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tienchuan
Joined: 25 Aug 2009
Posts: 175
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| Problems LCD16x02 with 74HC595. |
 Posted: Mon May 23, 2016 3:34 am |
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Hi everybody.
Im redesign a project with LCD 16x02 (HD44780) followed this links:
http://www.electronics-lab.com/project/3-wire-serial-lcd-using-a-shift-register/
Because Im using 3.3V power supply for MCU, sothat I feed a 3.3V for 74HC595 and LCD power supply pin.
I read the datasheet of both LCD and 74HC595 can operatings with 3.3V.
I tried port code from MicroC to CCS, but the result LCD display not clear, I also tried tie VEE to GND, but LCD display not brightness.
If can, pls help me to solve this problem.
Thanks you.
* driver 74595_lcd_ex.c
| Code: |
#define lcd_en PIN_B4
#define lcd_data_595 PIN_B5
#define lcd_clk_595 PIN_B6
void init_74595_lcd(void)
{
output_low(lcd_data_595);
output_low(lcd_clk_595);
}
void write_nibble_lcd(unsigned int data, unsigned int1 rs)
{
unsigned int j=0, tmp=0;
output_high(lcd_en);
delay_us(20);
//------------ write RS ------------------
output_bit(lcd_data_595,RS);
output_low(lcd_clk_595);
delay_us(10);
output_high(lcd_clk_595);
delay_us(10);
output_low(lcd_clk_595);
//-------------- write niblle --------------
for(j=0;j<4;j++)
{
tmp= data&(0x08>>j);
if(tmp==0) output_low(lcd_data_595);
else output_high(lcd_data_595);
output_low(lcd_clk_595);
delay_us(10);
output_high(lcd_clk_595);
delay_us(10);
output_low(lcd_clk_595);
delay_us(10);
}
//--------------- write lacth-----------------
output_high(lcd_clk_595);
delay_us(10);
output_low(lcd_clk_595);
delay_us(10);
//--------------- reset signal----------------
output_low(lcd_en);
delay_ms(1);
output_high(lcd_en);
delay_ms(1);
output_low(lcd_data_595);
}
void write_byte_lcd(unsigned int data, unsigned int1 RS)
{
unsigned int hi_byte, lo_byte;
hi_byte= (data>>4)&0x0F;
lo_byte= data&0x0F;
write_nibble_lcd(hi_byte,RS);
write_nibble_lcd(lo_byte,RS);
}
void init_lcd(void)
{
init_74595_lcd();
output_low(lcd_en);
delay_ms(100);
//! write_byte_lcd(0x20,0); delay_ms(50);
write_byte_lcd(0x20,0); delay_ms(50);
write_byte_lcd(0x20,0); delay_ms(50);
write_byte_lcd(0x20,0); delay_ms(50);
write_byte_lcd(0x28,0); delay_ms(50);
write_byte_lcd(0x0E,0); delay_ms(50);
write_byte_lcd(0x06,0); delay_ms(50);
write_byte_lcd(0x01,0); delay_ms(50);
delay_ms(1000);
}
void home_lcd(void)
{
write_byte_lcd(0x02,0);
delay_ms(10);
}
void move_lcd(unsigned int y, unsigned int x)
{
unsigned int addr;
addr= 64*(y-1)+(x-1)+0x80;
write_byte_lcd(addr,0);
}
void clr_lcd(void)
{
write_byte_lcd(0x01,0);
delay_ms(10);
}
void putchar_lcd(unsigned char schar)
{
write_byte_lcd(schar,1);
delay_ms(1);
}
void putstring_lcd(char* str, unsigned char len)
{
unsigned char i;
for(i=0;i<len;i++)
{
if(str[i]>0) putchar_lcd(str[i]);
else putchar_lcd(' ');
}
}
|
* Main code
| Code: |
#include <18F2520.h>
#fuses HS
#fuses PUT
#fuses NOFCMEN
#fuses NOIESO
#fuses NOPBADEN
#fuses MCLR
#fuses NOSTVREN
#fuses NOXINST
#fuses NODEBUG
#fuses PROTECT
#fuses NOLVP
#fuses NOWDT
#fuses NOBROWNOUT
#fuses NOXINST
#use delay(clock=16000000)
//!#include "lcd16x2.c"
#include "74595_role.c"
#include "74595_lcd_ex.c"
void main(void)
{
Delay_ms(1000);
set_tris_b(0);
output_high(PIN_B7);
output_toggle(PIN_B2);
delay_ms(200);
output_toggle(PIN_B2);
delay_ms(200);
output_toggle(PIN_B2);
delay_ms(200);
output_toggle(PIN_B2);
delay_ms(200);
init_lcd();
clr_lcd();
putchar_lcd('A');
putchar_lcd('A');
putchar_lcd('A');
putchar_lcd('A');
while(1)
{
}
}
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temtronic
Joined: 01 Jul 2010
Posts: 9225
Location: Greensville,Ontario
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| Posted: Mon May 23, 2016 5:21 am |
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A couple of points...
