a 74HC4046 PLL chip for its phase detectors to close the loop. I don't know what happens to the H-sync during V-sync. If it stops, you may need to gate the PLL loop filter during V-sync so it doesn't glitch the VCXO control voltage.

author: starhawk
author_rank: Regular Contributor
timestamp: August 15, 2020, 05:19:26 pm
content: I'm pretty sure it'd have to be 25.144 MHzPer datasheet -- 70Hz VSync; HSync fires 449x per VSync; Px Clock fires 800x per HSync.Check my math...?Also: any chance there's just the tiniest 'blip' where the RGB lines drop to 0v or otherwise level-shift in between each instance of px-data being output (dunno what to call that data, it's analog so not a 'bit')? or something like broadcast NTSC/PAL where there's a signal overlaid on another signal and one can be filtered out to get the other? I'd really prefer, if possible, to avoid a "generate the clocking externally and hope it matches" sort of solution because I can't imagine it doing anything but glitching like heck.How do VGA monitors do it? Like, the early 1990s fixed-resolution ones (I have one! Samsung CVL422. It's heavy...).

author: Ian.M
author_rank: Super Contributor
timestamp: August 15, 2020, 05:37:50 pm
content: They don't! Old-skool CRT monitors just swept the beam horizontally at a constant speed, without needing a dot clock, letting the pixel data fall where it may.

author: james_s
author_rank: Super Contributor
timestamp: August 15, 2020, 06:02:01 pm
content: That same approach may actually work acceptably well with the panel, just drive it with a clock of the correct frequency, most TFT panels with H/V/dotclock interfaces advance the line with every hsync pulse and reset the frame with every vsync pulse. The dot clock latches the video signal into the active pixel and advances the horizontal counter to the next pixel. If you just feed it an open loop clock of the right frequency you might get a bit of pixel noise but I'd wager you'll get a recognizable image, possibly even good enough to do the job. Easy enough to try.You'll also have the pixel clock available somewhere in the video interface circuitry so if you're able to modify the hardware you can feed that out on a spare pin.

author: MattHollands
author_rank: Frequent Contributor
timestamp: August 15, 2020, 07:06:01 pm
content: It's maybe a little overkill, but I've previously used the TVP7002 for digitising VGA video and it has the clock reconstruction circuitry built in. Obviously it has a lot of hardware you wouldn't use, but it would be simple.

author: MattHollands
author_rank: Frequent Contributor
timestamp: August 15, 2020, 07:09:01 pm
content: Quote from: james_s on August 15, 2020, 06:02:01 pmIf you drive it with arbitrary phase the image is going to look terrible. And it will drift out of phase with the video if it's not locked. And it will look different every time you start it up.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 15, 2020, 07:23:20 pm
content: Eh, depends whether it's counting exactly 799/800/801 pixels per row and so on, or if it overflows (which would be undesirable), or if HSYNC resets X to exactly 0 and increments Y, or... On a properly timed signal, none of these assumptions matter and any combination would work, but only the more robust cases (X keeps counting without overflowing and is reset by HSYNC, Y increment on HSYNC only) will be tolerant of other timings.And yeah if nothing else, if it's not phase coherent, you'll get weird rippling and jittering as logical pixels shift physical positions, and as indeterminate values (rising/falling edges) are latched in.You can see all of this on a typical LCD (VGA) monitor, one with the pixel clock adjustable from the OSD menu. As you adjust phase, there may be a sort of shear line that goes across the screen as you cross the pixel boundaries; set it exactly opposite (i.e., sampling in the middle of the stable period) and you're good.And they do it exactly by PLL from HSYNC, using standard VGA timings guessed from the H and V sync periods. They will usually be confused by nonstandard timings; you might get away with that on a CRT, but might simply get a blank "out of scan range" here, or you might get a partial display (or even a rolling picture..?).And yes, for converting VGA video to logic -- simply using a comparator will suffice. Something faster than LM393 is a good idea, MCP6561 perhaps, or one of those 9ns or less types that I forget the numbers of. VGA has a low signal level (0-1V, or is it 0-0.3V?, into 75 ohms -- don't omit the termination resistors!), so a threshold in the middle will do the job.You're even doing the same job; a comparator is simply a 1-bit ADC. If you happen to find an affordable converter chip for this (ADCs included), just use the high bit.One last trick: the video may end up delayed due to the comparator, and this will shift the data relative to the pixel clock's phase. The data can be resynchronized by passing it through a D-type flip-flop (e.g. 74LVC74; probably better to use something faster than 74HC in this case), but don't forget to also delay the H and V sync signals, which need to be delayed by the same single clock cycle. Or use chains of D-f/f's to delay multiple cycles as needed.Tim

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 15, 2020, 07:34:51 pm
content: What chip does the thin client use for graphics? There might be a way to get the pixel clock from it.

author: BrianHG
author_rank: Super Contributor
timestamp: August 15, 2020, 08:17:00 pm
content: Well, I now know any bottom end Altera FPGA can do it...See my code here:https://www.eevblog.com/forum/projects/modern-equivalent-of-74hc4046-pll/msg3151084/#msg3151084And see the Jitter quality response here: (Well, when measured on a 1054z with 2 channels on):https://www.eevblog.com/forum/projects/modern-equivalent-of-74hc4046-pll/msg3153558/#msg3153558As best we could tell, the regenerated H-Sync locked clock was within the predicted performance of +/-750ps.Regenerating a 25.175MHz clock should have an even better theoretical +/-620ps jitter performance.You can also use the FPGA to re-clock the data coming in, or even double scan the lines going out converting 640x480 to 1280x960. You can even drive digital LCD panels directly or even synthesize a HDMI/DVI signal.The only down side to my PLL is it will be expecting 1 video resolution from the source.

