wifi lcd display free sample

With all the advantages and disadvantages, lcdds are essentially a good choice for those who see the TV starting from 4k smartphone. Nowadays, in addition to the wholesale models, lcdds are essentially a good option for those that don ’ t have the capacity of a device.

This tutorial shows how to use the I2C LCD (Liquid Crystal Display) with the ESP32 using Arduino IDE. We’ll show you how to wire the display, install the library and try sample code to write text on the LCD: static text, and scroll long messages. You can also use this guide with the ESP8266.

Additionally, it comes with a built-in potentiometer you can use to adjust the contrast between the background and the characters on the LCD. On a “regular” LCD you need to add a potentiometer to the circuit to adjust the contrast.

Before displaying text on the LCD, you need to find the LCD I2C address. With the LCD properly wired to the ESP32, upload the following I2C Scanner sketch.

After uploading the code, open the Serial Monitor at a baud rate of 115200. Press the ESP32 EN button. The I2C address should be displayed in the Serial Monitor.

Displaying static text on the LCD is very simple. All you have to do is select where you want the characters to be displayed on the screen, and then send the message to the display.

The next two lines set the number of columns and rows of your LCD display. If you’re using a display with another size, you should modify those variables.

Then, you need to set the display address, the number of columns and number of rows. You should use the display address you’ve found in the previous step.

To display a message on the screen, first you need to set the cursor to where you want your message to be written. The following line sets the cursor to the first column, first row.

Scrolling text on the LCD is specially useful when you want to display messages longer than 16 characters. The library comes with built-in functions that allows you to scroll text. However, many people experience problems with those functions because:

The messageToScroll variable is displayed in the second row (1 corresponds to the second row), with a delay time of 250 ms (the GIF image is speed up 1.5x).

In a 16×2 LCD there are 32 blocks where you can display characters. Each block is made out of 5×8 tiny pixels. You can display custom characters by defining the state of each tiny pixel. For that, you can create a byte variable to hold  the state of each pixel.

In summary, in this tutorial we’ve shown you how to use an I2C LCD display with the ESP32/ESP8266 with Arduino IDE: how to display static text, scrolling text and custom characters. This tutorial also works with the Arduino board, you just need to change the pin assignment to use the Arduino I2C pins.

We present the design of a 320x256 RGB LED electronic display board intended to be used as a platform to present information of current and future events in schools or office buildings. The proposed design can display up to eight different images, which may include text and graphics. The rendering of these images is done periodically, with the duration of the period being controlled by the user. The images can be created from slides of a power point presentation or directly from stored photos. Loading of new images to the display board is done wirelessly via WiFi from an Android App running on a portable device such as a tablet or a smartphone. We present experimental results on a completed and fully operational prototype system, which includes the RGB LED display board together with the custom-built microcontroller board as well as the Android App. While the current use-application is as an informative message board in a school set-up, the proposed system can be used in any other indoor application. For outdoor usage, the system would require an additional weather-proof enclosure and fixtures.Metadata Overview

There are generally three main categories of electronic displays. In the first category, simpler and more traditional, one can find the systems that use character LCD displays with two or more rows and 10, 20 or other number of characters per row, such as the 16x2 character LCD [1]. This type of display can typically display static or moving text messages [2]. The second category includes all systems that use graphic LCD displays. Examples in this category include small embedded LCD and touch-screen TFT displays (e.g., 320x240 pixels), digital photo displays, and systems that use LCD monitors as the primary method to display text and images [3]. Finally, in the third category, we can find RGB LED displays. Examples in this category include mostly outdoor scoreboard displays as well as highway and business side billboards. Their complexity and costs are high and depend on the size, which is typically large; see for example the commercial products from Daktronics [4]. However, one can find smaller size examples created by hobbyists, including designs that use just one 64x64 RGB LED matrix panels [5] or just one 32x32 matrix panel [6]. The advantages of RGB LED displays compared to the color LCD displays include better visibility in sunlight conditions, better contrast for crisper details, purer colors, and reduced reflection. However, their power consumption is typically large and their cost relatively high. Finally, while most of these example designs are controlled by microcontrollers, there are solutions that use field programmable gate arrays (FPGAs) as well for improved speeds [7].

