tft display is white quotation

The game will compile and work, I can see it working on the serial monitor.  The issue is the screen stay white.  I can load examples codes and the display screen works perfectly.

So, I have a purpose built pcb with the teensy 4.0 footprint (little did I know the financial implications this would have...I"ve been through >�60 worth of teensy 4.0).

My PCB board size is about 100mm-80mm (all hand soldered with a hot air tool, soldering iron, heat bed not to blow my own trumpet, but I am very good at pcb assembly by hand + I find it therapeutic).

So after half a days soldering, I fire up the board and excellent, the ILI9341 is running at a clock speed of 100mhz (not scoped), lightning fast! Dropped the speed to a more reasonable 20mhz and left overnight for a board test (i always do this, as i have lipos connected etc and like to see if there are any heat issues etc after a 24h run). Found no issues the next morning, graphics test still running so powered off the device.

No changes made, powered up on the third day, and nothing but a white screen on the ILI9341? So i say, must have blew the t4 some how. Hot air removed the t4, on goes the new one and again a few runs later and i get a white screen again? Checked all my pin assignments, voltages and they are all good.

I came to the conclusion that as I was forcing the T4 to be powered of of 3v3 as per (https://forum.pjrc.com/threads/64468...V-power-supply) this was somehow messing with the SPI communication. I canned the T4 and designed and built a T4-SAMD51 clone.

I picked up the project again today and de-soldered my SAMD51 T4 clone pcb as I need speed! The T4 would have been perfect, so tried a few code changes, got the screen running in the setup function (static text etc), but as soon as it enters the loop(), you guessed it....white screen. Its as if the t4 is too fast on spi or something, but I have changed the clock speeds down to 5mhz and yield the same results...

To confirm, I had the T4 intermittently working on both the adafruit ili9341 library and the optimised ili9341_t3. I"ve been through 3 T4s and I have 5 different ILI934 displays. (all give the same results, pull ups, no pullups, removed sd circuitry, ran the T4 at 5v I"ve tried it all!)

I"ve tested the TFT_eSPI-Library with an ESP32 DEV Module (ESP-WROOM-32) and a 2,8" SPI TFT Module with ILI9341 without touch. Everything was fine. For cabling and setup i used the Youtube-video from XTronical "ILI9341 TFT LCD to ESP32 -Full HOW TO ..."

Those results indicate there is no communication happening with the display chip for some reason. Since the TFT_eSPI library is not used for the test this indicates that the library will not be able to talk to the chip either.

This might not work but try it: The displays are fitted with a regulator (U1 on PCB) which is designed to accept 5V input and output 3.3V to the display. These are normally "Low Drop Out" (LDO) which means that if you connect 3.3V to them they still output about 3.0V and this is sufficient for the display chip. Your board may be fitted with a regulator that has a higher voltage loss, so it is worth trying to power the display from 5V connected to the VCC pin. The other option is to bypass the regulator U1 by soldering a link (or adding a big blob of solder) to short across J1 pads. This then links VCC direct to the TFT chip and thus VCC must only be 3.3V (5V with that link will damage the chip).

It may be the display chip has been blown by accidental connections during testing and debugging, but I have found they are quite robust to moderate abuse.

Lastly it could be that your wires are faulty, you can get bad crimps in those link wire connectors and so there is not connection even though it is physically fitted to the pins.

“Collaborative production is simple: no one person can take credit for what gets created, and the project could not come into being without the participation of many”

A white screen usually means at least the back lit LED is working. You need to install the driver to display. Ref 3 shows how to get the white screen and build a kernel.

Available in a variety of sizes, premium MVA (Multi-domain Vertical Alignment) TFT LCDs offer wide viewing angles, fast responses, and excellent color reproductions and depths.

These products have passed our quality standards and inspection process and are now on sale because they have been discontinued. These low-cost solutions are limited in stock so they are ideal for small run projects, prototyping, and testing. Products found here can be modified with value-add services to better fit your application.

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Our advanced, feature-rich TFT displays offer you the very latest solutions to meet the demands of any project. With exceptional resolution, brightness and contrast, optimum readability and performance in all environments, and wide viewing angles, our TFTs also come with optional Projective Capacitive Touch (PCT)read more...

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Range of small to medium sized TFT panels (3.5, 4.3 & 5.7 with and without Touch Panel) suitable for medical equipments, T&M equipment and telecom/ consumer equipments.

Varitronix provide a range of industrial and consumer grade small to medium sized TFT panels. They are suitable for a multitude of applications from navigation systems and test and measurement equipment to digital signage and consumer products. Our displays are available with an analogue or digital interface and are semi orread more...

From TFT color displays to Adafruit display options, choose from the devices available here at Allied Electronics & Automation, part of RS Group. We stock high-quality products by leading manufacturers.

In order to explain what a thin-film-transistor - or TFT - display is, it"s worth explaining what TFT is. This is a field-effect transistor (FET) that is typically used in a liquid crystal display (LCD).

A TFT features a type of metal oxide semiconductor field-effect transistor (MOSFET) that"s made using large, thin films of active semiconductor layers. TFTs also feature a layer that acts as an electrical insulator and metal contacts. This is all layered over a substrate, which is typically glass.