author: starhawk
author_rank: Regular Contributor
timestamp: August 15, 2020, 09:05:55 pm
content: @ all -- definitely thinking about the TVP7002, although it's going to be *ahem* "interesting" to set that up. I think I know enough about Arduino code that I can wire up a Pro Mini board to do the register config stuff, yikes... although... somewhere in my closet I have two items that may be of interest.One is one of those RGB converter boards for silly people who want a real 15kHz CRT in their arcade cabinets but don't mind driving it with a RasPi or a pile of slightly-outdated laptop guts (mind you, if it's good enough to run the first three entries in the MYST series of games just fine -- i.e. a base-level XP era machine -- it's not really "old" yet) running RetroCade. Like this -->https://www.ebay.com/itm/253407215602The other is one of these scan converters -->https://www.ebay.com/itm/360529627744Maybe one of them has a px-clock output somewhere that I can use...?@ BrianHG -- no FPGAs, please, I have a very low budget and I know absolutely jack squat about the things other than they are universally a small fortune in price. I know almost no programming, either, by the way -- I'm vaguely sort of conversational in an antiquated variant of MS BASIC that shipped with MS DOS 6.22, as well as its more professional counterpart of the era, and I sort of know how to translate that into earlier dialects such as what's on the Commodore 64 (I forget its proper name at the moment), and I can sort of read C and bash scripts. I read an article once on how COBOL is supposed to be written and it made a lot of sense but I never followed that up with anything after.@ NiHaoMike --It's an... *ugh* VIA VX855. One of the rarest single-chip chipset jobs by that Taiwanese silicon-wastage firm. The CPU is a VIA Eden (I'm pretty sure it's "Nehemiah" core, but it's a bit hard to tell with VIA chips!) running at 1GHz. VIA's Eden line is the fanless equivalent of the C7 line if I've got my story correct... basically it's the low-power side of their already low-power chips... either way, performance is roughly equivalent to a scared-****less Dell CPi on a hefty dose of meth and PCPMind you the Latitude CPi series was very much a Pentium II machine lol... if you were *very* crafty and *very* lucky with your RAM selection you could get it all the way to 512MB... I think? Might be only 256MB. Don't remember, it's been a while.I'm familiar with the Wyse C-series clients in particular because of this little bit of fun over here -->https://bugs.freedesktop.org/show_bug.cgi?id=91966I have to say I'm rather proud of that effort!...as for VIA...You know those horribly cheap Android tablets that you can get at pharmacies in the US for like $30 a pop and on eBay for a bit less, sans any sort of recognizable brand name...? The ones that are so horribly slow that they're almost unusable, at least until six or so months later when the battery (or some other equally-critical component) finally gives out and renders the whole thing unusable without repairs that are far too costly, relative to original purchase price (not to mention the usefulness, or rather lack thereof, of the device even when operational), to be justified...?VIA made the SoC, almost invariably. The early ones (Android 2.x/3.x days) used a 600MHz model overclocked nearly double... the heat dissipation was what always did in the battery, since as with any other electronic component, lots of heat over lots of time will kill a battery dead quite handily.VIAs x86 offerings are equally awful. I met a laptop in a Staples once that had sound issues right off the bat -- no, really, the drivers weren't working right in... I think this was the early Win7 days... so that only one side of the stereo speakers were working with a YouTube video, and this was the freaking in-store demonstration model for Pete's sakes! Soon as I saw that it had a VIA chipset with integrated audio I knew why.Their CPU designs date from a little-noticed effort in the late 1990s by semiconductor manufacturer IDT to enter the x86 CPU market. Super Socket 7 motherboards were kind of a thing at the time -- the very first Pentium II, a 66MHz part, had come out in May of that year, but it needed a Slot 1 board and such things were rather expensive upgrades at the time, especially given that the processor itself didn't come cheap! So boards that could take eg an AMD K5/K6/K6-II CPU in the near future but for now could trundle along with the existing Pentium I CPU (as they were retroactively termed, now that there were multiple generations) were rather understandably kind of a hot item.IDT came up with a rather interesting approach for what they eventually marketed as the IDT WinChip. They'd kind of seen this opportunity coming a few years earlier and had established a sort of subsidiary sort of a thing called Centaur Technology (Heaven only knows why) that came up with the design for the WinChip. The concept was rather like the much-later Transmeta Crusoe -- the chip's internals were a very simple RISC design based vaguely on the 486 but that wasn't strictly speaking compatible with either it or the Pentium designs, and (it's not explicitly stated anywhere, although I didn't look all that hard!) may not even have been x86 inside at all. Meanwhile, on top of that was a bit of logic that translated between whatever gibberish the core spoke, and the x86 instructions and such required to interface it with the outside world that expected something far more familiar. Its floating point performance was even more abysmal than Cyrix's offerings of the day -- which were so bad at math, they pretty well killed off the company! so at about the rate of a particularly hungover Fifties Guy with an unusually ill-kept mechanical adding-machine of his era, then, I suppose -- but floating-point operations weren't actually all that necessary back then (remember, the first-generation Pentium CPUs were really the first ones where being FPU-less really wasn't an option -- except for another niche chipmaker's offering, NexGen's Nx586 -- but since software couldn't assume everyone had a 586-class CPU, they had to code for FPU-less systems as a reasonable possibility) so it wasn't too much of a big deal.Unfortunately, when Super Socket 7 systems pretty well died out, IDT didn't feel like it was worth the monetary bother to keep that effort going, and Centaur Tech wound up on the corporate auction block. VIA was the winning bidder, and their designs even today are descended from the groundwork laid by the WinChip... which is why, although they hardly use any power, they also have hardly any performance! It's also why they're so cheap, and so common in designs where cost wins over processing power -- they simply aren't good enough to command prices above a 'fire-sale' sort of level. Of course, in a thin client, since the very idea is that it's basically a networked KVM extender for a server somewhere else tasked with the actual heavy lifting, and really no actual 'computing' properly happens on it at any given time (at least with the intended use case), that's not really an issue...It's also quite beneficial if one is at least a little handy with computers and needs something that can sort of run a 32bit Linux distro at about 2009 netbook speeds, but in desktop form for $50ish US -- which is very achievable if you play your cards right! Eeeeexcellent GrannyComp type material, in other words -- and the Wyse C-series in particular is about the size of a mass-market paperback. Get an old iPod hard drive (or a similarly-sized PATA SSD) and (maybe) a USB WiFi card and you really don't need much more other than the OS itself.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 15, 2020, 09:31:02 pm
content: Quote from: starhawk on August 15, 2020, 09:05:55 pmRaspberry Pi 4 is in the same price range and even after the emulation overhead, likely perform better. If the apps you have in mind could be recompiled for ARM, then a Pi Zero would be competitive.