The problem of designing and prototyping large RGB LED displays has been less researched in the past literature. That is because this is more a problem of development rather than of theoretical research and because there exists already many commercial offerings of such displays from established companies, some of which were mentioned in the previous paragraph. Nevertheless, one can find prior research studies on power supplies for RGB LED displays or especially on new circuit solutions for LED drivers. For example, the study in [10] proposed a microcontroller-based driver whose objective was to maximize the LED efficiency. They reported a prototype for a 3x3 LED matrix and achieved efficiency greater than 92%. A dimmable multi-channel RGB LED driver was reported and studied with a nine LED string in [11]. Energy savings was the objective of the LED driver studied in [12]. The driver uses a multilevel pulse width modulation (MPWM) driving method combined with simple video signal conversion techniques. It was demonstrated for a 32x32 LED pixels display. The study in [13] addresses the challenges of active image adjustments and processing, considering the non-linearity of the LED display element. They propose a method for the nonlinear adjustment of the images contrast. The advantage of the proposed method is that the images can be displayed on OLED or LED displays with the unified luminance signal, for grayscale images, or with separate RGB controls. Other studies focused on the design of individual LEDs; such an example is the study in [14] that proposed solutions based on dielectric compound parabolic concentrators (CPCs) in order to increase brightness. Such studies are outside the scope of our paper, which focuses on the system integration design aspects, both hardware and software, and prototyping of large RGB LED displays.

In this paper, we present the completely open-source design of a 320x256 RGB LED electronic display board intended to be used a platform to present information of current and future events in schools or office buildings. While the current use-application is as an informative message board in a school set-up, the proposed system can be used in any other indoor or outdoor application (for outdoor usage, the system will need weather-proof casing though). Designed to be cost-effective yet extendable, we hope this design will be adopted and improved in other practical and educational settings.

The integrated 2MB of flash memory of the MCU is used as the primary frame buffer that stores the currently displayed image on the display. It is shown as the “Frame Buffer 2” in Fig. 2. An additional external 2MB parallel SRAM chip is used to store the image to be displayed next. This memory, indicated as “Frame Buffer 1” in Fig. 2, effectively plays the role of a cache between the MCU and the memory system formed by eight different Flash memory chips indicated as “Flash 1..8” in Fig. 2. The eight 2MB flash chips store the current presentation slides or “project”, with one slide per flash chip. The flash chips—physically placed close to the microcontroller to reduce communication delays—were chosen due to their low cost, ease of use, and large number of write cycles (100,000 cycles typically). High performance is achieved by the MCU’s 50MHz External Bus Interface (EBI) feature that is exploited to fetch image data into the primary frame buffer, “Frame Buffer 2”. The WiFi module is the popular and low cost ESP8266 module, which provides its own connection to the device that runs the Android App and thus it does not require a separate Internet service. A new “project” represents eight different images, which are uploaded via the WiFi connection from the App to the eight flash chips.

In addition to driving the display, the microcontroller also has several other tasks to service. During normal operation, up to eight images are stored across eight 256KB serial flash memory chips. This external non-volatile memory acts as long-term image storage, and stores image data across MCU resets and power cycles. It is accessed through a Serial Peripheral Interface (SPI). The MCU can read and write entire images worth of data to a flash chip in about three seconds. When a project is programmed into the system, each image is stored in the SPI flash, while the number of images for the project and the cycle time between images is stored into the microcontroller’s internal flash.

The microcontroller also has an external parallel 256KB SRAM. It is able to read and write data to this SRAM through the External Bus Interface (EBI). EBI allows external memory to be attached to the MCU and it treats it just like any other virtual memory address space. This allows data in EBI SRAM to be treated like a normal byte array in C firmware. During normal operation, while an image is being shown on the screen, the next image to be displayed is moved from SPI Flash into EBI SRAM. When the image is ready to be displayed, it is moved all at once from EBI SRAM into the internal frame buffer and shown on the screen. In this memory structure, EBI SRAM acts as a data cache, since moving data from EBI SRAM into internal RAM is much faster than moving data from SPI Flash into internal RAM. Using this technique, image transitions appear seamless.

The MCU has a serial interface with a WiFi module included on the logic board. This is the main interface between the Android app (described in the next section) and the system. Through the WiFi interface, the user can turn the screen on and off, adjust the brightness of the screen, and load new projects into the system. The WiFi module and the MCU communicate through a UART interface. A ring buffer in MCU firmware allows massive amounts of data to be transferred at a time from the WiFi module into the MCU.

