Universal TFT Display Backpack 2
2nd May 2026
This is an updated version of my Universal TFT Display Backpack, a microcontroller board based on an ATtiny814 that can accommodate a range of different Adafruit and AliExpress colour TFT displays:
The Universal TFT Display Backpack displaying the BarChart example on
an AliExpress 3.5" 480x320 TFT display.
It's ideal as the basis for applications based on my TFT graphic libraries.
Features
Like the earlier board Universal TFT Display Backpack it has the following features:
- It supports a range of different Adafruit and AliExpress Colour TFT displays with resolutions from 128x128 up to 480x320; for details see the tables below.
- The display connection header pin holes are staggered so you can push-fit the display without soldering. This is especially useful if you want to try different displays in an application.
- It includes an I2C interface, allowing you to connect sensors and other peripherals. For example, you could use this to make a graphical weather station.
- There is space on the board to fit a 32.768kHz crystal for use as the timer clock source with 1-series or 2-series processors, for use in clock projects.
This updated version has the following additional features:
- It includes space for an optional MCP9808 I2C temperature sensor, for projects involving temperature measurement.
- The board includes additional pin holes to accommodate AliExpress displays with an additional SDA-0 pin, and Adafruit displays with an additional TE pin.
- The board has been enlarged slightly to make room for clearer labelling of the pins.
Microcontroller
The board is compatible with the following microcontrollers in an SOIC14 package:
| 0-series | 1-series * | 2-series * | ||||||
| Device | Flash | RAM | Device | Flash | RAM | Device | Flash | RAM |
| ATtiny3224 | 32KB | 3KB | ||||||
| ATtiny1604 | 16KB | 1KB | ATtiny1614 | 16KB | 2KB | ATtiny1624 | 16KB | 2KB |
| ATtiny804 | 8KB | 512B | ATtiny814 | 8KB | 512B | ATtiny824 | 8KB | 1KB |
| ATtiny404 | 4KB | 256B | ATtiny414 | 4KB | 256B | ATtiny424 | 4KB | 512B |
| ATtiny204 | 2KB | 128B | ATtiny214 | 2KB | 128B | |||
* To use the 32.768kHz crystal on the TFT Backpack you need a 1-series or 2-series device; this option is not supported by the 0-series.
For the prototype I used an ATtiny814, shown bold in the table, as this has enough flash memory to run all the examples provided with the Compact TFT and Tiny TFT Graphics Libraries.
Note that the board is not compatible with the AVR-series 14-pin devices such as the AVR16DD14; these have a different pin layout.
Adafruit displays
The Universal TFT Display Backpack is compatible with the following Adafruit displays:
| Supplier | Size | Width | Height | Voltage | Driver | Link |
| Adafruit | 1.44" | 128 | 128 | 3.3 - 5V | ST7735R | Adafruit 1.44" Color TFT LCD Display |
| Adafruit | 0.96" | 160 | 80 | 3.3 - 5V | ST7735 | Adafruit 0.96" 160x80 Color TFT Display |
| Adafruit | 1.14" | 240 | 135 | 3.3 - 5V | ST7789 | Adafruit 1.14" 240x135 Color TFT Display |
| Adafruit | 1.28" round | 240 | 240 | 3.3 - 5V | GC9A01A | Adafruit 1.28" 240x240 Round TFT Display |
| Adafruit | 1.3" | 240 | 240 | 3.3 - 5V | ST7789 | Adafruit 1.3" 240x240 Wide Angle TFT LCD Display |
| Adafruit | 1.54" | 240 | 240 | 3.3 - 5V | ST7789 | Adafruit 1.54" 240x240 TFT LCD Display * |
| Adafruit | 1.9" | 320 | 170 | 3.3 - 5V | ST7789 | Adafruit 1.9" 320x170 Color IPS TFT Display |
| Adafruit | 1.47" | 320 | 172 | 3.3 - 5V | ST7789 | Adafruit 1.47" 320x172 Rounded TFT Display |
| Adafruit | 2.0" | 320 | 240 | 3.3 - 5V | ST7789 | Adafruit 2.0" 320x240 Color TFT Display |
* The Universal TFT Display Backpack will also accommodate the latest version of the 1.54" 240x240 display which has a 12-way pin header with an additional TE pin.
Use the 11-way row of pins for Adafruit displays. Note that a couple of Adafruit TFT displays have an incompatible pinout; if you're not sure whether your display is compatible check that it has the following 11-way pin header:
| BL | SDCS | D/C | RST | CS | MOSI | MISO | SCK | GND | 3V3 | VIN |
The Adafruit displays all include an LDO 3.3V regulator and logic-level translation, so can be safely interfaced to processors powered from either 5V or 3.3V. They also include an SD-card socket, and a separate SDCS select line for the SD card; you can connect this to PA6 by fitting a 0Ω resistor in position L1 on the board.
