I have been fighting undesired artifacts (':oops:') on a T6963C based LCD and can't get a handle on it. I am reaching out for help, primarily a sanity check
. In the course I have written a short program for an PIC24HJ256GP210 MCU. If anyone would like to try to reproduce what I see and confirm, would be great. If it can't be reproduced then I might have to look for another LCD although I am convinced that it is not the piece of hardware. What I see is that initially the screen is drawn correctly (but I have also seen mishaps at first draw totally at random 
) and after a few repetitions the screen gets messed up. Sometimes, LCD commands don't make it and parts of Graphics memory get messed up too.Here is the code:
Code: Select all
/****************************************************************************************
*** This short application produces an irregular behavior by not printing certain ****
*** Text then again it does and messing up the Graphical box (white) ****
*** It seems as if text ROM Data is bleeding or misrouted into RAM ? ****
*** Some LCD commands are simply not executed ****
*** I had the LCD setup directly to 3.3V and using a 3.3V to 5V translator ****
*** with the same results. ****
*** The LCD is a CrystalFontz CFAG240128L-STI-TZ Monochrome 240x128 device ****
*** LCD setup times (various) are according to Spec Sheet between 10-100nS ****
*** Furthermore the input(min) high voltage is VDD-2.2 V i.e. 5-2.2 = 2.8 V ****
*** If run on 3.3 > 2.8 Volt the high level is fully satisfied unless reshaped ****
*** by stray Capacitance. It's got to be quiet some Capacitor ****
*** The input low voltage is between 0.3 and 0.8 (max) Volts. ****
*** I did try several different LCD's of same model, all got messed up ****
*** therefore I don't believe that the Hardware has a problem ****
****************************************************************************************/
// The MCU used for this application is a PIC24HJ256GP210 with external Crystal at 16MHz
#include "T6963C.h"
unsigned long clk;
char txt[5];
void puts(char *msg, int pos, int lin);
void bottom_menu(char *msg);
void cls() {
T6963C_panelFill(0);
}
void bottom_menu(char *msg) {
T6963C_WRITE_TEXT(msg, 1, 15, T6963C_ROM_MODE_XOR);
}
void DispOn() {
char text[] = "Error!";
T6963C_waitready();
puts(text, 1, 0);
puts(text, 15, 0);
puts(text, 30, 0);
T6963C_waitready();
puts(text, 1, 5);
puts(text, 15, 5);
puts(text, 30, 5);
T6963C_waitready();
puts(text, 1, 10);
puts(text, 15, 10);
puts(text, 30, 10);
}
void DispOff() {
T6963C_waitready();
puts(" ", 1, 0);
puts(" ", 1, 5); // 39 Chars of 0x20
puts(" ", 1, 10);
T6963C_waitready();
}
void init_app() {
/* below will set MCU for 80MHz - 40Mips with 16MHz external Crystal */
/* 16MHz / 2 = 8MHz -- 8MHz * 20 = 160 MHz -- ouput 160 MHz / 2 = 80 MHz */
CLKDIV = 0x0000; // Divide input by 2 and divide output by 2
PLLFBD = 0x0012; // Multiply FCY by 20
/* Comment the above and set project to 16MHz to try it at slower speeds
don't forget the Project to change to FNOSC_PRI */
AD1PCFGL = 0xFFFF; /* Disable ADC module */
AD1PCFGH = 0xFFFF; /* Disable all ADC channels */
TRISA = 0x0000; /* Configure PORTA as digital outputs */
}
void puts(char *msg, int pos, int lin) {
T6963C_WRITE_TEXT(msg, pos, lin, T6963C_ROM_MODE_XOR);
}
// Display gets messed up with only those few instruction at Base clock 16MHz
void main() {
init_app();
LATBbits.LATB13 = 1; // Sets the Font Select Bit to 6x8
/* LCD connected to
PORTB(L) "data" --
PORTB(H) "control" Pin 8 = /WR Pin 9 = /RD Pin 11 = C/D Pin12 = RST
this would be the 128x64 adapter with the reverse display select to ground */
T6963C_init(240, 128, 6, &PORTB, &PORTB, 8, 9, 11, 12);
T6963C_text(1);
// Also observe screen while Graphics is disabled
T6963C_graphics(1); // Important --- Less likely to fail if Text only selected
cls();
T6963C_box(0, 119, 239, 127, T6963C_WHITE);
T6963C_box(0, 0, 239, 7, T6963C_WHITE);
bottom_menu("DIM APRS LIST GPS");
clk = Clock_Khz();
clk = clk / 1000;
if(clk > 16) {
LongToStr(clk, txt); // Get the clock in kHz and convert to MHz
puts(txt, 20, 15);
puts("MHz PLL", 32,15);
}
else {
LongToStr(clk, txt); // Get the clock in kHz and convert to MHz
puts(txt, 20, 15);
puts("MHz", 32,15);
}
/* just loop around */
while(1) {
DispOn();
delay_ms(500);
DispOff();
delay_ms(250);
}
}
/*~ Pretty much messed up at Dynamic refreshes */This code is complete, compiles and runs if connected correctly.
Anyone interested?
