This color display uses SPI to receive image data. That means you need at least 4 pins - clock, data in, tft cs and d/c. If you'd like to have SD card usage too, add another 2 pins - data out and card cs. However, there's a couple other pins you may want to use, let's go through them all!
Both the 1.3" and the 1.54" have this first set of pins, but the labels differ slightly. Where there is a difference, the first listed is 1.3" and the second is 1.54".
- 3-5V / Vin - this is the power pin, connect to 3-5VDC - it has reverse polarity protection but try to wire it right!
- 3V3 / 3V - this is the 3.3V output from the onboard regulator
- Gnd / G - this is the power and signal ground pin
- SCK / CL - this is the SPI clock input pin. Use 3-5V logic level
- SO - this is the SPI MISO (Master In Slave Out) pin, it's used for the SD card. It isn't used for the TFT display which is write-only. It is 3.3V logic out (but can be read by 5V logic)
- SI - this is the SPI MOSI (Master Out Slave In) pin, it is used to send data from the microcontroller to the SD card and/or TFT. Use 3-5V logic level
- TCS / TC - this is the TFT SPI chip select pin. Use 3-5V logic level
- RST / RT - this is the TFT reset pin. Connect to ground to reset the TFT! Its best to have this pin controlled by the library so the display is reset cleanly, but you can also connect it to the Arduino Reset pin, which works for most cases. There is an automatic-reset chip connected so it will reset on power-up. Use 3-5V logic level
- D/C / DC - this is the TFT SPI data or command selector pin. Use 3-5V logic level
- CCS / CC - this is the SD card chip select, used if you want to read from the SD card. Use 3-5V logic level
- Lite / BL - this is the PWM input for the backlight control. It is by default pulled high (backlight on) you can PWM at any frequency or pull down to turn the backlight off. Use 3-5V logic level
The 1.54" display has one more pin!
- TE - This is the Tear Enable pin. It's an output pin that, when configured, will tell you when the display is refreshing. This is helpful to avoid "tear effect" because you can update the display when it's not drawing.
On the 1.3" display, the TE signal is available, but only as a surface mount test pad (the board couldn't fit another pin)