A custom Android App, named MU-MatriX (available already for download on Google Play) was developed to allow the user to create and upload to the display system new “projects”. A “project” consists of eight images that form a presentation displayed periodically at a configured interval. The app stores each project’s name, set of images, and duration between image switch into its internal application storage. After naming a new project, a user can populate the project with images, selecting them one-by-one from their device. The images can maintain the aspect ratio of the original image or stretch to fit the size of the display board. There is also the option to rotate images in 90 degree intervals before adding them into the project. In the background, any selected image is saved off into a 320x256 bitmap with black background filling in any gaps created by the aspect ratio lock. As images are being added to a project, they can be reordered by simple up and down arrows next to their thumbnail on the “Edit Project” screen. A spinner widget provides a drop-down selection for the project-level property of duration between slides.

The default display board device is automatically stored under the user’s device list on app installation. The IP address and port number used by default for the ESP8266 WiFi module (on the logic board) are simply placed under a device name “Default Display Board”. The app allows more than just this one display board configuration to be saved in memory, allowing for this system to scale to multiple screens all managed under one app. A device control screen gives the app simple commands to send the Wifi module on the Logic Board: Power On, Power Off, and a screen brightness slider that sends a numeric value between 5 and 100. Simple WiFi messages holding single-line commands are sent over the network using the TCP protocol. Uploading a project to the Logic Board from the application takes a little bit more work and is given its own screen within the app. After selecting one of the projects, one of the hardware devices, and pressing “Upload”, a progress bar and message will become visible on the screen tracking the conversion and transmission of each image within that project. After all the images have been sent, a message will notify the user of the upload completion.

The conversion step of the project upload performs a variety of operations to turn the 320x256 bitmap into a 245,760 byte long array. This contains the hexadecimal values which represent the intensity of color for each LED in the pixel’s RGB matrix. The transmission operation starts by telling the Logic board to stop multiplexing images across its screen (to allow it to focus on receiving the new data) and clear the parallel RAM chip (about to be filled with the image data). The app separates the long byte array of data into smaller chunks that it sends across a TCP connection to the ESP8266 WiFi module on a new thread. This thread sends a chunk of the image data to the ESP module, and after receiving confirmation from the microcontroller that the message arrived safely, it updates the progress bar on the main thread via a Handler. After one full image is sent, commands are sent to specify which non-volatile flash chip to store the image into. After the full project is sent, a message containing the number of images the project contains and the time duration between images is sent over WiFi again to be stored into non-volatile program flash and used during the state machine operations.

The electronic display system consumes significant power due to the large number of LEDs. The power supply can provide up to 50 A. Thus, users must be cautious of the high currents supplied to the RGB LED panels. In our current prototype, connections are accessible on the back of the panel, so, there is the risk of immediate contact with such connections. We plan to enclose the entire panel inside a wood enclosure with a back lid such that no electrical contacts can be directly accessed (such an enclosure is not part of the current design and is not described in this paper or in the documentation).

The following table lists the metrics or figures of merit that were tested and validated using the complete hardware prototype of the electronic display system as well as the fully operational Android App.

The objective of this experiment was to verify that eight images can be saved to the flash chips located on the logic board and that all images can be displayed correctly in order and repeatedly. The testing strategy was to cycle through all eight flash chips, write and then read the image data from, and drive the LED panels to display each of the images. First, all eight flash chips were written to with eight different images. Then, each image was read from the flash chips and displayed onto the panels. The images displayed on the panels were verified whether they were the desired image. This was repeated five times and all images were changed each repetition to verify the reliability of the entire process of writing and reading images into the flash chips. During this process, we monitored the error (as percentage of pixel data written or read incorrectly) during both writing to and reading from the flash chips. This test was successful with an outcome of 0% error.

