Programming SPI LCD Switch

Other Hardware Displays
1

Please remove

2

Hi flukey

From a quick look at the datasheet ...

1 GND - (internally connected to SS/CS) - I have plugged this into the Arduino GND
2 VCC- connected to 1k resistor - connected to pin 5

I think VCC can connect directly to +5V - no series resistor required.

3 CLK - Plugged into Arduino 52
4 Data (MISO/MOSI (SISO?) - Plugged into Arduino 50

CLK should go to Mega SCK - pin 52 is right.
DATA should go to Mega MOSI (master out, slave in) - that is pin 51.

int gndPin = GND //Probably not needed or incorrect
int vccPin = 5V //Probably not needed or incorrect
int clkPin = 52
int datPin = 50
int swtPin = A0

The SPI library defines the pins you need - no need for these declarations.

SPI.setClockDivider(SPI_CLOCK_DIV4);  // set up arduino to 4mhz clock speed = match Q5 clock speed as per pdf
SPI.setDataMode(SPI_MODE0);  // Please let me know what this should be 0,1,2,3
SPI.setBitOrder(LSBFIRST); // either LSBFIRST or MSBFIRST

Bit order should be MSBFIRST. I think the data mode is SPI_MODE2.

You need to add this at the start of setup()

SPI.begin();

To test the SPI connection, you could convert just one part of the sample code to Arduino, for example, this backlight setting code.

SPIOut(0x42) ;                       // cmd 0x42 writes backlight with red, green and blue
SPIOut(R) ;                            // value red max 0x7F
SPIOut(G) ;                           // value green max 0x7F
SPIOut(B) ;                            // value blue max 0x7F
SPIOut(0x43) ;                       // value for end of command is 0x43

Since the switch does not use a slave select pin, you just need to convert each SPIOut statement to SPI.transfer() statements. For example:

SPI.transfer(0x42);
SPI.transfer(0x7F);
SPI.transfer(0x00);
SPI.transfer(0x00);
SPI.transfer(0x43);

Regards

Ray