The LCD is working perfectly when config the onboard soldering pad to 5v but it doesn't work when config to 3.3v.
I wired the LCD with Arduino like the image
and used the U8glib GraphicsTest code:
#include "U8glib.h"
U8GLIB_ST7920_128X64_4X u8g(13, 11, 10, 8);
void u8g_prepare(void) {
u8g.setFont(u8g_font_6x10);
u8g.setFontRefHeightExtendedText();
u8g.setDefaultForegroundColor();
u8g.setFontPosTop();
}
void u8g_box_frame(uint8_t a) {
u8g.drawStr( 0, 0, "drawBox");
u8g.drawBox(5,10,20,10);
u8g.drawBox(10+a,15,30,7);
u8g.drawStr( 0, 30, "drawFrame");
u8g.drawFrame(5,10+30,20,10);
u8g.drawFrame(10+a,15+30,30,7);
}
void u8g_disc_circle(uint8_t a) {
u8g.drawStr( 0, 0, "drawDisc");
u8g.drawDisc(10,18,9);
u8g.drawDisc(24+a,16,7);
u8g.drawStr( 0, 30, "drawCircle");
u8g.drawCircle(10,18+30,9);
u8g.drawCircle(24+a,16+30,7);
}
void u8g_r_frame(uint8_t a) {
u8g.drawStr( 0, 0, "drawRFrame/Box");
u8g.drawRFrame(5, 10,40,30, a+1);
u8g.drawRBox(50, 10,25,40, a+1);
}
void u8g_string(uint8_t a) {
u8g.drawStr(30+a,31, " 0");
u8g.drawStr90(30,31+a, " 90");
u8g.drawStr180(30-a,31, " 180");
u8g.drawStr270(30,31-a, " 270");
}
void u8g_line(uint8_t a) {
u8g.drawStr( 0, 0, "drawLine");
u8g.drawLine(7+a, 10, 40, 55);
u8g.drawLine(7+a*2, 10, 60, 55);
u8g.drawLine(7+a*3, 10, 80, 55);
u8g.drawLine(7+a*4, 10, 100, 55);
}
void u8g_triangle(uint8_t a) {
uint16_t offset = a;
u8g.drawStr( 0, 0, "drawTriangle");
u8g.drawTriangle(14,7, 45,30, 10,40);
u8g.drawTriangle(14+offset,7-offset, 45+offset,30-offset, 57+offset,10-offset);
u8g.drawTriangle(57+offset*2,10, 45+offset*2,30, 86+offset*2,53);
u8g.drawTriangle(10+offset,40+offset, 45+offset,30+offset, 86+offset,53+offset);
}
void u8g_ascii_1() {
char s[2] = " ";
uint8_t x, y;
u8g.drawStr( 0, 0, "ASCII page 1");
for( y = 0; y < 6; y++ ) {
for( x = 0; x < 16; x++ ) {
s[0] = y*16 + x + 32;
u8g.drawStr(x*7, y*10+10, s);
}
}
}
void u8g_ascii_2() {
char s[2] = " ";
uint8_t x, y;
u8g.drawStr( 0, 0, "ASCII page 2");
for( y = 0; y < 6; y++ ) {
for( x = 0; x < 16; x++ ) {
s[0] = y*16 + x + 160;
u8g.drawStr(x*7, y*10+10, s);
}
}
}
void u8g_extra_page(uint8_t a)
{
if ( u8g.getMode() == U8G_MODE_HICOLOR || u8g.getMode() == U8G_MODE_R3G3B2) {
/* draw background (area is 128x128) */
u8g_uint_t r, g, b;
b = a << 5;
for( g = 0; g < 64; g++ )
{
for( r = 0; r < 64; r++ )
{
u8g.setRGB(r<<2, g<<2, b );
u8g.drawPixel(g, r);
}
}
u8g.setRGB(255,255,255);
u8g.drawStr( 66, 0, "Color Page");
}
else if ( u8g.getMode() == U8G_MODE_GRAY2BIT )
{
u8g.drawStr( 66, 0, "Gray Level");
u8g.setColorIndex(1);
u8g.drawBox(0, 4, 64, 32);
u8g.drawBox(70, 20, 4, 12);
u8g.setColorIndex(2);
u8g.drawBox(0+1*a, 4+1*a, 64-2*a, 32-2*a);
u8g.drawBox(74, 20, 4, 12);
u8g.setColorIndex(3);
u8g.drawBox(0+2*a, 4+2*a, 64-4*a, 32-4*a);
u8g.drawBox(78, 20, 4, 12);
}
else
{
u8g.drawStr( 0, 12, "setScale2x2");
u8g.setScale2x2();
u8g.drawStr( 0, 6+a, "setScale2x2");
u8g.undoScale();
}
}
uint8_t draw_state = 0;
void draw(void) {
u8g_prepare();
switch(draw_state >> 3) {
case 0: u8g_box_frame(draw_state&7); break;
case 1: u8g_disc_circle(draw_state&7); break;
case 2: u8g_r_frame(draw_state&7); break;
case 3: u8g_string(draw_state&7); break;
case 4: u8g_line(draw_state&7); break;
case 5: u8g_triangle(draw_state&7); break;
case 6: u8g_ascii_1(); break;
case 7: u8g_ascii_2(); break;
case 8: u8g_extra_page(draw_state&7); break;
}
}
void setup(void) {
// flip screen, if required
//u8g.setRot180();
#if defined(ARDUINO)
pinMode(13, OUTPUT);
digitalWrite(13, HIGH);
#endif
}
void loop(void) {
// picture loop
u8g.firstPage();
do {
draw();
} while( u8g.nextPage() );
// increase the state
draw_state++;
if ( draw_state >= 9*8 )
draw_state = 0;
// rebuild the picture after some delay
//delay(150);
}
I connect the LCD based on this video to make it work with serial data, so there are no data pins needed. When the LCD's soldering pads are changed to 5v, the screen will show and work correctly but when I change to 3.3v, it doesn't show anything but the backlight is still working.
Which arduino are you using? The Mega shown in your diagram has 5V logic.
Yes, I'm using the Arduino Mega and the wire are connected like in the diagram.
Then can you explain why you want to run the display at 3.3V? You are likely to damage the display with the 5V signals from the Mega.
I want to run the display at 3.3v because the raspberry pi pico only has a 3.3v pin, I already change the soldering pad to 3.3v like the diagram and connect to 3.3v but the display doesn't work, when I change the soldering pad to 5v again and connect to 5v it working again.
Does the display work at 3.3V when connected to the pi pico?
The display doesn't show any sign of working when connected to 3.3v.
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