The Universal TFT Display Backpack displaying the BarChart example on
an Adafruit 1.44" 128x128 TFT display.
AliExpress displays
The Universal TFT Display Backpack is also compatible with the following displays available from AliExpress and other Chinese suppliers:
| Supplier | Size | Width | Height | Voltage | Driver | Link |
| AliExpress | 1.44" | 128 | 128 | 3.3 - 5V | ST7735R | 1.44" 128x128 SPI TFT display |
| AliExpress | 0.96" | 160 | 80 | 3.3V | ST7735 | TFT Display 0.96 inch 80x160 |
| AliExpress | 1.8" | 160 | 128 | 3.3V | ST7735R | 1.8" 128x160 SPI TFT Display Blue PCB |
| AliExpress | 1.14" | 240 | 135 | 3.3V | ST7789 | 1.14in SPI 240x135 RGB TFT display |
| AliExpress | 1.28" round | 240 | 240 | 3.3V | GC9A01 | 1.28" 240x240 Round TFT Display Octagonal PCB |
| AliExpress | 1.54" | 240 | 240 | 3.3V | ST7789 | 1.54" 240x240 TFT LCD Display |
| AliExpress | 1.9" | 320 | 170 | 3.3V | ST7789 | 1.9" 170x320 TFT LCD Display |
| AliExpress | 1.47" | 320 | 172 | 3.3V | ST7789 | 1.47" 172x320 Rounded TFT LCD Display |
| AliExpress | 2.4" | 320 | 240 | 3.3V | ILI9341 | 2.4" 320x240 TFT Display Module Blue PCB |
| AliExpress | 2.8" | 320 | 240 | 3.3V | ST7789 | 2.8" 320x240 TFT Display Module Blue PCB ‡ |
| AliExpress | 3.5" | 480 | 320 | 3.3V | ST7796S | 3.5" 480x320 TFT Display Module Blue PCB ‡ |
‡ The Universal TFT Display Backpack will also accommodate these displays that have a 9-way pin header with an additional SDA-0 pin.
Use the 8-way row of pins for AliExpress displays. To ensure that your display is compatible, check that it has the following 8-way pin header:
| GND | VCC | SCL | SDA | RES | DC | CS | BLK |
Some of the AliExpress displays include a LDO 3.3V regulator, but none of them include logic-level translation, so I recommend only interfacing them to a processor running from 3.3V.
Display header pins
The display header pin holes are staggered, with each hole shifted 8 mil (~0.2 mm) off-centre. This allows you to push the display's pin headers in place, and they will stay firmly connected without soldering. To remove them press evenly with a suitable flat object. Of course you also have the option of soldering them if you prefer, for a permanent solution.
Circuit
Here's the circuit of the Universal TFT Display Backpack:
Circuit of the Universal TFT Display Backpack using an ATtiny414.
If you're using an Adafruit display you can power the backpack from 3.3V to 5V, but if you're using an AliExpress display you should use 3.3V.
The 10kΩ pullup resistor on reset is only needed on AliExpress displays; on the Adafruit displays it's included on the board.
Build options
Crystal
If you are using a 1-series or 2-series ATtiny processor, and you want more accurate timing than provided by the main processor clock, you can fit the crystal and associated capacitors.
To calculate the capacitor values I used the formula C = 2(CL - CS), where CL is the load capacitance 6pF, and CS is the stray capacitance which is usually estimated to be 2.5pF on a PCB. This gives C=7pF. I used the closest available value, 6pF.
Temperature sensor
The board also includes space for an MCP9808 temperature sensor in an MSOP-8 package. This is an I2C digital temperature sensor with a typical accuracy of ±0.25°C over the sensor's -40°C to +125°C range, and a precision of 0.0625°C. If you are not fitting the temperature sensor you can also omit the two 10kΩ pullup resistors on SDA and SCL. The temperature sensor has an I2C address of 0x18.
Spare I/O pins
The two spare I/O spare pins, PA5 and PA6, are taken to the edge connector pins D1 and D2.
The board also includes spaces for four 0Ω resistors to act as links L1 to L4 to select the following functions of these pins:
- L1 connects PA6 to the SDCS pin for use with Adafruit displays that include an SD card socket.
- L2 connects PA5 to the display backlight, to allow you to control the backlight from the program. This supports PWM analogue output, so you can vary the brightness of the backlight from the microcontroller with analogWrite().
- L3 connects PA6 to the TE (Tearing Effect) output pin, available on some Adafruit displays, to synchronise graphics with the display refresh to avoid flicker.
- Alternatively L4 connects PA5 to the TE (Tearing Effect) output pin. Only fit one of L3 and L4.