author: starhawk
author_rank: Regular Contributor
timestamp: August 15, 2020, 11:58:16 pm
content: I already have the clientand there's no specific program in mind... to some extent it's a nostalgia box. More than that I'd really prefer not to say.

author: dmendesf
author_rank: Frequent Contributor
timestamp: August 16, 2020, 03:01:53 am
content: Look for vídeo PLLs like MK9173-15 that derive pixel clock from VSYNC / HSYNC

author: starhawk
author_rank: Regular Contributor
timestamp: August 16, 2020, 04:00:55 am
content: A pity the datasheet for that chip doesn't specify the exact output frequencies per input frequency... even a graph somewhere would've been nice :-/Suppose I could give it a try tho.

author: james_s
author_rank: Super Contributor
timestamp: August 16, 2020, 05:11:22 pm
content: Quote from: starhawk on August 15, 2020, 09:05:55 pmThose are for going the opposite way, driving a modern VGA monitor with the CGA/EGA analog output of arcade boards, I have one that I occasionally use on the bench for working on boards.

author: oPossum
author_rank: Super Contributor
timestamp: August 16, 2020, 05:27:31 pm
content: Quote from: starhawk on August 16, 2020, 04:00:55 amAn external divider sets the ratio as shown in figure 1.

author: starhawk
author_rank: Regular Contributor
timestamp: August 17, 2020, 06:02:33 am
content: @ james_s -- yes, but it has a VGA input... it's the older yellow PCB version, if that's any help. I wonder, since it has a VGA input and a VGA output, if it has a patch-into-able pixel clock output... IIRC the chip is a rectangular QFP job, rather than a BGA, although the pin pitch is so fine (as usual with such chips) that I will almost guaranteed short at least three or four pins together if I'm the one holding the iron (LOL... I have a few friends tho).Now if only I remembered the actual chip number lol... actually, I'm not sure I've ever even looked. Oops.@ oPossum -- what I meant was, there's no way to say *specifically from the datasheet* eg "an input of 12544 Hz will produce an output of 54769372 Hz on CLK1 and 72354988 Hz on CLK2". IMPORTANT: I don't have the datasheet open right now and haven't for a couple hours. (I saved it to local storage tho.) Those numbers therefore are straight out of my... uhm nevermindand very likely don't correspond even to what little *is* in the datasheet. Ingredients: absolutely 100% made of stinky bovine metabolic waste byproducts, watch your step lol.

author: oPossum
author_rank: Super Contributor
timestamp: August 17, 2020, 12:48:22 pm
content: The datasheet can't tell you what the ratio is because that is determined entirely by an external (not part of that chip) divider that is required to make a useful frequency multiplier.If you want 31.250 kHz from 25.000 Mhz that is an 800:1 ratio so you have to provide a divide by 800 circuit connected between one of the clock outputs and the phase detector input. Either CLK1 or CLK2 output can be used.

author: starhawk
author_rank: Regular Contributor
timestamp: August 18, 2020, 06:26:38 pm
content: @ oPossum -- ahhhhh gotcha. Somehow I missed that part.@ james_s + all -- update, it's the green-PCB version and the chip has a heatsink on top. Silkscreen doesn't ID it... anyone have info?@ all -- I also have a plasma display panel from a Compaq III that was unrepairable. Panel is marked Matsushita/Panasonic MD400F640PD5 -- integrated control PCB is Matsushita MD400F640BDT02 -- control chip appears to be T.I. SN751521AFT -- all are untraceable. The datasheet most sites have for an "SN751521" chip is actually for an SN75152 and is therefore entirely unrelated and irrelevant. FTR, if I'm interpreting those markings correctly, it's an SN75 series 1521A chip in the FT package -- "SN75" is in tiny text and "1521AFT" is in much larger bold text. If I knew the supply voltages (4 pin connector marked "0v" "+HV" "-LVCC" "-HV") and control/data protocols/interface and pinout (2x10 20pin latched IDC connector), I could use it instead.

