Ben Heck's FPGA LCD Driver Hack

Ben finds an LCD that is the perfect size for a pinball display, but it only runs composite video and that just won’t do. Ben uses his oscilloscope to figure out how the LCD works so he can reverse engineer it using an FPGA.
Learn more about the Tektronix spectrum analyzer at
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[@intheblues]

Ben - Your vast knowledge on everything electronics is off the planet. Every video I shake my head and smile about how much you know, retain, and explain. :-)

[@markconger8049]

I can't believe I have just found this video after two years of searching how to possibly use displays without controllers. This is the best tech video I've watched all year (2017.) Thank you, Ben!

[@petereric95]

I didn't understand a single thing from this entire video except that you bought a car lcd from ebay :D

[@funkyant]

haha

[@AndyHope970]

haha yeah, I understood because I've done electrical engineering, but I was a bit surprised he went to this level of detail for TBHS.

[@martinsalko1]

why are you watching then? i mean like what get you to watch the show?

[@homeuser5]

lol

[@martinsalko1]

marcoswi Please explain why?

[@psiewert83]

Ah you know...just messing around with my $14,200 oscilloscope.

[@Damaniel3]

I actually worked on the development of this particular scope and I can't afford one... :(

[@scottdotjazzman]

Yeah, that's always bothered me about this show. Element14 seems to have little concept of a budget where a multi-thousand dollar scope is a no-go unless you use it for a living. (That said, inexpensive 4-channel Tek storage scopes can sometimes be had on fleabay for $300-500 or so. I was lucky and scored a 2430 from a ham radio neighbor for free.) @Damaniel3, Tek should pay their engineers better for that price!

[@nogrend]

looking for this comment

[@insanitystudios8219]

I picked up an old analog 100mhz dual trace osilloscope from the classified ads. only cost me $25 and I definitely got my money's worth out of it

[@voxertv5057]

@@scottdotjazzman 10 gHz 1nm ADC for you

[@sergioorjuela7896]

I really enjoyed the exposure to more advanced electronics. This is definitely one of my favorite shows. Thanks Ben!!!

[@malgailany]

One of the most interesting videos I've seen recently! Reverse engineering graphic LCD has always been a hard task without datasheets. Also showing how an FPGA can be used as a high-speed driver while most microcontrollers may fail to achieve the task. I hope to see more details, and how to display useful information on the LCD. Thank you for interesting video.

[@brandonlewis2599]

This was the best episode yet. I really enjoyed this. l especially like how this episode showed in detail the process of reverse-engineering, and all (or most, anyways) of the guess-work that is involved. And how you just need to jump in there and experiment. In some sense, it's a shame that Ben got it working on the first try. Would have learned more watching him struggle a bit. But hey, I guess it looks good for your sponsor. Finally, you finally gave me an appreciation for what an FPGA can do that a micro-controller or dedicated logic can't. It would take a pretty serious (and expensive) micro-controller to drive that LCD -- if indeed it could be done at all. But it would also take a ton of work to build a circuit up from logic gates to it. The FPGA reduces this to a 25-minute episode. Thanks, Ben!

[@shana_dmr]

I love how you explained "FP" in FPGA as 'can be programmed anywhere, even on a field' :D

[@arcadeuk]

Ben, This is possibly one of the best videos you have done to date, and as I am a pinball collector, it is very relevant :)

[@jonathanbirdwell7852]

I loved this episode, especially the differential video explanation and the use of the fpga on your channel.

[@odrabil123]

I'm still amazed how you found the clock frequency and were able to identify each bit. I don't know if you did that quickly or if it took you some time but edited the video. In any case, what an amazing exercise! In my opinion, this kind of videos is truly motivating for future electronics/electrical engineers :D

[@tekvax01]

just a point of clarification... front and back porch are for the horizontal sync, the pre equalization and post equalization pulses are used in vertical sync.

[@TheSugarwolf31]

This video has perfect timing. I am working on converting an old laptop lcd into an hdmi monitor and it really helps to see the process step by step.

[@RoyHess666]

Dear Ben, this video was very very technical and very explanatory. I really liked how you explained the stuff, good work! Can't wait to see what you will do in the future with this :) Greetings from germany!

[@StoneFlange]

I second that--I'm still very new to programming, but I was able to follow a good deal of this and it gave me a better appreciation for the old LCD question ;) thanks for the in-depth explanation! I know some people don't like this much technical info but I loved it!

