Checkerboad pattern on display
I cannot get the S64240C to work. No matter what I do, all I can get to show on the display is a checkerboard pattern. Imagine dividing the display into 4 quadrants. The top-left and bottom-right quadrants have the pixels turned ON and the bottom-left and top-right quadrants have the pixels turned OFF.
I am using the display in parallel mode and I have it connected exactly as shown in the reference schematic (http://displaytech-us.com/pdf/Schematic/S64240C-testerschematic-061020.pdf), except that I have "C86" tied LOW since I am running in 8080 mode.
I have attached the code for my "initialization", "write command", and "write data" routines.
While I cannot successfully set any of the pixels (I always get the checkerboard), I *can* communicate with the display in some ways. For example, I can successfully turn the display ON and OFF by sending a command of 0xAF and 0xAE. Also, if I set the ADC value via the 0xA0 or 0xA1 command, I can successfully read the right value back via the "Status Read" command. I can also successfully change the display's contrast.
But that's about it. I cannot set any individual pixels. I have ripped up and re-wired my connections a couple of times, and I always get the same results.
Finally, I have measured voltages as listed below:
VDD = 3.3v
V0 = 8.74v
V1 = 7.77v
V2 = 6.80v
V3 = 2.00v
V4 = 1.00v
Vout = 12.2v
Does anyone have any ideas? Is it a power issue? Does the checkerboard pattern mean something specific?
Thank you in advance for your help. I'm losing patience over here. :)
Attachment: code.txt (2.0KB)
One more thing ... I can successfully READ pixel values. For example, if I write a "1" to a specific pixel location, I can then read it back as a "1", but the LCD still does NOT actually turn that pixel on. I either get nothing on the LCD at all or the checkerboard pattern. Argh!!
Here's my write/read code:
// write some test data, starting at 0,0
lcd_control(0, 0xB0); // page 0
lcd_control(0, 0x10); // column 0 (2 bytes)
lcd_control(0, 0x00);
lcd_write(0, 0xAA); // 10101010
lcd_write(0, 0x55); // 01010101
lcd_write(0, 0xAA); // 10101010
lcd_write(0, 0x55); // 01010101
lcd_write(0, 0xAA); // 10101010
lcd_write(0, 0x55); // 01010101
lcd_write(0, 0xAA); // 10101010
lcd_write(0, 0x55); // 01010101
// now read it back and output to LEDs
lcd_control(0, 0xB0); // page 0
lcd_control(0, 0x10); // column 0 (2 bytes)
lcd_control(0, 0x00);
lcd_read(1, 0);
Delay_ms(2000);
lcd_read(1, 0);
Delay_ms(2000);
lcd_read(1, 0);
Delay_ms(2000);
lcd_read(1, 0);
Delay_ms(2000);
lcd_read(1, 0);
Delay_ms(2000);
lcd_read(1, 0);
Delay_ms(2000);
lcd_read(1, 0);
Delay_ms(2000);
lcd_read(1, 0);
Delay_ms(2000);
And this is my "lcd_read()" function:
// function to read status or data from the LCD
void lcd_read(unsigned short A0_value, unsigned short whichCS)
{
bits = 0x0017; // 00010111 = RD low, WR high, A0 low, RESET high, CSS high, CSM high
if ( whichCS == 0 )
{
// whichCS = 0, i.e. MASTER (RB0)
bits.B0 = 0;
}
else
{
// whichCS = 1, i.e. SLAVE (RB1)
bits.B1 = 0;
}
if ( A0_value != 0 )
{
bits.B3 = 1;
}
// read the status
TRISD = 0xFFFF; // set PORTD as inputs
Delay_ms(10); // let the PORT settle
PORTB = bits; // 0001X1XX = RD low, WR high, A0 high/low, RESET high, CSS high/low, CSM high/low
Delay_us(1); // slight delay
PORTF = PORTD; // output to LEDs
PORTB = 0x00FF; // all high (i.e. OFF)
Delay_ms(10); // slight delay
TRISD = 0x0000; // set PORTD back to outputs
}
