Need help with LCD controllers

[Yuriman]

I'm working on a project where I'm trying to find or assemble a small (~4") LCD, preferably an IPS panel, with a composite video input. I'm looking to display output from a small camera which has only composite out. There are plenty of small off-the-shelf screens available on eBay which will accomplish what I'm looking to d - I have a few in a bin, and frankly they're all lousy. Mostly this will be a learning exercise.

I started my search for a 4" IPS panel (which I'm aware tells very little about the quality of the image) and found there are several interfaces that seem to be commonly used - I've seen 26 pin LVDS, 30 pin LCDS, 40 pin TTL, 50 pin TTL, a proprietary(?) serial connection for Raspberry Pi, DSI/MiPi, 3SPI... and then there's the signaling on top of that. I'm trying to wrap my brain around all of these different connectors/interfaces and understand them.

Here's one example of an assembled "kit" on ebay:

https://www.ebay.com/itm/HDMI-VGA-2...rentrq:f827c5881620abc322da6284fffa2c65|iid:1

It appears to be 50pin TTL from the screen to a board that converts it to 40pin TTL, and that runs to a controller board.

This screen is advertised as being for a Raspberry Pi:

https://www.ebay.com/p/OPENBOX-Wave...m=262637018015&_trksid=p2047675.c100005.m1851

^ Conveniently it has HDMI, and I could get a composite to HDMI converter, but I wouldn't learn much from that. I'm unsure what the 26 pin black connector is.

This screen has a "3SPI" interface:

https://www.ebay.com/itm/4-inch-480...rentrq:f827c5881620abc322da6284fffa2c65|iid:1

MiPi:

https://www.ebay.com/itm/5-5-inch-7...OLED-screen-with-MIPI-interface-/112837469923

~

These controller boards are cheap and abundant on eBay, and look like a promising place to start, rather than at the screen itself:

https://www.ebay.com/p/HDMI-VGA-2av...m=182460581252&_trksid=p2047675.c100005.m1851

This screen looks like it uses TTL, but as I'm not very familiar with the various connectors it's hard to say:

https://www.ebay.com/itm/4-inch-TFT...hash=item1c948dc7d8:m:m9f73tgEGg99q02WkUxL94g


I don't mind ordering something inexpensive and finding out it doesn't work as I'd hoped, so long as I learn something from it, but I thought I'd ask here first. There are a bunch of acronyms which mean almost nothing to me, and I'm as much looking at connectors as anything else.

 

[sdifox]

err, this is entirely up to you no? you have to decide how to drive the panel.

 

[Yuriman]

err, this is entirely up to you no? you have to decide how to drive the panel.

That's the point - this is something I know almost nothing about. I'm likely to buy a controller and panel that will not work with each other, because I lack sufficient knowledge to understand what works with what, and why. I suppose what I'm asking is if someone can go over the various interfaces/connectors, and perhaps make some specific part recommendations other than the cheap undocumented junk I've found browsing eBay, with explanations as to why.

 

[sdifox]

That's the point - this is something I know almost nothing about. I'm likely to buy a controller and panel that will not work with each other, because I lack sufficient knowledge to understand what works with what, and why. I suppose what I'm asking is if someone can go over the various interfaces/connectors, and perhaps make some specific part recommendations other than the cheap undocumented junk I've found browsing eBay.

but what are you going to use to control the controller? usually you go with TTL driver coupled with a TTL driven LCD panel. what is the source you are going to use? It really depends on how low level you want to go.

 

[Yuriman]

Thank you, I wasn't aware of TTL drivers. This screen would need a driver then?

https://www.ebay.com/itm/4-inch-TFT...hash=item1c948dc7d8:m:m9f73tgEGg99q02WkUxL94g

Can you show me an example of one, and explain how it works with the panel and controller?

My source is composite, from a camera. My apologies if I'm not asking intelligent-enough questions, but I'm trying my best based on my current knowledge. I don't yet know what to ask.

 

[sdifox]

Thank you, I wasn't aware of TTL drivers. This screen would need a driver then?

https://www.ebay.com/itm/4-inch-TFT...hash=item1c948dc7d8:m:m9f73tgEGg99q02WkUxL94g

Can you show me an example of one, and explain how it works with the panel and controller?

My source is composite, from a camera. My apologies if I'm not asking intelligent-enough questions, but I'm trying my best based on my current knowledge. I don't yet know what to ask.

That is usually coupled to a microcontroller. Example is smart thermometer. Like I said, first define your project, then figure out parts.

Are you just trying to build a composite source display?

 

[Yuriman]

Are you just trying to build a composite source display?

Basically yes, in part because I was unable to find something premade that met my wants. I'm mostly concerned with learning about displays and controllers in general though, so I can apply the knowledge more broadly and figure this out unaided in the future.

