Display types: Difference between revisions

Revision as of 13:54, 8 March 2024

Backlit flat-panel displays

CCFL or LED backlight

https://nl.wikipedia.org/wiki/CCFL

Self-lit

OLED

QLED

On image persistence / burn-in

VFD

larger segments
dot matrix VFD

Vacuum Fluorescent Displays are vacuum tubes applied in a specific way - see Lightbulb_notes#VFDs for more details.

Lighting

Nixie tubes

Mechanical

Mechanical counter

https://en.wikipedia.org/wiki/Mechanical_counter

Split-flap

https://en.wikipedia.org/wiki/Split-flap_display

LED segments

7-segment and others

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

7-segment, 9-segment display, 14-segment, and 16-segment display. If meant for numbers will be a dot next to each (also common in general), if meant for time there will be a colon in one position.

These are really just separate lights that happen to be arranged in a useful shape.

Very typically LEDs (with a common cathode or anode), though similar ideas are sometimes implemented in other display types - notably the electromechanical one, also sometimes VFD.

Even the simplest, 7-segment LED involves a bunch of connectors so are

often driven multiplexed, so only one of them is on at a time.
often done via a controller that handles that multiplexing for you

Seven segments are the minimal and classical case, good enough to display numbers and so e.g. times, but not really for characters.

More-than-7-segment displays are preferred for that.

https://en.wikipedia.org/wiki/Seven-segment_display

DIY

LCD character dislays

Character displays are basically those with predefined (and occasionally rewritable) fonts.

Classical interface

The more barebones interface is often a 16 pin line with a pinout like

Ground

Vcc

Contrast

usually there's a (trim)pot from Vcc, or a resistor if it's fixed

RS: Register Select (character or instruction)

in instruction mode, it receives commands like 'clear display', 'move cursor',

in character mode,

RW: Read/Write

tied to ground is write, which is usually the only thing you do

ENable / clk (for writing)

8 data lines, but you can do most things over 4 of them

backlight Vcc
Backlight gnd

The minimal, write-only setup is:

tie RW to ground
connect RS, EN, D7, D6, D5, and D4 to digital outs

I2C and other

Matrix displays

Small LCD/TFTs / OLEDs

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Small as in order of an inch or two.

Note that, like with monitors, marketers really don't mind if you confuse backlit LCD with OLED, and some of the ebays and aliexpresses sellers of the world will happily 'accidentally' call any small screen OLED if it means they sell more.

This is further made more confusing by the fact that there are

few-color OLEDs (2 to 8 colors or so, great for high contrast but only high cotnrast),
[[high color][] OLEDs (65K),

...so you sometimes need to dig into the tech specs to see the difference between high color LCD and high color OLED.

When all pixels are off they give zero light pollution (unlike most LCDs) which might be nice in the dark. These seem to appear in smaller sizes than small LCDs, so are great as compact indicators.

Video or not?

These often don't connect video cables, but have their own controller, and their own video RAM.

It matters that the lowish amount of pixels can be updated via an interface that is much less involved than a monitor - until you try to display video you might get reasonable results over SPI / I2C.

There is a semi-standard parallel interface that might make video-speed things feasible. This interface is faster than the SPI/I2C option, though not always that much, depending on hardware details.

Say, something like the TinyTV runs a 216x135 65Kcolor display from a from a RP2040.

Also note that such hardware won't be doing decoding and rescaling arbitrary video files. They will use specifically pre-converted video.

If it does speak e.g. MIPI it's basically just a monitor -- but that amount of pixels also likely means you want something more RAM-heavy for a framebuffer, and more computationally heavy if you want to do something that looks remotely fancy at a speed you might call video.