[@muskateer12345]

nazi

[@muskateer12345]

***** is what ur mum called u when u wr born

[@aronheck7584]

Very nicely done, especially with that FPGA. That is another level of complexity

[@VacFink]

This one was a nice change. Over my head if I'm honest but something I've been curious about for a long time. Glad to see more pinhacks. I want to add a lot of video elements to my own pinball project (Fifth Element) and this is an exciting solution. Great motivation to get deeper into programming and clear explanation of why this kind of reverse engineering/hack is as uncommon and difficult. Thanks for taking on the challenge and sharing!

[@dudenamedclem]

Dang Ben you are definitely geeking out on this episode! LOVE IT! Thanks :)

[@MarkusBlechschmidt]

I'm always astonished by the capabilities and mechanics of electronics. Nice job :-)

[@DoctorWhy777]

Also found this on wiki in regards to color depth. 18-bit Almost all of the least expensive LCD displays (such as typical twisted nematic types) provide 18-bit color (64 × 64 × 64 = 262,144 combinations) to achieve faster color transition times, and use either dithering or frame rate control to approximate 24-bit-per-pixel true color,[12] or throw away 6 bits of color information entirely. More expensive LCD displays (typically IPS) can display 24-bit or greater color depth. You said that it uses diferential pairs because of the speed, so when the wiki article says "64 × 64 × 64 = 262,144 combinations) to achieve faster color transition times" that kinda makes sense to me. Question why is it using 7bits instead of 8bits? Right enough beer and youtube commenting for me, Love this video!!!!

[@maxxsinner]

I have never understood FPGA's. This was an awesome intro into what can be done with them and a really interesting look at how video signals work.

[@jamescatania]

Although most of us don't have the equipment/knowledge to do this ourselves, thanks for taking the time and effort to explain how it works and how to do this with fpga, now at least I know how to do a fast cycle between bits with differential signalling, without the need to change current states from high to low... awesome video very well done and thank you again

[@badermeinhof123]

Alyson rocks. You should bring her on the show more often. Awsome hack. Did understand that you did something and wish i had the knowledge and tools to do the same.

[@rluquett]

You are amazing! love all your videos and every time I come to your channel I learn something new that I can use in my professional field. Thanks!

[@philipacovington]

FPGAs are great for retro-computing and learning how a CPU works. I am implementing Ben Eater's 8-bit computer in an FPGA in a series of videos on my channel for anyone interested.

[@Backbeardjack99]

Awesome!!!! Just awesome! Please Ben, do a complete FPGA tutorial!

[@KelvinSmoke]

Wow, this shot way over my head. Go Ben. Look, I spent two months designing and printing handlebar-end mirror holders for my motorcycle....Go me...

[@MichielHaisma]

Very cool project. Would love to see more FPGA's. I would definitely back this on Patreon!

[@DanielChristiansen]

This was friggin' awsome! Thank you!

[@Madmax23419]

Nice episode, and great results. :) How fast was the clock? Was a logic analyzer not a better choice for this job?

[@coolnamesTV]

Very cool video Ben!

[@ajfrances1]

EE here, the technical nature of this video makes me happy!

[@PDRIFT86]

Really like how you explain everything, great video and awesome hacking.. The outtakes at the end are pretty funny too, keep it up and have a nice day.

[@diasslo]

You are on a whole new level, my respects

[@lbochtler]

This is exactly what i need for a project im working on. Thanks Ben! (though it is a bit big)

[@theslvrbullt]

Man, FPGAs were so much fun to play with in College. Watching you reverse engineering that screen was pretty awesome as well. Makes me wanna start looking through my spare parts box and see what I could mess with. ... Also reminds me I need an FPGA dev board. Anyone have any good suggestions on one?

[@theslvrbullt]

Toni T800 Tax returns are around the corner. Might be a good investment for the summer. Will try. Thanks. :)

[@jaapweel1]

I always thought that at least part of the point of differential pairs was that they are less susceptible to noise because if both wires pick up the same noise, it cancels out when you look at the difference.

[@Jefferson-ly5qe]

Jaap Weel Noise isn't usually a big problem in digital systems since they are so robust against interference. Great for reducing interference in analogue stuff like mike cables though.

[@TheTurnipKing]

@@Jefferson-ly5qe It seems like something that's going to be a bigger factor the lower the voltage becomes (for faster rise/fall times). In an older 5v device the distinction between a logic 0 and a logic 1 is pretty clear, and small voltage fluctuations probably won't change the signal. If you're dealing with very low voltage signals the difference becomes increasingly small, and even small fluctuations will start to matter.