The objective for this experiment was to identify the optimal number of bits for the color representation used to render images. The constraints of this experiments included the amount of memory available inside the microcontroller to implement the buffer (stores the data of the image currently being displayed) as well as the time it takes to upload all eight images from the App to the board’s flash chips. The desired color representation was 12-bit color code, which would be capable of generating 4096 different colors per pixel. However, due to how the 5x4 panels (64x64 pixels each) are driven by the only 8 PWM frames (giving 3 bits per color channel) with information about pixels forming an image, we arrived at the compromise of using only a 9-bit color code, which is still capable of generating 512 different colors per pixel. This color code ensures that images have reasonable color resolution to make them appear in natural colors onto the display. While 12-bit color code would obviously be preferable, the 9-bit color code is sufficient to be able to display rich colors, yet to restrict the amount of memory required, achieve better performance (as refresh rate), and to naturally match the PWM control of the 64x64 LED panels.

The objective of this experiment was to verify the Android App and the logic board can communicate successfully via WiFi. The ESP8266 module, mounted on the logic board, was used for this connection. The test plan for this experiment involved sending 20 images of data from the Android App to the logic board and verifying that no data was lost during the transfer. Testing to be sure that no data was lost in the transfer involved displaying the image onto the screen and verifying that the image appeared as intended. This test was successful with an outcome of 0% error.

The objective of this experiment was to verify that the microcontroller was fast enough to properly display the images without any flicker. This was performed by using an oscilloscope to measure the frequency of the clock and latch signals and seeing that the images displayed on the panels did not flicker. This procedure was repeated five times on five different images to verify that a range of different detailed images can be shown without flickering. This test was successful with an achieved refresh rate of 30Hz.

The electronic display is completely reproducible as all the hardware components are readily available from various vendors and the complete design files are made publicly available. Designed to be cost-effective yet extendable, we hope this design will be adopted and improved upon in other practical and educational settings. At the minimum, the display can be replicated as presented and used out of the box. We envision two main ways to extend it. First, the display size could be increased by adding more 64x64 RGB LED panels to the rows and columns. This will potentially require power supplies capable of providing higher currents. Also, the firmware residing on the MCU of the controller board will need to be changed to account for display sizes different than the current 320x256 LEDs. Second, the system could be extended to add the capability of playing video. Such an extension will be more challenging. It could be done by keeping the display continuously connected to the App (or the Internet), which would stream desired videos. Another idea is to modify the controller board in order to include larger capacity flash memory or a micro SD card, which could store large video files. While doable, such changes are major changes to the current design.

We believe that our design has more unique value in educational contexts, because in business contexts, companies can purchase such display boards from established digital display power-houses such as Daktronics. In educational contexts, one can use the proposed design as an open-source flexible “workbench” for various studies in courses on embedded systems, digital signal processing and design, or wireless communications. For instance, in a typical embedded systems course, examples of such studies may include: 1) Investigation of the power consumption and of firmware techniques to reduce it, 2) Laboratory experiments where students are required to implement essential modules of the firmware. Examples of such modules can cover: the WiFi communication between the design and the mobile app, the module responsible for debugging features via the UART peripheral of the microcontroller, etc. The existing design could serve as a platform to verify software development tasks covering microcontroller firmware and mobile app development as well.

The bill of materials for the electronic display system is listed in Table 2. Detailed specifics on each of the electronic components (i.e., resistors, capacitors, etc.) are not included here for brevity (the list is too long); however, they are available in the online repository.

Complete design files, both hardware and software, and documentation are made publicly available in the online repository. In the simplest scenario, one can simply duplicate the proposed electronic display system. The most challenging aspect in this process would be the soldering of all the SMD components on the logic board, because it requires prior experience and SMD soldering skills as well as the availability of a reflow oven. Otherwise, everything is rather simple and straightforward to assemble and to program. Extensive efforts were put into implementing a comprehensive help and debugging capability for the logic board. To use this capability, one would only need to connect a serial terminal (such as Putty) to the USB port of the logic board, then, follow the prompts. More detailed information on this debug ability is provided in the documentation for the firmware.

Perhaps the most notable aspect regarding the technical implementation of this design is that it provided an excellent educational value for the duration of two semesters. More specifically, 1) it required us to develop our own method of “packetizing” the pixel data of all eight images transmitted from the mobile app to the display board via WiFi and 2) it provided a context where hardware and firmware designers needed to team-up with mobile app software developers and create a product that works reliably and  repeatedly. This required good communication skills and collaboration to develop common testing strategies.

