I remember buying my first Raspberry Pi. I loved how cheap it was and had a million dreams about what it could do. However, one issue I ran up against pretty early on was that I had to hook it up to a monitor, keyboard, and mouse every time I wanted to use it. To get around this, I purchased a touchscreen. There are a lot of options out there so I figured I’d make a short guide to help anyone looking to purchase a Raspberry Pi touchscreen.
What do you need to consider when buying a Raspberry Pi touchscreen? When purchasing a touchscreen for a Raspberry Pi you will want to consider the size of the screen, how the screen is connected to the board, and if it’s drivers are compatible with Raspberry Pi devices.
Screen size is the most obvious consideration what looking at a Raspberry Pi touchscreen. Should you go with a screen as large as possible, something super small and portable, or somewhere in the middle?
Larger touch screens definitely have their advantages. They make it a lot easier to see what’s going on as well as giving access to a larger keyboard. If you find yourself fat-fingering on small touchscreens than you might be happier going with something in the 10-15 inch range. A larger screen will also give you more of a tablet feel if that is what you are going for.
The downside of larger screens is the increased power consumption. Some larger screens will not be able to be powered through the Raspberry Pi but will need to have a secondary power source. This may mean extra cables laying around or a shorter battery life if you are hoping for a mobile setup.
With an average sized screen of around 7 inches you tend to get the best of both worlds. You’re not paying for a large screen, your keyboard is a decent size, and your power consumption isn’t off the charts. If you don’t have any issues with a screen this size, it is the one I would recommend.
Small touch screens are also an option for Raspberry Pi projects. You can get screens as small as 3.5 inches. With a screen this small, the cost and power consumption is considerably less than the medium and large touchscreens. The downside is you lose a lot of precision on a screen this small. You will most likely want to use a stylist with a small screen as you are now smaller than most consumer phone screens at this point.
There are 4 different ways in which a touchscreen can be connected to a Raspberry Pi. Each has it’s advantages and disadvantages.
Using the HDMI port is by far one of the easiest ways to connect a touchscreen to your Raspberry Pi. This connection type is the most common among screens so you can go with a variety of makes and models. By using an HDMI port you also have the advantage of leaving all of the GPIO ports open. The downside this connection method is that the touchscreen will need to have it’s own power source as HDMI is unable to send enough power to keep a screen on.
Display Serial Interface
The Display Serial Interface or DSI port comes standard on most Raspberry Pi models. The only models with out are the Raspberry Pi Zero and Raspberry Pi Zero W. This port carries many of the advantages of the HDMI. While the connection is not as standard for touch screens, there are still many available that have this connection. It is very common in small handheld devices such as GPS’s and smaller tablets. This connection type does not provide power so you will need an external power input or have to use the GPIO header to power it through your Raspberry Pi.
Lastly, you can always you the versatile GPIO header to connect a touchscreen. There are multiple Raspberry Pi Hats that can mount directly onto the GPIO with plug and play functionality. If you are making a small tablet or are not planning on using the GPIO this may be a great option for you as this method also takes care of power though the 5V header. If you are considering using this connection type, be sure that you don’t have any other big plans for the GPIO as screens often take up a majority of the pins.
Drivers And Compatibility
You should always be checking for compatibility when looking for Raspberry Pi parts. Most general manufacturers have the larger Windows and Mac markets on their minds and may not have developed drivers for Linux based systems. Be sure the read the documentation before making a purchase. Also be aware of the power and processing requirements for the screen. Most Raspberry Pi models are not able to output resolution above HD (Raspberry Pi 4B is able to do 4k) and touchscreens may require a significant amount of external power. Make sure that you are planning according to your budget and finished product designs.
Other Display Options
If you are not set on having a touchscreen, there are a number of other display options that are available for Raspberry Pi. The most obvious alternative is to have an LCD display that does not have the touch functionality. These are usually significantly cheaper that their touchscreen counterparts and contain almost all of the same functionality.
Stepping farther away from the LCD screens, there are TFT displays. These are very similar to the displays that would be connected through the DSI port but will require a breadboard to be wired to the GPIO. These are significantly cheaper than the DSI screens and also can be touch sensitive.
Next on the list are EInk displays. These are the displays that you think of on an e-reader. It does not have the appearance of being back lit but also is only capable of showing a couple of colors. EInk displays have the advantage of continuing to display even after their power is turned off. The big disadvantage is the very slow refresh cycle. Most EInk displays have a refresh cycle of over 1 second.
Lastly, there is also the option of an LED matrix. This type of display is simply a grid of LED lights that can display simple patterns. These look similar the the old Lite-Brite toys from the 90’s. They can come in a variety of sizes but most have between 8 and 64 diodes in either direction. These can work great for displaying simple text. Depending on the size of the display, these can go from being very minimal in power consumption to needing their own dedicated power source.
How much power does a touchscreen need?
The touchscreens that are powered directly from a Raspberry Pi tend to have roughly a 500mA power requirement. They will draw about 2.5W, which is substantial when considering using a battery to power your project. Larger screens can take as much as 10W of power but require their own power supply as a Raspberry Pi cannot supply that much power to a single device.