I ordered in a 5″ TFT LCD with resistive touch screen, along with Adafuit’s RA8875 Driver Board for 40-pin TFT Touch Displays. These are just some notes and comments of my experience in getting it all working.
Making the connections.
First thing to make clear is that the driver board from Adafruit DOES have level shifting on it, and can be connected to both 3.3V and 5V systems. Let me also be clear that although it will work with a mixture of voltage signals (as I found out), you should PICK ONE.
Connections:
- Vin: +3.3V (** OR +5V)
- GND: GND
- 3Vo: NC (** 3.3V out from the on-board regulator)
- Lite: NC (** Can be used to turn backlight off)
- SCK: SPI SCK
- MISO: SPI MISO (** MISO is NOT tri-stated and cannot be used with other SPI devices without 74HC125 or similar)
- MOSI: SPI MOSI
- CS: SPI CS
- RST: Active Low – connect to any available MCU pin
- WAIT: Active Low – connect to any available MCU pin
- INT: Active Low – connect to any available MCU pin (** or INT pin if you want to use interrupts)
- Y+: NC (** Optional, external touch screen controller)
- Y-:NC (** Optional, external touch screen controller)
- X+:NC (** Optional, external touch screen controller)
- Y-:NC (** Optional, external touch screen controller)
Here are the basic connections made for my setup, which includes the RA8875 driver board, a PIC18F46J11 (3.3V) (44-pin TQFP breakout from Adafruit) and an SD/MMC card breakout from Sparkfun. Top right is voltage regulation. 9VDC in, 3.3V out on the left and 5V out on the right. One thing to note here is I had to use a 10K pullup on the MISO of the SD card to get it to work.