[@andrewkowalczyk1156]

Actually a legitimately useful application: I've got so many LCD's lying around with obnoxiously large driver boards and composite input, implementing it on an FPGA is a much nicer fix than hacking in the original board to a project.

[@chaemelion]

I always thought resistance to interference is the reason for differential signaling, rather than the speed granted by low voltage levels as Ben explained. The idea is any kind of EM interference or other power fluctuations would raise or lower the differential pair signals equally thereby leaving the relative voltage between the two unchanged, even as their absolute voltages may fluctuate. Someone correct me if I'm wrong.

[@jasonbeuke495]

Well done, I personally would like to see you build more stuff :D

[@adrianruth9054]

The Ben Heck Show Please do more FPGA content!!

[@tHaH4x0r]

Finally a build that requires some actual skill. You could use DRAM with 2 partitions for 2 frames. 1 frame is constantly written to the screen at the update rate (30 or 60hz) whilst the other is free to access and modify by a microcontroller (cortex M4 or something) which prevents tearing and enables slow microcontrollers to write to the screen with a decent update rate. When the frame has been updated, the FPGA switches the ram access to update the screen with the new frame.

[@Neceros]

Wow, thank you. You've done in a few minutes what my electronics class failed to do. Electricity is so hard to understand for me.

[@dstorm19]

Love it! Need more on this one!

[@FoolsGould]

I love TBHS, it's like watching and learning from the professor I never had :)

[@spieagentl]

This looks like a fun project! I'm currently taking Digital Logic at the school I attend, and I hope to apply my experience with FPGA's for activities like this.

[@thestud2]

You do it the way you want to do it. Keep Creating!

[@Jeremydge]

Seriously, I don't have the 0.01 of your knowledge in electronic, but damn I love your show (Sorry for my english, i'm french) but you have a great show!! Keep it going!!Seriously!

[@jonmayer]

I was really hoping this was a part 1 of 2. Obviously, you need a way to input a different signal for frame pixel data and have the FPGA translate it out.

[@buggsyspam]

Wooo, this one really went over my head. Interesting all the same.

[@michaelsalomone8031]

Ben, new subscriber, most of what you do goes right over my head, but I love watching and hopefully something valuable will sink in. How much was the lcd? Are you going to give COLOR DMD a run for their money ?

[@n1cobenz]

Hey Ben, why are you guys using an external led for the cyclone rather than oune of those built in? Btw, love the show, much love to you guys

[@simpsonizer]

Thanks! I learned a lot from this. For example I knew something about dif-signaling but I now have a clearer pic of how to read logic states just from your video! I knew what a FPGA was, but the programming and chip and pin management I did not know about! The only thing is when the gate arrays are programmed, does the program have to re-connect all the gates each time the FPGA chip is turned on? Or is static once programmed (like flash memory). Very interesting and makes me wish I had a multi-channel o-scope and a dev board. Only issue is getting a understanding of the programming lol.

[@KuraIthys]

I've never done much practical work, but i've read a lot. From what I've come across, most FPGA's are paired with an external flash memory. (a ROM if the FPGA is a component in a static design, or some kind of solid state storage. Eg flash rom or the like, if it's changeable). At boot, the FPGA loads it's state from this memory, and then configures itself to match. Depending on how many gates the FPGA has, this can be many megabytes. Some FPGA's have the required non-volatile memory on the chip itself, but many do not. Either way, the state is re-loaded every time the FPGA powers on. Even in a completely static design, if it has an external chip providing configuration (even if it were a non-programmable ROM), you could in theory remove that chip, put in one with a different program, and completely alter what the FPGA does... They are basically volatile devices. Turn off the power, and an FPGA loses it's 'program'

[@0xbenedikt]

I did something similar, not that difficult using a oscilloscope. I interfaced a graphical calculator lcd, by sniffing the lines and finding out the data format.

[@sarowie]

Such a high end scope, differential signals and then using the ground leads with alligator clips or how HF-Engineer call it: Antennas. I mean: If it does the job it is good enough, but the signal integrity would be better with shorter ground loops.

[@kirbyman1kanden7pf]

Nicely done!!!!

[@akay48]

can we get a link of that video of a kitten cuddling with a sloth?

[@kentvandervelden]

When attaching the ground of the scope probes, is it necessary to attach all of them? Since the grounds are most likely linked inside of the scope, is attaching only a single ground sufficient? I'm referring to the setup at 7:00. Great video, thank you!