The entire design is made open source and publicly available. The following repository contains both hardware and software design files. Additional information, including a project poster and a short video presentation is available at (project “RGB LED Electronic Display”): http://dejazzer.com/hardware.html (archived version)

We presented a completely open source design of a 320x256 RGB LED electronic display board created from a 5x4 array of 64x64 pixels RGB off-the-shelf panels. The electronic display is intended to be used as a display board of information of current and future events in schools or office buildings. The information is presented under the form of eight images or slides that are displayed periodically by the board. The images can be uploaded to the board system via WiFi from an Android App that was custom developed for this purpose. A complete prototype was built and tested successfully. Despite its relatively high overall cost, the proposed electronic display system is extremely easy to use. The complete design files, both hardware and software, are made publicly available. As such, we hope that this design can serve as a starting point for other researchers and educators who are interested in developing more complex RGB LED electronic displays.

As discussed in the Section “Reuse potential and adaptability” above, the proposed electronic display could be extended in several ways. Currently, we are planning to extend the design in order to be able to play video as well.

X. Lv, K.H. Loo, Y.M. Lai, and C.K. Tse, "Energy-saving driver design for full-color large-area LED display panel systems," IEEE Trans. on Industrial Electronics, vol. 61, no. 9, 2014.

M. Andrei, S. Moldovanu, and N. Nistor, "Nonlinear transformations applied to image processing on the RGB LED display," Int. Symposium for Design and Technology in Electronic Packaging​ (SIITME), 2018.

C. Peng, X. Li, P. Zhang, L. Xiong, and X. Liu, "RGB high brightness LED modules for projection display application," Journal of Display Technology, vol. 7, no. 8, 2011.

Based on ESP32 series chip, Kaihong Zhigu launched Niobe U4 development board kit, integrated 2.4GHz WiFi and Bluetooth dual-mode, supporting ultra-high RF, low-power, low-voltage and low-cost contactless reader applications; in addition, it also supports lithium battery power supply and charge/discharge management; recently it has also been integrated into the OpenHarmony community backbone, supporting OpenHarmony 3.1 operating system, providing a complete SDK and a large number of application routines to facilitate rapid secondary development.

To help you better understand the OpenHarmony Niobe U4 development board, this issue summarizes the Niobe U4 trial experience, environment building, LVGL porting, ADC button, LCD display, weather forecast, multi-threaded application demos, leading you to master the NiobeU4 development board usage, application skills.

Description: Thank you for the holiday gift sent by Kaihong Zhigu and electronic enthusiasts, the following NiobeU4 development board to do an unboxing experience. The NiobeU4 development board received this time, is already assembled, the main components are the base board and 1.44 inch SPI color LCD, detailed unboxing instructions are as follows.

Description: This development board with a 135×130 TFT screen, the controller used is ST7735, SPI interface, 16-bit. The first two articles have been tested for the display of the screen, with the conditions to port the GUI, this article we port LVGL.

Description：This project implements spaceman to change position. In order to be able to achieve their own network clock display, you need to integrate WiFi and lcd display routines, this article for 107 and 202 demo integration, their own synthesis of 108 for compiled display. Network to obtain weather information has not been written, and subsequently want to set up an infrared detection using the speaker for weather announcements.

Description: NiobeU4 is an IoT device development kit based on ESP32U4WDH, integrated 2.4GHz Wifi and Bluetooth dual-mode. This article mainly completes ubuntu-20.04.5 system environment build, repo tools, cross-compile, get the project source code, build test source code iotlink process.

Description: This subsection mainly uses 202demo to add WiFi to get cJSON weather data, the process is a bit convoluted, but the data got, not yet on the LCD for display.

Description：Kaihong Zhigu development board NiobeU4 on board a spi interface display, the resolution of 130 * 135, used to display some key information is also very good. This article uses this screen combined with multi-threaded to display Chinese and English, graphics, etc.

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This is a new Pi Pico display from Waveshare with many more pixels. It is a 2inch LCD display module, designed for Raspberry Pi Pico, with an embedded ST7789VW driver, 65K RGB colours, 320x240 pixels and an SPI interface. A Pi Pico can be plugged into the rear of the screen for very easy connection without any soldering. It sports 4 simple button switches for user input. It is bright, colourful and easy to program. The makers supply an example program (see below), which includes the display driver, making it very easy to get started. The manufacturer"s wiki can be found at: