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LCD trouble (dog-162 with 7036 driver)

 
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romertz



Joined: 03 Oct 2008
Posts: 12
Location: Bogota

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LCD trouble (dog-162 with 7036 driver)
PostPosted: Fri Apr 17, 2009 11:52 am     Reply with quote
Hello all,
I have a circuit that shows data in a lcd...some normal. I have been using a lcd that uses HD44780 driver and using the flex_lcd.c that I found around here. It works without problems using 4 data bits and 3 control bits But for design motives, I had to change the old Lcd to a new one, EA DOGM162S-A from Electronic Assembly that uses ST7036 driver. In over view, they are compatible, except that when I placed it in my circuit, it doesn't do anything. Like it would be turn off. so reading over I found that the driver are compatible but the init sequence. Because this new Lcd requires a contrast set before using it. I inserted the sequence over the flex_lcd library, based on the driver datasheet. But it still doesn't do anything. I have only one Lcd and I don't know if the Lcd is broken or if it's a hardware issue, or if the library is wrong.
Can anyone help me. Some ideas? Thanks in advance. Very Happy

I will put the two inits, the rest of the library is the same, but I have changed the init secuence.
The new:
Code:

//----------------------------
void lcd_init(void)
{
int8 i;

output_low(LCD_RS);

#ifdef USE_LCD_RW
output_low(LCD_RW);
#endif

output_low(LCD_E);

delay_ms(40);

lcd_send_nibble(0x30);   //function set
    delay_ms(5);         
lcd_send_nibble(0x30);   //function set     
    delay_us(50);   
lcd_send_nibble(0x30);   //function set 
    delay_us(50);
lcd_send_nibble(0x020);   //function set     
    delay_us(50);
lcd_send_nibble(0x29);   //function set   
    delay_us(50);                                                               
lcd_send_nibble(0x14);   //internal osc frecuency   
    delay_us(50);
lcd_send_nibble(0x70);   //Contrast set   
    delay_us(50); 
lcd_send_nibble(0x52);   //power/icon/contrast control   
    delay_us(50);
lcd_send_nibble(0x6a);   //follower control                       
    delay_us(50);         
lcd_send_nibble(0x0C);   //display on
    delay_us(50);                     
               
lcd_send_nibble(0x01);   //clear
    delay_ms(5);
lcd_send_nibble(0x06);   //entry mode set
    delay_us(50);       
/*lcd_send_nibble(0x33);
delay_ms(5);                     
lcd_send_nibble(0x32);*/           
/*
for(i=0; i < sizeof(LCD_INIT_STRING); i++)
   {
    lcd_send_byte(0, LCD_INIT_STRING[i]);        //delay_ms(5);
     
    // If the R/W signal is not used, then
    // the busy bit can't be polled.  One of
    // the init commands takes longer than
    // the hard-coded delay of 60 us, so in
    // that case, lets just do a 5 ms delay
    // after all four of them.
    #ifndef USE_LCD_RW
    delay_ms(5);
    #endif
   }  */

}

//----------------------------


The old:

Code:

//----------------------------
void lcd_init(void)
{
int8 i;

output_low(LCD_RS);

#ifdef USE_LCD_RW
output_low(LCD_RW);
#endif

output_low(LCD_E);

delay_ms(15);

for(i=0 ;i < 3; i++)
   {
    lcd_send_nibble(0x03);
    delay_ms(5);
   }

lcd_send_nibble(0x02);

for(i=0; i < sizeof(LCD_INIT_STRING); i++)
   {
    lcd_send_byte(0, LCD_INIT_STRING[i]);

    // If the R/W signal is not used, then
    // the busy bit can't be polled.  One of
    // the init commands takes longer than
    // the hard-coded delay of 60 us, so in
    // that case, lets just do a 5 ms delay
    // after all four of them.
    #ifndef USE_LCD_RW
    delay_ms(5);
    #endif
   }

}

//----------------------------


where,

Code:

int8 const LCD_INIT_STRING[4] =
{
 0x20 | (lcd_type << 2), // Func set: 4-bit, 2 lines, 5x8 dots
 0xc,                    // Display on
 1,                      // Clear display
 6                       // Increment cursor
 };

PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Apr 17, 2009 1:33 pm     Reply with quote
Look at the orginal code. The lcd_send_nibble() function sends the
lower 4 bits of a byte. So, the following code is sending '3'.
Quote:
for(i=0 ;i < 3; i++)
{
lcd_send_nibble(0x03);
delay_ms(5);
}


Here is your code. What are you sending ? You are sending the lower
4-bits of each byte, which is a '0'. You need to change the values below
to 0x03.
Quote:
lcd_send_nibble(0x30); //function set
delay_ms(5);
lcd_send_nibble(0x30); //function set
delay_us(50);
lcd_send_nibble(0x30); //function set
delay_us(50);

The change in delay times is OK. The data sheet for your LCD says so.


Now let's look at the rest of your code:
Quote:
lcd_send_nibble(0x020); //function set
delay_us(50);
lcd_send_nibble(0x29); //function set
delay_us(50);
lcd_send_nibble(0x14); //internal osc frecuency
delay_us(50);
etc.

And here's the original code:
Quote:
for(i=0; i < sizeof(LCD_INIT_STRING); i++)
{
lcd_send_byte(0, LCD_INIT_STRING[i]);

The original code is using the lcd_send_byte() function, but your code
is calling the nibble function. You need to change it so you're sending
bytes.
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