author: Miti
author_rank: Super Contributor
timestamp: August 18, 2020, 07:02:10 pm
content: Quote from: dmendesf on August 16, 2020, 03:01:53 amHSync only, it can’t go that low to VSync frequencies. I tried it and is very noisy.Edit: My post is confusing. I tried the chip with HSync and it is very noisy.

author: starhawk
author_rank: Regular Contributor
timestamp: August 20, 2020, 09:05:08 pm
content: @Miti -- thanks for the note@all -- anyone know anything about that Compaq panel? or something similar that might act the same way? Also, a pal is sending me a Toshiba 3200 something-or-other -- 286 or 386 laptop, I think he said this one's a 286... it's got a plasma panel like the Compaq does. I don't have a part # for it offhand, but if anyone knows anything about those, I'd love to hear that as well.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 21, 2020, 03:07:34 am
content: VGA and LCD do not go well together.VGA is an analog standard that does not have "pixels", especially in horizontal direction.Converting a digital raster of your video card into a analog signal, then digitize it again (or analog post proecessing) to try to match the physical pixels on a LCD is a horrible process.Especially in the early days there were problems with this where pixels of the video card ended op somewhere between pixels of the LCD monitor. Sometimes it resulted in horizontal fuzzy ness of text, other times you had flickering display areas because the monitor could not decide where to put those pixels.Complete small 14" vga LCD monitors are almost free second hand.Bare LCD panels with a PCB that converts a VGA signal to something the LCD can manage can also be bought for reasonable prices (Especially for low resolution monitors).So my guess is this is not really worth pursuing to diy.

author: starhawk
author_rank: Regular Contributor
timestamp: August 21, 2020, 05:39:19 am
content: @ Doctorandus_P -- there is a datasheet attached to the first post of this thread. I would appreciate it if you would read that datasheet, as doing so (I would politely recommend paying particular attention to the timing diagrams and protocol/interface information within) will clear up some things that it sounds like you are incidentally misunderstanding by way of not having read up.That of course assumes you are referring to the original display panel and not the ones from the Compaq or Toshiba, as mentioned -- in which case I'll note that I'm no stranger to a soldering iron, and that while I'm well aware of easier solutions here, for various complicated reasons that I'd really prefer not to go into, they do not suit me for this project... and that, further, if I was not interested in at least evaluating the difficulty of homebrewing a controller board for one or both of those displays, I would not be asking about how to do so. While I would've preferred, simply for the sake of expediency, to be able to nab one on eBay, that doesn't seem to be possible right now, as none are listed AFAICT -- and I'm okay with that, but I'd like to see if I can work out a way to interface with it despite that.

author: starhawk
author_rank: Regular Contributor
timestamp: August 21, 2020, 03:55:19 pm
content: Hey guys... I'm an idiot, lol.Got the display today... ohhh boy. That datasheet in my first post? Same part #, different company. The display is a Planar Systems model -- I'd figured that since they shared a part number, they would be identical...Nope.The display *actually* addresses like a DSTN panel or an old EL LCD like those GRiD laptops had, back in the day. I know *exactly* how I can run it, if I can find a similarly low-end thin client board with a 32bit PCI slot... the German restaurant equipment company Wincor Nixdorf makes a PCI video card for their Point-Of-Sale terminals that outputs the correct signaling, and I can get it on eBay for $25ish US. Of course, the mildly annoying thing is, it uses a 26pin "Micro Centronics" connector that eBay *doesn't* have... but I bet Mouser does. (I haven't actually looked yet. I probably should go do that, lol...)New -- *correct!* -- datasheet attached. (There are several different sub-models / revisions covered by this datasheet-- mine is an EL640.400-CE4.) Still hoping for info on the Compaq or Toshiba displays -- especially the Compaq one!

author: oPossum
author_rank: Super Contributor
timestamp: August 21, 2020, 04:31:28 pm
content: Planar, FinLux and Beneq are all the same company.Planar purchased FinLux in 1991. Beneq purchaed the EL division of Planar/FinLux in 2012.There where several versions of the 640x400 panel. Some where literally VGA and some where 4 bit 'TTL'. I think they also made a bi-color version.I have several smaller Planar EL displays that I drive with a MCU (using SPI/QSPI) or FPGA.

author: starhawk
author_rank: Regular Contributor
timestamp: August 21, 2020, 06:34:55 pm
content: @ oPossum -- good to knowstill haven't checked Mouser for that connector. Since I tend to have to be a ridiculously cheap bastard (plz don't ask... just know that my income is less than $1500/mo and it's not something I can easily change RN), does anyone know of an eBay listing for the things? 26pin Micro Centronics, male, with solder connections rather than crimp-type connections -- I have only awful ways (i.e. needlenose pliers) of doing thkse up, and proper crimpers are always insanely expensive.EDIT: hit 'post' too soon lol. For clarity, I'd look myself but I'm actually about to go into an appointment with my apartment complex manager for some minor paperwork stuff and I'm a bit late already...EDIT2: appointment was over about 90min ago... and, found that connector. Best part, whst I found was a whole cable! I'll buy it, and the card, next month. I'mma go see what my options are for PCI-capable thin clients...EDIT3: typo fix >_< @ phone kbd -- you had ONE job...!