I just opened the 18F2520 datasheet, looked at chapter 26, 'electrical characteristics', figure 26-1 and the lowest Vdd is 4.2 volts NOT '3 volts'.
Now if you're using the 18LF2520, that will run at 3 volts.
If you need to run at 3 volts you WILL need the 'L' version of that PIC or an F version designed to run at 3 volts( few do but 18F46K22 is one !)
...however you have another problem..
Most ( all ?) common 16x2 LCD module require to be run from 5 volts. 3 volt rated ones are few and expensive !
I have a simple hardware solution that WILL allow you to run a 5 volt LCD module from 3 volts though. It's been benched tested for the past 3 months and is stable.The required hardware consists of 2 diodes and 2 capacitors, to form a voltage doubler and one PIC I/O pin. Software consists of using the timer associated with that pin. The program simply sets up the timer to run at a few KHz, 50% duty cycle..more or less.
In my case it runs a 20x4 LCD module to display 4 BIG digits for a tachometer project. Of course now that planting season is here,I'm out there not 'playing with PICs.
Jay |
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tienchuan
Joined: 25 Aug 2009
Posts: 175
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| Posted: Mon May 23, 2016 7:51 pm |
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| temtronic wrote: | A couple of points...
I just opened the 18F2520 datasheet, looked at chapter 26, 'electrical characteristics', figure 26-1 and the lowest Vdd is 4.2 volts NOT '3 volts'.
Now if you're using the 18LF2520, that will run at 3 volts.
If you need to run at 3 volts you WILL need the 'L' version of that PIC or an F version designed to run at 3 volts( few do but 18F46K22 is one !)
...however you have another problem..
Most ( all ?) common 16x2 LCD module require to be run from 5 volts. 3 volt rated ones are few and expensive !
I have a simple hardware solution that WILL allow you to run a 5 volt LCD module from 3 volts though. It's been benched tested for the past 3 months and is stable.The required hardware consists of 2 diodes and 2 capacitors, to form a voltage doubler and one PIC I/O pin. Software consists of using the timer associated with that pin. The program simply sets up the timer to run at a few KHz, 50% duty cycle..more or less.
In my case it runs a 20x4 LCD module to display 4 BIG digits for a tachometer project. Of course now that planting season is here,I'm out there not 'playing with PICs.
Jay |
Hi.
Thanks for your helping.
Because in my project using BLE RN4020 module to interface with MCU sothat I choosing a 3.3V is power supply.
In last time, I tried connected LCD direct with PIC18F97J60 with 3.3V and it run ok, so i think when i change to this design, adding 74HC595IC to reduce pin MCU, the result not good.
Im very happy if you can share me more about your design above.
And I think I change to LCD 3.3 to tried it before.
Thanks you.
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