Interfaces

ST7735

LCD, 132x162@16bits RGB

ST7789

LCD, 240x320@16bits RGB

https://www.waveshare.com/w/upload/a/ae/ST7789_Datasheet.pdf

SSD1331

OLED, 16bits RGB https://cdn-shop.adafruit.com/datasheets/SSD1331_1.2.pdf

SSD1351

OLED, 65K color

https://newhavendisplay.com/content/app_notes/SSD1351.pdf

HX8352C

https://www.ramtex.dk/display-controller-driver/rgb/hx8352.htm

ILI9163

LCD, 162x132@16-bit RGB

http://www.hpinfotech.ro/ILI9163.pdf

ILI9341

https://cdn-shop.adafruit.com/datasheets/ILI9341.pdf

ILI9486

LCD, 480x320@16-bit RGB

https://www.hpinfotech.ro/ILI9486.pdf

ILI9488

LCD

https://www.hpinfotech.ro/ILI9488.pdf

PCF8833

LCD, 132×132 16-bit RGB

https://www.olimex.com/Products/Modules/LCD/MOD-LCD6610/resources/PCF8833.pdf

SEPS225

LCD

https://vfdclock.jimdofree.com/app/download/7279155568/SEPS225.pdf

(near-)monochrome

SSD1306

OLED, 128x64@4 colorsTemplate:Vierfy

https://cdn-shop.adafruit.com/datasheets/SSD1306.pdf

SH1107

OLED,

https://datasheetspdf.com/pdf-file/1481276/SINOWEALTH/SH1107/1

Round

GC9A01

backlit LCD, 65K colors, SPI

https://www.buydisplay.com/download/ic/GC9A01A.pdf

@@ Line 297: / Line 297: @@
 {{stub}}
-Small as in order of an inch.
+Small as in order of an inch or two.
@@ Line 305: / Line 304: @@
 call any small screen OLED if it means they sell more.
-This is further made more confusing by the fact that there are few-color OLEDs (2 to 8 colors or so), and [[high color][] OLEDs (65K),
+This is further made more confusing by the fact that there are
-so you sometimes need to dig into the tech specs to see the difference between high color LCD and high color OLED.
+* few-color OLEDs (2 to 8 colors or so, great for high contrast but ''only'' high cotnrast),
+* [[high color][] OLEDs (65K),
+...so you sometimes need to dig into the tech specs to see the difference between high color LCD and high color OLED.
 <!--
@@ Line 314: / Line 315: @@
 -->
-One ones with more colors are often '''backlit LCD style''' {{comment|(and them sometimes incorrectly referred to OLED. When buying off ebay and aliexpress, maybe double check the specs)}}
-There are also '''OLED style''' displays.
-Many cheap OLEDs are single-color, and no shades, so while they are high contrast, they are ''only'' high contrast.
 When all pixels are off they give zero light pollution (unlike most LCDs) which might be nice in the dark.
@@ Line 328: / Line 322: @@
 '''Video or not?'''
-These often don't connect video cables, but have their own controller.
+These often don't connect video cables, but have their own controller, and their own video RAM.
+It matters that the lowish amount of pixels can be updated via an interface that is much less involved than a monitor - until you try to display video you might get reasonable results over SPI / I2C.
-Displaying video on them is doable on some, but more finicky to do.
+There is a semi-standard parallel interface that might make video-speed things feasible.
+This interface is faster than the SPI/I2C option, though not always ''that'' much, depending on hardware details.
-The SPI interface should work anywhere, but is more limited in what it can do and how fast it can do it.
+Say, something like the {{imagesearch|tinycircuits tinytv|TinyTV}} runs a 216x135 65Kcolor display from a from a [[RP2040]].
-A parallel interface may be faster, though not always ''that'' much, depending on details.
+Also note that such hardware won't be doing decoding and rescaling arbitrary video files.
+They will use specifically pre-converted video.
-That said, something like the {{imagesearch|tinycircuits tinytv|TinyTV}} runs a 216x135 65Kcolor display from a from a [[RP2040]], with specifically converted video.
+If it ''does'' speak e.g. MIPI it's basically just a monitor -- but that amount of pixels also likely means you want something more RAM-heavy for a framebuffer, and more computationally heavy if you want to do something that looks remotely fancy at a speed you might call video.
-Note that features are a precarous balance, in the sense that if it ''does'' speak MIPI it's basically just a monitor,
-but that implies a bunch more bandwidth, something with the according controller (though having a controller-side framebuffer is easily a few hundred kilobytes). <!--
-If it speaks something similar, you might need to bit bang it, and
-doing that at the speeds required for something you might call ''video'' will be a challenge from a lot of hardware.
--->
 ====Interfaces====
 <!--
-* 3-line SPI
+* 4-line SPI
-* 4-wire SPI
+* 3-line SPI ([[half duplex]], basically)
 * I2C
 * 6800-series parallel
 * 8080-series parallel interface
-The last two are 8-bit parallel interfaces, the main difference being the read/write and enable
+The last two are 8-bit parallel interfaces,
+the main differences being the read/write and enable, and in timing.
+(they are references to Intel and Motorola origins of their specs{{verify}})
 If they support both, 8080 seems preferable, in part because some only support that?
 Speed-wise, ''in theory'' parallel can be multiples faster,
 though notice that in some practice you are instead limited by the display's controller, and the difference may not even be twice (and bit-banging that parallel may take a lot more CPU than dedicated SPI).
+There are others that aren't quite ''generic'' high speed moniutor interfaces yet,
+but too fast for slower hardware (e.g. CSI, MDDI)