author: starhawk
author_rank: Regular Contributor
timestamp: August 23, 2020, 04:10:58 pm
content: So the box with the Toshiba laptop showed up yesterday. Toshiba 3100e.Flat panel is marked, rather notably, as a Matsushita Panasonic MD400F640PD6 -- in other words, a very close relative of the one from the Compaq III! -- with an *extremely* different controller card, marked as a Matsushita M400F640BDT05. This one has *three* connectors -- the supply connector, five pins although two are 'key' pins and so there's only three positions populated; and a pair of connectors for the signalling. Thankfully Toshiba, in that era, put all their pinouts/etc in the manual! While the motherboard-side connector is the only one given a pinout, deriving the panel pinout is a simple matter of a bit of time with a multimeter set on continuity......here's the new wrinkle, though (since, after all, knowing me, there was always going to be that) -- *this* panel uses a similar but very slightly different (in an important way!) protocol from the DSTN LCD style panels I've seen before, which use the protocol borrowed from such LCDs where the panel is split logically into two CGA-resolution screens halfway down, and so the PC has to send both a given line, and its counterpart 200 lines down, at once. *This* panel still does 1bpp, 4px at a time -- i.e., monochrome on/off like a Compact Mac, but sending four pixels in a lump per pixel clock -- but it's not split! You send *exactly* 4px to it, not 4px as well as another 4px 200 lines down, *just* 4px.How can I easily (ish) drive that from something modern? I don't mind a microcontroller/etc solution as long as it works...EDIT: for clarity, that Toshiba has an internal power supply and takes a 120vAC IEC cable supply input like a regular desktop PC! Since its PSU is (back-of-the-envelope) good for *at least* 5vDC 6a and 12vDC 2a, I can easily run something like a Wyse C-series motherboard (which tops off at 12v 0.75a ish -- full load never breaks 9w!) as long as I don't need a PCI card. If I *do* need a PCI card... probably my best bet would be an HP t5720, but that's going to be pushing the PSU's 12v rail a bit hard -- it tends to need a 12vDC 2a supply just to get to a desktop... I don't know the PSU's actual full ratings; the Toshiba manual gives the supply ratings needed to run everything BUT the drives, and I don't have the original floppy drive so I don't know quite how power-hungry it was. The HDD is a Conner CP-3022. Typical floppy drives of the era, as near as I can tell, when added to that Conner drive, need enough current at spin-up that, on startup, the machine will pull at least 2a on the 12vDC rail... I assume the PSU is designed well enough that such a draw would be sustainable, but I don't even really know that. I'd have to do some tests.

author: starhawk
author_rank: Regular Contributor
timestamp: August 25, 2020, 01:06:42 am
content: Forgive me for the remark, please, but if I wanted to talk to myself, I'd just do it -- not post here.(Not angry, just a lil frustrated...)I really would like to use the Toshiba's plasma screen -- as detailed in the last post -- or, better, I think I can put its control board on the panel for the Compaq III, which I'd *really* like to do, because although the visible and active areas of both screens are the same, the Toshiba's is physically larger, and I have an awesome idea for the (dead, and impractical to revive) Compaq III I pulled that screen from, but I want to keep it looking (externally) as close to stock as possible while doing that.I'd like, ideally, to use this PCI card (https://www.ebay.com/itm/311823415611) to drive that panel -- it's the Wincor Nixdorf one I'd mentioned before. I also found this (http://www.csksoft.net/blog/post/el_and_plasma_disp.html-- Chinese, use Google Translate plz) and this (https://hackaday.io/project/160738-cstron-cstn-lcd-monitor)......but all of those potential solutions have issues in the wayThe info I have on that PCI card (a single PDF, attached) indicates that it's designed for the "split screen" (DSTN) type interface, which this screen controller doesn't do. The Chinese dude hasn't updated his blog in forever, although I suppose it's possible he's contactable by email (I didn't check, it didn't seem worth even that much effort, lol!) and the STM32 code for the board he shows is not posted anywhere on that page (or, quite likely, that site). The Hackaday dude, I've put up a note for him, but he hasn't done anything in a year or more, and *his* efforts also only work with DSTN type interfaces -- and I know barely anything about FPGAs to begin with, which doesn't help, especially since his is unobtainium.Any help would be deeply appreciated.

author: helius
author_rank: Super Contributor
timestamp: August 25, 2020, 06:43:23 am
content: Thanks for helping to drive up the price of vintage computers by hacking them to bits in ways that will never work. Have you considered a lucrative future as a museum vandal?

