PIC 18LF8720 SPI interface - Crystalfontz 632 dispaly

[Guest]

Im having difficulty using the SPI interface on a PIC18LF8720 to write to a CrystalFontz 632 display.

The 1st thing I notice is the Display data sheet indicates the max clock rate of the SPI_CLK to the display is 18.182 KHz. I measured the clock on PIC output PIN_C3, at approx 375KHz.

The board I'm using with the PIC has a 6 MHz crystal. It is not an option to change the crystal.

Some relavent code includes:

#include <18F8720.H>
#device ADC=10
#include <string.h>
#fuses H4,NOPUT, NOBROWNOUT, NOLVP, NOWRT, WDT
#use delay(clock=24000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)

#define SCL PIN_C3
#define SDA PIN_C4
#define DSPL_BUSY PIN_C1
#define DSPL_SELECT PIN_C2

main ()
{

setup_spi(SPI_MASTER | SPI_H_TO_L | SPI_CLK_DIV_64);

output_low(DSPL_SELECT); // enable display

delay_ms(50);
spi_write(72);
delay_ms(50);
spi_write(69);

while(1){
RESTART_WDT();
}
}

The display does not change when the above code is executed.
Is the setup_spi() function correct?
Can the clock be made to run slower?
If anyone has any experience with this I would greatly appreciate any input.

Thanks
RobS

[PCM programmer]

Can you specify the exact CrystalFontz LCD ?

I went to their web page to try to download the data sheet,
and they have at least two models called the "632".

Here's one "632" LCD:
http://www.crystalfontz.com/products/index-ser.html
Here's another one:
http://www.crystalfontz.com/products/index-usb.html

I realize you're using SPI and those listed above are not SPI,
but rather than having me search their whole website, can you
provide a link to the proper section on their web page ?

[Ttelmah]

Use Timer2 to clock the SPI.
If you select the option SPI_CLK_T2, you can then program timer2, to use a prescaler of 4, which will give you operation at:

24000000/(4*256*2) = 11718.75Hz

375KHz, is correct with your 24Mhz clock, and division by 64.

Best Wishes

[Kenny]

Also, option SPI_H_TO_L is needed - the data has to be valid before
the clock falls, and the clock idle state is high.

Here is the link:
http://www.crystalfontz.com/products/632/632full.pdf
To set spi mode, solder link JPA has to be made (default is RS232)
and JPE has to be made to select 0V to +5V for DATA_IN (default +/-10V).

Here are some other things that need to be right.
From the forum:
" SPI_CS must go low before a the SPI transfer, and ideally will go
high between each byte to guarantee bit synchronization".

Also,
"In almost all cases, SPI_BUSY will stay low. If you experience
trouble and it is going high, you will need to wait for it to go
low before sending the next byte".