config.txt display_default_lcd adafruit 2.8 tft lcd display brands

Going further I plugged a HDMI display and Voila! there is my Desktop, but no mirror at all. Even the touchscreen is working and I can move de cursor over the Desktop (HDMI) with my finger on the 2.8" display.

Going further again, with the HDMI plugged and choosing console I can startx and the desktop goes to HDMI, then I can see running Xorg using top from SSH. Restart again the script and I choose mirror, no HDMI connected and black screen over the TFT, but I also can see Xorg running.

This application note is part 1 of our 2 part TFT LCD screen series. Part 1 discusses configuring the screen resolution of a TFT with a Raspberry Pi. Part 2 discusses calibrating the touch screen of a TFT. Click here to read part 2.

This application note discusses how to setup a TFT touch screen display with Raspberry Pi. The display chosen for this project is a 7-inch LCD with a capacitive touch feature. The display has 1024x600 pixels of resolution and when calibrated for the Raspberry Pi can display 16.7M colors. With a few changes to the Raspberry Pi configuration files the dimensions of this display can be matched for perfect resolution.

The display in this project is easy to interface with the Raspberry Pi because it has an LVDS to HDMI backpack adapter connected. This makes it simple to connect an HDMI cable between the two devices and begin your project. In a few steps any display can be configured for optimal resolution. Additionally, this display has a capacitive touch screen which can be calibrated through Raspberry Pi for accuracy. These features combined with the large size of the display make it a great choice for a variety of Raspberry Pi projects.

Connecting the TFT to the Raspberry Pi is simple and only requires a few steps. The display has a HDMI connection backpack interfaced with the device so there is no need for soldering or individual pin connections. If you have used Raspberry Pi before, you will notice that the connection to the TFT is standard and straightforward. Before powering the Raspberry Pi you should make all the necessary connections to the screen. Plug in the HDMI. Connect the CTP port with a micro-USB cable. Power the screen with micro-USB cable connected to a USB port on the Raspberry Pi or a power adapter that provides 5V. You only need three connections to the HDMI backpack module on the TFT.

You will need a mouse and keyboard to setup the Raspberry Pi before the touch screen is enabled. You will also need a micro SD card with Noobs loaded onto it before powering. (Installing NOOBS) Lastly you will need an ethernet cable to setup internet to download or update the software. Once you power the Raspberry Pi, Noobs will give you some options of what software platform you want to install. For this project I chose Raspbian (recommended option). (Installing Raspbian) After installation you will likely notice that the graphics are distorted or that the width and height of the screen are not the desired dimensions. This is because Raspberry Pi’s auto-calibrate feature doesn’t recognize this display. So, to get the best picture, we will need to calibrate it manually.

If it’s not terrible, and you can still see what you’re doing on the display, you can do this through Terminal. We want to edit the “config.txt” which loads from the boot file. The other option is to remove the SD card and load the file on the computer or setup SSH and edit the file remotely.

The file will open in a text editor called nano. We need to add the specifics of our display to the file by adding the following commands to the file:

The last three fields of hdmi_cvt can be omitted, and they will refer to the default values. The other commands declare the use of HDMI and create a new mode for the hdmi_cvt specifications. For detailed information on these commands and others that function in the config.txt file refer to the Raspberry Pi documentation website.

If the screen is still not perfectly configured for the device, a few other tweaks can be made to the config.txt file. Adjust the overscan parameters to add or remove pixels on the edges. For example, adding 33 pixels to the “overscan_right” parameter corrects overflow of the image on the right side of the screen. This takes a few trial and error attempts to perfect.

If you notice that turning safe mode off results in a blank screen you could have a bad HDMI connection. First try another HDMI cable. If this does not fix the problem, then we can increase the signal strength of the HDMI by editing the config_hdmi_boost command in the config.txt file. The standard setting in the configuration file is set as:

This default value is 2 and can be increased up to 11 if necessary. Try adding this command at increased increments until the issue is solved. You will need to edit the config.txt file on your computer or remotely for this step.

With only a few changes to the Raspberry Pi’s default configuration file the TFT can become compatible with the Raspberry Pi. This display is a great choice for interfacing with the Raspberry Pi because it has an HDMI connection type which makes for any easy setup. After the resolution and is set to a desired value we can now optimize the touch feature of the display. See here for more information on how to further calibrate this display.

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4) After the image has finished writing, open the config.txt file in the root directory of the TF card, add the following code at the end of config.txt, then save and quit the TF card safely.

5) Insert the TF card into the Raspberry Pi, power on the Raspberry Pi, and wait for more than 10 seconds to display normally. But the touch is abnormal at that time, and the touch needs to be calibrated as the following steps.

You can perform touch calibration by clicking the Raspberry Pi icon on the taskbar, selecting Preferences -> Calibrate Touchscreen, and following the displayed prompts.

4. After calibration, the following data will be displayed. If you want to save these touch values, you can replace the data in the red circle with the data in the corresponding position in 99-calibration.conf.