So, what are some ways I could get that 4" IPS panel to display from a composite source? What parts would I need?

 

[sdifox]

Basically yes, in part because I was unable to find something premade that met my wants. I'm mostly concerned with learning about displays and controllers in general though, so I can apply the knowledge more broadly and figure this out unaided in the future.

So, what are some ways I could get that 4" IPS panel to display from a composite source? What parts would I need?

There is nothing to learn, you are literally hooking up the ribbon cable to the driver/input board, add power and source and you are done. Unless you want to build/program the actual input board yourself.

 

[Yuriman]

There is nothing to learn, you are literally hooking up the ribbon cable to the driver/input board, add power and source and you are done. Unless you want to build/program the actual input board yourself.

Very helpful, I must already have known the answers to my questions. You already saved me from buying a panel and controller and probably not knowing why it wasn't working after plugging everything in.

Looking at TTL, since it seems most common. Take this kit for example:

https://www.ebay.com/itm/VGA-AV-LCD...121078?hash=item2aa3e1f576:g:k2oAAOSwBPJasOZu

I notice there is only a single board. Does that mean the driver and controller are on the same board? And, what do I need to know about the compatibility between controllers and boards? Does the controller need to be specific to the resolution of the screen being connected to it, or can they be "smart" enough to negotiate this to some degree?

Is the same true of LVDS? Does it also need a separate driver, which goes in-line (?) to the screen?

What is the black interface on the back of this screen?

https://www.ebay.com/p/OPENBOX-Waveshare-4inch-HDMI-LCD-RESISTIVE-Touch-Screen-800x480-High-Resolution/1886670455?iid=262637018015&_trkparms=aid=555018&algo=PL.SIM&ao=2&asc=50999&meid=208a4004c6a544c68e20f530d1a16c55&pid=100005&rk=1&rkt=12&sd=112956605434&itm=262637018015&_trksid=p2047675.c100005.m1851

Is that LVDS, or is it proprietary to Raspberry Pi? I'm guessing since it has an HDMI port on the screen, it must have a controller and driver on the circuit board.

 

[sdifox]

Very helpful, I must already have known the answers to my questions. You already saved me from buying a panel and controller and probably not knowing why it wasn't working after plugging everything in.

Looking at TTL, since it seems most common. Take this kit for example:

https://www.ebay.com/itm/VGA-AV-LCD...121078?hash=item2aa3e1f576:g:k2oAAOSwBPJasOZu

I notice there is only a single board. Does that mean the driver and controller are on the same board? And, what do I need to know about the compatibility between controllers and boards? Does the controller need to be specific to the resolution of the screen being connected to it, or can they be "smart" enough to negotiate this to some degree?

Is the same true of LVDS? Does it also need a separate driver, which goes in-line (?) to the screen?

What is the black interface on the back of this screen?

https://www.ebay.com/p/OPENBOX-Waveshare-4inch-HDMI-LCD-RESISTIVE-Touch-Screen-800x480-High-Resolution/1886670455?iid=262637018015&_trkparms=aid=555018&algo=PL.SIM&ao=2&asc=50999&meid=208a4004c6a544c68e20f530d1a16c55&pid=100005&rk=1&rkt=12&sd=112956605434&itm=262637018015&_trksid=p2047675.c100005.m1851

Is that LVDS, or is it proprietary to Raspberry Pi? I'm guessing since it has an HDMI port on the screen, it must have a controller and driver on the circuit board.

First one is complete kit, you just need to supply signal and power. You need to know what kind of TTL signal your panel needs. Universal 50 pin TTL cable.
example
https://www.ebay.com/itm/LCD-Contro...r-Drive-LVDS-TTL-Display-Screen-/152850085515

not vouching for vendor or anything, just an example, notice in the description it lists protocols supported.



You don't need touchscreen do you? the second item is designed to be coupled to an RPI board. Picture number four shows you the way it is supposed to be coupled to the rpi. It is an all in one driver/input board/touchscreen item.

 

[Yuriman]

No need for touchscreen, it seems many of the inexpensive panels on eBay have it, but I would just leave it disconnected.

So, how is LVDS different?

 

[sdifox]

No need for touchscreen, it seems many of the inexpensive panels on eBay have it, but I would just leave it disconnected.

So, how is LVDS different?

different signalling scheme. Much lower power requirement and is the preferred interface now for flat panels.

http://www.differencebetween.net/te...n-technology/difference-between-lvds-and-ttl/

 

[Yuriman]

I assume it's similar in that they also need a driver? How universal are the drivers and controllers?

 

[sdifox]

I assume it's similar in that they also need a driver? How universal are the drivers and controllers?

Yes, but there are converters.