The RFzero library supports a number of displays and protocols. If you want to use a different display or protocol, you will have to integrate this yourself. If you can find others who have done it before for an Arduino or even better for the Arduino Zero, you will have a good start.

The supported displays and display modes.

Display	Mode	Protocol	Wires	Extra hardware	Type	Resolution
None	0
HD44780 16x2	1	4 bits parallel	12		Character	16 characters x 2 lines
HD44780 20x4	2	4 bits parallel	12		Character	20 characters x 4 lines
HD44780 16x2	3	I2C	4	PCF8574 module	Character	16 characters x 2 lines
HD44780 20x4	4	I2C	4	PCF8574 module	Character	20 characters x 4 lines
ILI9341	5	SPI (no parallel)	8		Graphic	320 pixels x 240 pixels (4:3)
ILI9488	6	SPI (no parallel)	8		Graphic	480 pixels x 320 pixels (3:2)

Please remember that if you use display mode 3 or 4, and don’t have the necessary pull-up resistors in place your RFzero is likely to freeze. This is not an RFzero thing but a general issue with Arduino. If it does happen please see the troubleshooting guide. You also need to set the I2C address of the PCF8574,  PCF8574A or PCF8574T in the configuration. Furthermore, does the adaptor board control the contrast and backlight levels not the RFzero.

Display mode 1 and 2

Display mode 1 and 2 connections.

Signal	RFzero	Pin	Display	Pin
GND	GND	JP12-1	VSS	1
3V3/VI	3V3/VI	JP12-2	VCC	2
Contrast	Contrast	JP12-3	V0	3
Select registers	D14	JP12-4	RS	4
Read/Write	Write (GND)	JP12-5	R/W	5
Enable	D15	JP12-6	Enable	6
Data 4	D10	JP12-7	DB4 or D4	11
Data 5	D11	JP12-8	DB5 or D5	12
Data 6	D12	JP12-9	DB6 or D6	13
Data 7	D13	JP12-10	DB7 or D7	14
Backlight positive	Backlight positive	JP12-11	Anode	15
Backlight GND	GND	JP12-12	Cathode	16

PCB layout of a typical parallel HD44780 LCD.

LCD voltage jumper

Before you connect any LCD to the LCD header please make sure you have set the correct drive voltage for the LCD on the LCD voltage select header – JP13. Alternatively, if you know that you will always be using one of the voltages you could short the relevant jumper position with a small piece of wire that is soldered in place.

The LCD voltage header JP13.

The LCD voltage set to use VI

Please note that if you run the LCD on the VI level the contrast and backlight will change if the VI is changed.

The LCD voltage set to use 3,3 V (3V3).

Display mode 2 and 4

Display mode 3 and 4 connections.

Signal	RFzero	Pin	PCF8574	Display	Pin
GND	GND	JP11-1	VSS	VSS	1
3V3	3V3	JP11-2	VDD	VDD	2
SDA	D8	JP11-3	SDA
SCL	D9	JP11-4	SCL
Contrast				VO	3
Register select			P4	RS	4
Read/write			P5	R/W	5
Enable			P6	Enable	6
Data 4			P0	DB4	11
Data 5			P1	DB5	12
Data 6			P2	DB6	13
Data 7			P3	DB7	14
Backlight positive				Anode	15
Backlight GND				Cathode	16

I2C addresses for the PCF8574 variants.

A2	A1	A0	PCF8574	PCF8574A	PCF8574T
GND	GND	GND	0x20	0x38	0x20
GND	GND	3V3	0x21	0x39	0x21
GND	3V3	GND	0x22	0x3A	0x22
GND	3V3	3V3	0x23	0x3B	0x23
3V3	GND	GND	0x24	0x3C	0x24
3V3	GND	3V3	0x25	0x3D	0x25
3V3	3V3	GND	0x26	0x3E	0x26
3V3	3V3	3V3	0x27	0x3F	0x27

Example of a PCF8574T module.

Display mode 5 and 6

Display mode 5 and 6 connections.

Signal	RFzero	Pin	Display	Pin
3V3	3V3	3V3	VCC	1
GND	GND	GND	GND	2
Chip select	D10	JP11-5	CS	3
Reset	D11	JP11-6	RESET	4
Register/data selection	D12	JP11-7	DC or DC/RS	5
MOSI	D18	JP10-5	SDI, MOSI or SDI (MOSI)	6
SCK	D19	JP10-6	SCK	7
Backlight	3V3	3V3	LED	8
MISO (currently not used)	D16	JP10-3	SDO (MISO)	9

Example of an ILI9341 TFT display.