author: starhawk
author_rank: Regular Contributor
timestamp: August 25, 2020, 04:36:52 pm
content: Have you nothing better to do than insult people in situations you very clearly are largely ignorant of...?I should probably report you for trolling, but I will give you the benefit of the doubt to start with, and we'll see where this goes.I have a friend who lives in an adjacent state, who has a job that means he has money for whatever hobbies he wants. He collects and trades in this stuff. I came to know him through the actions of another friend of mine, although that part is not important. The fellow has been literally *giving* me this stuff for the most part -- "for the most part" because the first exchange, which was exactly that, was a trade -- I gave him two computers he wanted from my collection, and he in turn gave me some equipment of his.I received a Panasonic HHC ("Hand Held Computer"), a system I'd been very interested in for a very long time, and a *pair* of Compaq IIIs. One mostly works and is awaiting a full restoration; the other was destined to forever be a parts machine, at best.The mostly-working one almost-worked better after a keyboard swap with the parts box, which is also missing both of its drives, as well as the caddy they go into -- a bit like a modern laptop, the Compaq III has a removable drive module, essentially, a frame that the floppy (and HDD, if you want one -- it could come with one floppy and one HDD, or two floppies, and it can run both 5.25" and 3.5" disks, although there are a few quirks to the various configs) drives attached to, which then fits into a much larger cage that's a bit more like a desktop drive bay setup. That one also now has (after the swap) a very dead keyboard, and possibly other issues. I haven't investigated, because the way it's designed, it needs very unusual drives -- the working one has a 5.25" floppy that is, by necessity, so short it's almost square, and a 42meg (IIRC) hard drive that looks for all the world like an MFM drive someone shrank to 3.5" size and managed to make work with an IDE controller card strapped on haphazardly. I've mucked around with computers old and new since at least age 10 (in the mid-1990s) and I've never seen anything like it -- and I'm 34 now.The almost-working Compaq III needs a few afternoons of attention still -- the design is such that the BIOS settings are kept in a battery-backed RAM / RTC hybrid chip, a Dallas Semi DS1287. (One of the two has a DS1287+; I forget which one right now... doesn't really matter, tho.) The battery in that chip of course has long since expired, and without it, one must run the BIOS setup application -- which for some strange reason, Compaq insisted on leaving out of the BIOS ROM image! The original purchaser received (I suppose) a 360k 5.25" "Diagnostics Disk" with their computer, and it has that program, amongst others, on it... I have that disk, but only as a disk image, and because none of my other working computers have an internal 5.25" drive, I've had to do some cobbling-together to get an external one working (it's very doable, if you know enough about the systems of the era...). I haven't had the chance to test that yet, or to make the mod to the DS1287 that will fix it -- there were a couple of DS128x chips, and one of them (DS1285 IIRC) was designed to have two extra pins sticking out (Dallas Semi generally cut off unused pins internally on their chips) for an external battery connection (it had no internal one) and it is a fairly well-known hack within the retrocomputing community that one can carefully scrape away the outer shell of DS1287 chips and their close variants to expose the internal pins, cut off in those chips, where they'd show in a DS1285, and solder eg a CR2032-on-leads modern laptop cell onto those pins, resulting in a DS1287 that has a functional battery again if all goes well. Sure it's delicate, but there are several old systems that just won't accept the modern descendents of those old battery backed RTC-RAM chips, however similar such descendents might be.So at this point, restoration of the almost-working Compaq III involves making that hack-repair to the DS1287 chip onboard, then making and using the "Diagnostics Disk" floppy in physical form, and then establishing whether or not the original HDD's magnetics are intact enough to boot an OS if there even is one still resident on there -- which is a matter not doable by modern means, because this drive predates the era where hard drives have universal ways of telling computers how to set them up -- this drive absolutely must be configured manually, and such devices will never work with USB IDE adapters of any sort. You *have* to use an old system with a BIOS that has the ability to set cylinder/head/sector/etc settings manually or the drive will be inaccessible. Probably I will swap it for a CF card in an adapter, or at least a sub-504meg platter drive (which would be likely necessary; I have an early-1990s laptop, the system I'll be using to make that "Diagnostics Disk", actually, that has that capacity limit -- if you look up the limits of the original ATA specification, before it was even called IDE, you'll find out why... Wiki has an article that covers it) as the chances that those platters still hold a magnetic field of sufficient strength are unfortunately quite low... they simply weren't meant for a nearly 35-year service life; the fact that the drive even powers up at this point is something of a minor technological miracle.It's the parts machine, though, that I want to operate on with the discussion in this thread... although the phrase "operate on" is itself a bit grand as the machine was not even shipped assembled. Its motherboard and the separate special daughtercard that runs the plasma panel (which has an untraceable chip at its heart) were outside the case, as was the steel motherboard shield. The back cover (which goes over the motherboard) is in pretty bad shape, at least half the screws are missing, etc. I never tested its power supply (the almost-working one has been successfully powered-on at least twice) but I wouldn't expect much. Repairing that system to functionality is essentially impossible -- even simply replacing its 5.25" drive is at best unfeasible, to the standards I have (which it sounds, at least to me, like we actually share) -- even ignoring the fact that the caddy is entirely unobtanium at this point, I'd have to fabricate a replica, which is *quite* well beyond my abilities! -- the drive itself is also unobtanium -- as I said before, I've never seen such a short 5.25" drive anywhere else, and longer drives absolutely will not fit, simply as a matter of physical constraints.Given that, I'd at least like to give it a semi-stock *appearance* that is also functional, and that's what I'm trying to work out here, although that idea itself came out of a different project which was the original genesis of this thread (more on that in a moment). I can fit a physically-small modernish motherboard (from eg an HP thin client with a 32bit low-power VIA/etc processor) and a PCI card in the old motherboard bay with ease, and I know from past experiences with the WYSE C-series clients (most notably, turning one into a rather improvised Win95 nostalgia-box for a friend who had fond memories of a particular and very odd game that would not run on anything later, including Win98!) that such machines usually take quite nicely to FreeDOS and run at about the speed of a high-end 486 box after such an install. The rest is simply a matter of power supplies and peripherals.The *original* project involves another website, primarily a blog but it's got a community around it. I know most Web forums tend to have "we don't spread our stuff to other communities" policies so I'll keep this as simple as I can. The site is called "Hackaday" and is nominally an eclectic tech blog with an enthusiastic following, although in some ways it's gotten (IMO) a bit big for its trousers. I'd prefer to mostly leave that bit unexplained, in respect of both Hackaday and its community, and the policy I mentioned a moment ago... it's irrelevant to the project, anyways. The idea came out of the fact that a rather large number of recent(ish) blog posts, proportionally speaking, specifically ones involving projects from within the Hackaday community (for which the blog now has a section with a slightly different domain -- Hackadaycom is the blog; Hackadayio is the community/projects section), have featured "cyberdeck" style portable systems. I fully admit I've already contributed at least two articles to that pile since it began in earnest, about a year or so ago. That said, being an artist as well as a nerd, and knowing that the genesis of the term "cyberdeck" and the concepts around the form factor, to the extent a specific form factor can really be said to exist in any even semi-official sense (and even *that* is very much /de facto/ rather than /de jour/, having arisen far more out of the cyberpunk fan-community's efforts to make their own, than any description in a narrative work of the genre AFAIK/CT) -- I want to design and build a cyberdeck that is as 80s-authentic as I can manage without going absolutely nuts. I would prefer at this time to avoid providing specific build details, as currently (unless there's a build I'm unaware of -- not impossible, but unlikely, as I've done plenty of research) I'm the only one really pursuing such an endeavor, and I'd really like to be the first to do that, but a period-accurate display is an important part of that to me. While I could go with a 5" (ish) CRT display, and I have a relatively easy and cheap way to do that (an old Magnavox portable TV last owned by a now-deceased relative of my father's in-laws), the similar displays of the era were *far* sharper and more crisp -- this thing is a blurry mess, at best, in comparison! I also have an odd device (it's a fairly old example of what's typically called an HMI -- "Human Machine Interface" -- basically an intelligent remote display and serial terminal for a PLC driving factory equipment) with an EL LCD panel, a Sharp LJ64H034, but that also is operable equipment that I'd prefer to leave intact, and both identical and similar panels are extremely expensive -- I simply can't afford one right now.So there's your response. I hope you will receive it and reply in a far less abrasive and aggressive fashion than your first post in this thread.