For most applications I recommend fitting 0Ω resistors in L1 and L2 only.
Here's the parts list (click to expand):
Parts list
| Qty | Item | Value | Size | Typical parts |
| 3 | SMD resistor | 10kΩ | 0805 | Yageo RC0805JR-0710KL |
| 2 | SMD resistor | 0Ω | 0805 | Yageo RC0805JR-070RL |
| 2 | Ceramic capacitor | 6pF | 0805 | Murata GQM2195C2E6R0CB12D |
| 1 | Ceramic capacitor | 0.1µF | 0805 | Yageo CC0805KRX7R8BB104 |
| 1 | Microcontroller | ATtiny814 | SOIC 14-pin | ATTINY814-SSN |
| 1 | Temperature sensor | MCP9808 | MSOP-8 | MCP9808T-E/MS |
| 1 | Crystal | 32.768kHz | 3.2 x 1.5mm | ABS07-120-32.768kHz-T |
| 1 | PCB | Double-sided | 35.6 x 18.2mm |
Construction
I designed a PCB in Eagle and sent it to PCBWay for production. There's a link at the end of the article you you want to make yourself some boards.
I used a Miniware MHP50-B5 50x50mm hotplate [1] [2] at 235°C with Chip Quik SMD291AX10T3 solder paste to solder the board, but if you don't have a hotplate or hot air gun you should be able to solder the SMD components with a bit of care using a fine-tipped soldering iron and fine solder.
The assembled Universal TFT Display Backpack board.
Using the TFT Display Backpack
Fitting the display
- To use the backpack with one of the compatible Adafruit displays push-fit the display pins into the lower row of 12 holes, aligning the VCC pin on the display with the rightmost hole.
- To use the backpack with one of the compatible AliExpress displays push-fit the display pins into the upper row of 9 holes, aligning the GND pin on the display with the leftmost hole.
Tiny TFT Graphics Library
The Universal TFT Display Backpack is ideal for use with my Tiny TFT Graphics Library 2, which is optimised for use with ATtiny microcontrollers such as the ATtiny814.
To adapt the library to the different pin position of the CS pin on the ATtiny814, edit the assignments at the top of the program to:
// ATtiny402/412 PORTA positions. Change these for the chip you're using int const dc = 7; int const mosi = 1; int const sck = 3; int const cs = 4;
Compact TFT Graphics Library
You could also use my Compact TFT Graphics Library which uses standard Arduino SPI routines.
Edit the assignments at the top of the program to:
// Arduino pin numbers. Change these for your display connections int const cs = PIN_PA4; // TFT display SPI chip select pin int const dc = PIN_PA7; // TFT display data/command select pin
In this case these are Arduino pin numbers, not port positions, so the simplest thing is to use the PIN definitions as above.
Backlight
If you've fitted a 0Ω resistor in position L2 you can use PA5 (Arduino pin 1) to control the display backlight. For example, to dim the backlight to half brightness:
analogWrite(PIN_PA5, 127);
On some AliExpress displays the backlight is off by default, so you won't see anything. To turn the backlight on add the following line in setup():
analogWrite(PIN_PA5, 255);
Crystal and temperature sensor
I'll give some examples of using the crystal and temperature sensor in future projects.
Compiling the graphics library
Compile the program using Spence Konde's megaTiny Core on GitHub. Choose the ATtiny3224/1624/1614/1604/824/814/804/424/414/404/241/204 option under the megaTinyCore heading on the Board menu.
- Check that the subsequent options are set as follows (ignore any other options):
Chip: "ATtiny814" (or as appropriate)
Clock: "20 MHz internal"
To program the processor the recommended option is to use a 3.3V USB to Serial board, such as the SparkFun FTDI Basic board [3], or a USB to Serial cable [4], connected with a Schottky diode as follows. You can substitute a 4.7kΩ resistor for the Schottky diode:
- Set the Programmer option to "SerialUPDI (230400 baud)".
- Upload the program.
Both graphics libraries include a number of example programs that you can use the test the Universal TFT Display Backpack.
Resources
Universal TFT Display Backpack
Get the Eagle files for the PCB here: https://github.com/technoblogy/universal-tft-display-backpack-2.
Or order boards from OSH Park here: Universal TFT Display Backpack 2.
Graphics libraries
Here's the Tiny TFT Graphics Library and examples: Tiny TFT Graphics Library Program.
Here's the Compact TFT Graphics Library and examples: Compact TFT Graphics Library Program.
- ^ MHP50-B5 on Adafruit.
- ^ MHP50-B5 on AliExpress.
- ^ SparkFun FTDI Basic Breakout - 5V on Sparkfun.
- ^ FTDI Serial TTL-232 USB Cable on Adafruit.
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