The reason glass is the most commonly used substrate is that TFT is used in LCD displays and there is a TFT for each individual pixel. LCD technology sees liquid crystals manipulate light. The molecules in these crystals move as the temperature changes, and the temperature is changed using an electrical current.

While early LCD screens used a passive matrix of pixels, where each pixel was controlled by an electrical charge, this caused blurring of images on the screen. However, the introduction of TFT technology meant that the mix of pixels became active, thanks to the thin film transistors in the TFT, which are individually controlled.

Pixels in the active matrix used in a TFT LCD display are paired with a transistor that allows individual pixels to maintain charge without an electrical current being required whenever the pixel had to be changed.

As these TFT displays feature a TFT liquid crystal that includes a semiconductor switch for each pixel, each pixel can be directly controlled. This means that the TFT is acting as individual switches for each pixel.

As mentioned previously, early LCD displays were often blurry due to the need for an electrical charge for the pixels. TFT allows the images on the screen to sharpen up, becoming more defined. It also offers a high-quality color contrast and brightness setting.Better for the user

The higher-definition images are ideal for the user in terms of reducing eye strain. TFT technology also means that on a practical level, any fixes that are needed are easier to managed as pixels operate on an individual level.Less energy consumption

In comparison with LED screens, TFT displays have a longer half-life. They are also available in a range of sizes, which means that half-life can be extended again.Versatile

TFT displays are used in everyday applications, from computer work and TV watching, to corporate settings where larger screens are needed for meetings. They are also used in photography, featuring in cameras that require high definition, and navigation systems, mobile phones, and car dashboards.

At Allied Electronics & Automation, part of RS Group, we stock a range of TFT displays that are designed to provide you with the high-quality, high-definition screens you need. From Adafruit displays to interactive TFT LCD touchscreen displays, there are different options available to suit your needs.

We are a leading authorized distributor in North America and stock products by leading names including Lumex, Adafruit Industries, and we also have Focus Display Solutions and IEE displays available.

If you have any questions, our team is on hand to help. Get in touch and we can guide you through the products. You can also find advice in our expert content hub.

Thin-Film Transistor Liquid Crystal Displays use thin-film transistors to control the voltage applied to the liquid crystal layer at a sub-pixel level. The structure of TFT LCDs consists of a TFT “sandwich” and a BLU (Backlight Unit). A typical configuration is shown in the schematic diagram below.

Firstly, between the back and front polarizers, TFT LCD cells are made with two glass substrates – one for color filters, the other for a TFT array – and a liquid crystal layer sandwiched in between.

Secondly, BLU (Backlight Unit) usually consists of three components: BEF (Brightness Enhancement Film), DBEF (Dual Brightness Enhancement Film), and LGP (Light Guide Plate).

For normally black TFT LCDs, if we follow along a piece of light setting off from its backlight source, it will bea)guided uniformly by LGP;b)reflected and enhanced by BEF and DBEF;c)polarized by the back polarizer;d)polarization changed by twisted LC under the voltage applied by TFT arrays;e)“tinted” red/green/blue by corresponding color filter of the subpixel;f)let through the front polarizer by matched polarization; andg)finally, it will reach the surface and appears in viewer’s eyes.

For normally white panels, processd)will be the opposite – known as the polarization rotation effect, light is twisted in a voltage-off stage and can pass through the front polarizer by default, thus displaying white normally. However, when the voltage applied increases, this polarization rotation effect would be gradually diminished. And the light would not be able to pass through the front polarizer anymore without changing its polarization. In this way, certain pixels will appear in different colors.

Normally black LCDs have higher contrast and wider viewing angles without grayscale inversion phenomenon compared to their normally white relatives. And whether TFT LCDs are normally black or white depends on their LC switching mode:

2Chen, HW., Lee, JH., Lin, BY.et al.Liquid crystal display and organic light-emitting diode display: present status and future perspectives.Light Sci Appl7,17168 (2018).https://doi.org/10.1038/lsa.2017.168

As previously mentioned, TN mode functions with the polarization rotation effect. Under traditional TN/VA display mode, the liquid crystal molecules are vertically arranged, with a relatively narrow visual angle. When an external force is exerted on the screen, the liquid crystal molecular structure will sink in a herringbone pattern to slowly recover – a pattern called vertical alignment. Therefore, an evident “water ripple” usually appears when the display surface is touched and impacts the user experience. In comparison, the VA mode provides higher contrast. And MVA (multi-domain vertical alignment) is an upgraded version of VA with improved viewing angles.

Under IPS mode, the LC directors are horizontally (homogeneously) aligned, which makes them free from ripple effects when made into touch panels. The drawback is lower transmittance, especially for LCs in a “dead zone”close to electrodes.

Are you looking for a 3.5" TFT Display to add to your product or project? We"ve got a handful of different TFTs with a 3 1/2 diagonal dimension. Most of them support 16-bit Parallel, 18-bit Parallel, 8-bit Parallel, 9-bit Parallel, RGB, and SPI. While all TFTs are transmissive, we carry some that are bright enought to be sunlight-readable. As you can see we offer a variety of pixel densities for this size, 480x640, 320x480 and 320x240. If you"re looking for a different 3.5 inch TFT display that isn"t listed here, please contact our support team, they"d love to help you find the perfect display for your requirements.

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