author: starhawk
author_rank: Regular Contributor
timestamp: August 26, 2020, 05:20:08 pm
content: No further useful/helpful responses...? :-/

author: starhawk
author_rank: Regular Contributor
timestamp: August 26, 2020, 08:22:20 pm
content: Also...Don't ever tell me that something's impossible. I don't believe in "impossible" except in very limited special cases (eg trying to violate the laws of physics, etc) -- I've seen it done too many times. Show me a man who believes his dreams are impossible, and I'll show you a man who's been made to give up on himself because he's convinced that his dreams are too expensive and impractical, that they are not worth the effort. I will also show you a man who's been lied to. Never give up on yourself or your dreams, however expensive and/or impractical they may be -- they, and you, are absolutely worth it, simply by force of existence.Case in point... you know how like literally every electronics textbook ever will tell you that you can't create a Boolean inverter (NOT-gate) with diode-resistor logic? There's a guy, semi-local to me (we've met!), who's disproved it --https://hackaday.io/project/161669-light-logic-hic-svnt-draconesOne example of many.On a lesser scale... I build pretty computers out of literally cr*p in a bunch of bags and boxes in my closet. Junk just kind of finds me... might as well use it if it's gonna show up at random like that. I built a steampunk portable computer (and I'm working on a more traditional, modern-style cyberdeck at the moment) out of a jewelry box lid, an old copier drum from heaven-only-knowscom (lol!), Walmart angle brackets, and whatever computer parts I could get on eBay or scrounge from what I had on hand. Worked pretty good, need to do a new install of Mint tho, because I was an idiot with WINE... and then wound up dealing with several Ubuntu-based distros that didn't like the idea of a 32bit UEFI on a 64bit box. Go figure. Take a look, though, I think I can confidently say you'll not be disappointed --https://hackaday.io/project/164620-the-homebrew-steampunk-laptop-v2