[@tomwilkinson4630]

A really great video. I've criticized your content, but that was a great video. I like this new direction a lot!

[@BourneToLiveRich]

I'm just curious Ben, how long did you spend figuring out where everything you needed to know about the LCD screen to do this and if decoding the signals was a big issue?

[@bufo333]

So this is great and all but how do you feed the fpga an actual video signal?

[@berkayozturk3991]

Great video , thanks.

[@ivarsandin7275]

I think that you should try to use this display for a pinball machine. The DMD's are so expensive these days so it would be nice to have a cheap way to replace one and also having the possibility to make it another color. Cheers!

[@rorschak8175]

you are amazing :) i like watching your videos we learn much from you :)

[@LanternLabs]

You could use the composite input, it'll stretch your video funny, just pre-squash the video so when its stretched it looks right. Thats how 16x9 SD content is produced from the same signal as 4x3...

[@PatFarrellKTM]

Since you found the proper part for the LCD and driver, does Element 14 now carry it so we can buy just what we need?

[@TunsaMcHaggis]

which is fine, if you have a screen with a known resolution.

[@jemert96]

It doesn't work like that, he wrote the LCD driver himself using an FPGA. The FPGA you can buy, but you still have to program it

[@migwelder18]

Ben Heck is so smart. What can't he do?

[@bikutoso]

I have a quick question, where should i buy parts for electronics projects i have?

[@timrichter1980]

Having not much experience with oscilloscopes, I wonder why the signals are so distorted @7:22 ? Does it come from the high frequency, and thus the reason why they chose differential pairing? I'm sorry for stupid questions :)

[@Stabby666]

Hi Ben, do you have the verilog that you used for this? I'm using a similar display and it'd be great to use the code to get started!

[@travbrack]

So would it be possible to convert an HDMI signal using the same FPGA or would other hardware be needed?

[@Noahg929]

Ben, On the revisited raspberry pi mame project next episode could you talk more in depth about batteries and how to power a portable. I'm building one myself and don't know what to do.

[@CPLBSS88]

Is there a 'crude' way to do this without a scope that is quicker than trial/error by plugging the wires into a breadboard and testing?

[@markconger8049]

GraymanTactics - I am by no means qualified to definitively answer this question, but I can guess, right? LOL Ben needed the specifics of the signaling to create the FPGA code but all he had was documentation from a similar unit. This was in an onscreen footnote during his presentation with the dry erase board. So, without knowing for sure but having a good starting point using the comparable documentation he used the scope to figure out the rest, and a good thing too because he discovered one piece of the signal was "active low" instead of "active high" like the documentation said. Without that knowledge he'd have had a much harder time getting the FPGA code to work. What I would like to see is the other half of this project's equation - getting output from a video card into the display so it can be used with a single board computer.

[@ApiRote]

Can considerer a i2C signals of the SDA an SCL as a differential signals too? They build words too... Or is a simetrical voltage in a bias? I am an amateur forgive me :) Thanks for your videos!!

[@josescxavier]

There is any post with more info on this? Per example the fpga source code? Thank you

[@jet_flyer]

please do more with FPGAs I'm curious about them

[@machielymker6301]

a little question: what is the best os for the raspberry pi to use on a media/console/'pc' machine/project?

[@shmickist]

"Raspbian" is most commonly used. add "XBMC" packages for media playback.

[@feeterican]

That looks like a 21:9 ratio and that would be great for personal movies on a plane or passenger in a car.

[@TunsaMcHaggis]

is that lvds? could you use a generic vga to lvds driver board for it?

[@fabts4]

Most impressive hack I've seen. The one I least understood as well.

[@phuocbolip]

i want to buy this lcd . what number , model for lcd ? mr ben give i know ,please

[@blackIce504]

Hi ben, many people have been saying just buy some LVDS boards of ebay and for the most part there cheap, but my issue with those are that you never know if your going to get full speed of the LCD, so i like your idea of using an FPGA as it has the more then enough power to handle any LCD and any res at any speed possible, you could also make a program to test LCD with it so. So i really do like your idea and shall try it sometime as i have a grave yard of LCD that most likely have blown boards. are you able to share a link of your program that you made for the FPGA?

[@jamesgarlick4573]

How can you make a multiple hdmi input tv? I am wanting to make a rear projection tv with my own diy made projector so I want to be able to have multiple inputs.

[@gudenau]

I want to do this with a different display, I am sure this will help.