author: starhawk
author_rank: Regular Contributor
timestamp: August 27, 2020, 11:02:40 pm
content: I'm afraid we have to have a little talk, here... I was hoping it wouldn't get to this point, but here we are.I have a very strict policy about exchanges of information and assistance that comes into play at this point... if a community refuses to even attempt to give adequate such assistance (for example, by ignoring several posts of mine in a row after a post from another member that is an obviously negative or trolling post, garnering the nasty response it absolutely deserves, as such), or outright refuses to help at all*, then, subsequent to my post regarding the fact that I'm being forced to move on, I do not share with that forum any further information towards that goal, especially if it's found elsewhere. It is *extremely* hypocritical for a group of people to refuse assistance, but then -- having created circumstances where I either have to expend a great deal of extra effort to accomplish my goal, or decide that my energy is better spent elsewhere for the time being (as you might gather from the previous post, I strongly dislike having to shelve a project, even in the best of such environments) -- come back to me with the demand that I share what I got from that extra work or be banned. I do not tolerate hypocrisy in others, and, as such, I keep myself from it as well. There are a surprising number of forums that do not understand this, and my response to them is very simple and very clear --If you wanted me to help you, you should've helped me. You had the opportunity, and you declined it, and thus the result is of your own doing. If you choose to ban me in an attempt to avoid taking responsibility for your failures, so that you can, at least in your own minds, shift the blame onto me, you may as well delete my account -- you are only lying to yourself, and the action of doing so in that manner is not something I can, or will, forgive -- meaning that not only will that not get you the knowledge you say you want, but that you won't get *anything* further from me. At that point, I'm already gone, and I won't be back.Unfortunately, we're at the point where it's apparent that nobody here is interested in helping me, and I've chosen to shelve this project for now. I will continue to monitor the thread sporadically over the next week or so... it's never actually happened that a post like this from me has brought such a post back from the dead, but hey -- there's a first time for everything, and I try to be optimistic when and where I can.I should mention that, in the past, I've had a goodly bit of help here -- enough so to not only have done so a few times, as it is, but to have thoroughly enjoyed myself at it. It makes me rather sad to see that this has happened this time, and I hope you folks are able to be honest with yourselves (and me) about how this went, because I'd like to continue to stick around.No really hard feelings, yet... you guys take care, OK? :-/* ...especially when the response to my subsequent remark about that is to temp-ban me -- I am nearly always polite; trolling and flamebait posts, unfortunately, tend to bring out my lesser instincts -- but I take special care, when making posts such as this one, and ones calling out a forum community for completely ignoring me for days on end without *ever* having posted in my thread, so it rubs quite hard indeed when I get banned for that sort; there really isn't an excuse or a reason other than "I don't wanna hear it", which is at least as childish IMO as it sounds...

author: Ian.M
author_rank: Super Contributor
timestamp: August 27, 2020, 11:21:08 pm
content: Your remaining questions no longer have anything whatsoever to do with deriving a VGA pixel clock from the signals on an ordinary 15 pin VGA connector, so its not surprising that you aren't getting any responses, especially as answering them would require detailed arcane knowledge of legacy LCD driver cards. which most of us have absolutely no hands on experience with. Sorry I'm one of the many who cant help.Perhaps try a new topic in 'Vintage Computing', linking to this one for background . . .IMHO you should be congratulated for keeping vintage hardware out of skips and trying to find a use for it, even if you aren't a 'only restoration to original condition is acceptable' purist.

author: starhawk
author_rank: Regular Contributor
timestamp: August 28, 2020, 03:58:53 am
content: OK, that's a fair point.I'll contemplate it overnight and decide what to do tomorrow.

author: starhawk
author_rank: Regular Contributor
timestamp: September 01, 2020, 02:41:49 am
content: D'oh! Contemplated... decided... forgot to share the news >_<That was dumb. Sorry.So I discovered I have a different display I can use for what I want to do (the 80s-correct-ish 'deck) but I also realized that I have waaaaay too much on my plate RN in terms of active projects... I tend to have an interest span of max ~3 days thanks to a stupid number of weird mental issues that all manifest in at least mildly unusual ways, and since I get an equally stupid number of project ideas a day, at minimum, I tend to pick the ones that are the most workable (or, occasionally, least *un*workable, lol) of those and I rotate through them as interest waxes and wanes. It's very odd but it keeps me sane -- tends to drive others up the wall -- but, fortunately, it's pretty rare that they have to deal with it on more than an intermittent basis. So I've decided to rotate to other projects for now... if I need help with these again, I'll almost certainly pop up somewhere over here... sometimes tho stuff gets lost in the ether and can't Rand McNally Brain Atlas its way out :-/I'm sure I'll be back at some point, though, inevitably with another project... probably one that's just as crazy... it's just who I am.

author: Ian.M
author_rank: Super Contributor
timestamp: September 01, 2020, 07:08:04 am
content: No worries. If I didn't enjoy 'sanity checking' project ideas I wouldn't be here. Its *NICE* to see one through to real life implementation but I've got enough half-built 'brainwave's on my shelves to know that is not the usual outcome. e.g. there's a wirewrap fairly minimal Z80 board that's been sitting there since I lost funding one term into a microprocessor course about 30 years ago. A couple of times a year I contemplate finishing it off, but the only wirewrap wire I've got in bulk is salmon pink and I doubt I can face the tedium of staring at the offensive pinkness while I wrap the board to match the netlist. At least I can generate a suitable netlist from a schematic nowadays which vastly reduces the tedium. If there's another virus surge this autumn/winter I might even get it built, but I think with an Arduino Nano for I/O instead of the original intention of a UART.

author: james_s
author_rank: Super Contributor
timestamp: November 15, 2020, 07:52:01 pm
content: If nobody answers then it means they either don't know, did not find the topic of the thread interesting so they didn't look inside, or can't be bothered to read a gigantic wall of rambling text. It also tends to put people off when someone starts demanding help and getting mad when nobody helps them. We are not paid consultants or tech support, this is just a community of engineers and hobbyists, you get out what you put in.

author: Ian.M
author_rank: Super Contributor
timestamp: November 15, 2020, 08:28:13 pm
content: 75 days later . . .

author: amyk
author_rank: Super Contributor
timestamp: November 15, 2020, 10:16:41 pm
content: Quote from: Doctorandus_P on August 21, 2020, 03:07:34 amThat's what the "phase" or "image lock" adjustment is for.

author: james_s
author_rank: Super Contributor
timestamp: November 16, 2020, 03:12:20 am
content: Quote from: Ian.M on November 15, 2020, 08:28:13 pmOops, it showed up in my unread threads, I guess I hit my limit of ignored threads again. At least it wasn't years later.