[@denizengt]

I think I need an electronics refresher. A lot of this went over my head. Great process though

[@StingrayOfficial]

Impressive flexing of skills/knowledge in this video. *FLEXXXXX*

[@eiohulhuhunyu]

What is the minimum Oscilloscope analog bandwidth and sample rate to do this?

[@MSI2k]

Awesome fucking episode, man!

[@sykotheclown1]

You could turn that into one badass homebrew VR headset.

[@PinBallReviewerRepairs]

What about the Color DMDs that have come out for DMD style pinball machines? Could you not code up your own pinball machine and do your own code? There is even an option to have it look like the original DMD with the dots or you can have the option of no dots. But what is a DMD with out the dots right? ;)

[@Sonicdude10]

OK. So a FPGA is good for figuring out how the signal bus drives the display. Now the real question is if it can be implemented on a cheaper board. A CPLD is out of the question due to the clock rate needed to get all the signals in. If I remember a 112 MHz clock was used for 800x234 resolution. By my calculation (probably wrong as I used simple math) I figure that a 190 MHz clock signal is needed to get all the data needed in for 1024x310 resolution. A simple microcontroller is out of the question for this. Something that can run at upwards of 200 MHz would be needed to drive the 8 wires for the system. Perhaps a small ARM board could be used. Something like this could possibly work: electronicdesign.com/microcontrollers/200-mhz-system-chip-arm-core-targets-lcd-apps It is a 200 MHz ARM based LCD driver chip that is capable of driving a 800x600 LCD. That's 480,000 pixels per frame. At 1024x310 resolution there are 317,440 pixels that need to be driven per frame. If the device can be reprogrammed to drive this odd ball resolution the controller can work assuming it can do 4 pairs of LVDS and accept something like digital RGB input. The controller also promises to be fairly cheap. A LOT cheaper than the FPGA used here. Probably wrong here but thought I'd give it a try. Any ideas on my thoughts? Wrong, right, maybe? I don't know this level of data signalling too well so correct me if wrong.

[@Uterr]

we just need to check datasheet for particular lcd panel

[@Sonicdude10]

***** Confused? I never mentioned anything about the oscilloscope. I know what it does. I was using the data figured from the readings on the scope. The signals "sniffed" by the scope are what the original composite based driver board for the LCD put out. I was using those numbers. As for the universal LVDS board, maybe. It would need to be programmed for the LCD due to the resolution and number of data lines. Those universal boards aren't fully universal. They might or might not need to be reprogrammed. I suspect with this screen they probably would need to be.

[@mrlazda]

You can use CPLD, but you will not save lot of money (if you will save any, you can find cheap Cyclone V boards), but again it depends of functions you want to do. LH7A400 is not best solution for this application (according to datasheet it is meant to direct drive LCD with parallel bus) same as ATSAMA5D34A ...

[@kraftlab]

GaryBlack Keep in mind this is a prototype. Using the FPGA was just a quick way to create a working prototype to test out the theory. If this goes forward something more robust and cost reduced would be developed.

[@kraftlab]

***** I've seen you talk about the converter board a lot in the comments so I thought I would let you know that Ben is well aware of those boards. I thought the greater purpose was clear from the video but in the final application the goal is to use the LCD as a pinball DMD display. There is already a micro in the existing system that dives the current LED based DMD display. It already outputs signals for that type of display. If he used a converter board then he would have to output some kind of video signal, VGA, HDMI, DVI, whatever. With this system he is basically generating a special custom signaling between the micro controller and the FPGA which then would drive the LCD. Which means no need to generate any kind of video out from the microcontroller. I wrote the software that we use to generate the output frames on the DMD and have already started on a revised version for this format so I have some idea of how the whole thing would go together.

[@michaelperugini4199]

is there a part 2?

[@NLmkkillah]

You are a magician!

[@jcx5750]

I like this guy...

[@phataldude]

Ben should totally do kickstarters for his projects!!!!!!!!!!!!!!!!!!!

[@DigitalEyesStudios]

How can you use thar display for a custom dashboard? Thanks in advance.

[@Supramonk]

Hello I would like to use that LCD to build Synthesizer , Is this Touch screen like the Ipad ? I am looking to build a synth with a touch screen is this possible ?

[@Masculineish]

Love this guy :D

[@electroGoal]

It that possible to make driver for smartphone display using this FPGA. If possible then how

[@bzhmaddog]

Anyone know the model number of this LCD panel ? I am trying to find it only but I can find only a 10" version

[@erikhedb]

Do I need a 1Ghz scope to do this? Is 50 or 100 MHz sufficient?