Problem with LCD and Start Up

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- 19th October 2006, 12:06
savnik

Problem with LCD and Start Up

I have a problem with below code and i don't know how to solve it.
When start the power on all works ok.But if power of for 1-3 sec and again power on the LCD show chinese and the program not work.If the power of is largest from 3 secs all works ok.
The pic is 16f84a.

Code:

DEFINE LCD_DREG PORTB 'Selection of the port B DEFINE LCD_DBIT 0 'Selection one RB0 with RB3 DEFINE LCD_RSREG PORTA 'RS on port A DEFINE LCD_RSBIT 2 'RS on RA2 DEFINE LCD_EREG PORTA 'E on port A DEFINE LCD_EBIT 3 'E on RA3 DEFINE LCD_BITS 4 'Mode 4 bits DEFINE LCD_LINES 2 '2 lines DEFINE I2C_SCLOUT 1 ' ** DEFINITION OF THE ENTREES - EXITS ' Exits I2C SCL var PORTA.1 ' SCL on RB1 (pine 18) SDA var PORTA.0 ' SDA on RB0 (pin 17) ' Boutons UP var PORTB.6 'increase the frequency (on RB6) DOWN var PORTB.7 'decrease the frequency (on RB7) CH_PAS var PORTB.5 'Change the step of synth (on RB5) Input UP 'Up and Down are entries Input DOWN Input CH_PAS ' ** DECLARATION OF THE VARIABLES b1 var Byte b2 var Byte b3 var Byte b5 var Byte F1 var Word F2 var Word F3 var Word ADDR1 VAR Byte ADDR2 VAR Byte LOCK VAR Byte BAND VAR BYTE TMP VAR WORD TMP_LO VAR TMP.LOWBYTE TMP_HI VAR TMP.HIGHBYTE PLLBASE VAR WORD PLL VAR WORD RXPLL VAR WORD LO VAR RXPLL.LOWBYTE HI VAR RXPLL.HIGHBYTE PAS VAR BYTE '1=125kHz, 2=250kHz, 4=500kHz, 8=1MHz '*** INITIAL DATA *** ADDR1=$C2 ADDR2=$C3 'adress I2C of SDA5055 (ADDR1=$C0 , adress I2C of TSA5511) PLLBASE=720 'beginning with 45 MHz : 45 / 0,0625 = 720 PAS = 2 'pas of 0.0625 MHZ by defect PAUSE 100 LCDOUT $FE, 1 ' Clear LCD screen LCDOUT "TUNER 45-890 MHZ" ' post text during 2 second PAUSE 1000 EEPROM 0,[$70,$1c] 'initial data TMP =7280 ($1C70) corresponds to F = 500 MHz
- 19th October 2006, 12:18
mat janssen

After defining the lcd you must place a pause of about 500 msec.
This is nessesary to give the lcd a chanche to setup and set all registers insite ok, before receiving de lcd data for the screen.
- 19th October 2006, 12:39
savnik

Quote:

Originally Posted by mat janssen

After defining the lcd you must place a pause of about 500 msec.
This is nessesary to give the lcd a chanche to setup and set all registers insite ok, before receiving de lcd data for the screen.

I have test this :
Pause 250 ' Delay for LCD to power up
and this :
Pause 1000 ' Delay for LCD to power up
but nothing.
The problem is the same.
I understand , that my problem is the reset on pin 4 (i test 4.7k-10k-33k)
If i delay the reset on pin 4 for 4 and up secs all work ok.
- 19th October 2006, 19:58
savnik

if at the top of code before define add the follow code

Code:

pause 2000 @ reset

it's ok
- 20th October 2006, 06:46
amindzo

Hi,
please try this:

' Set LCD Data port
DEFINE LCD_DREG PORTB
' Set starting Data bit (0 or 4) if 4-bit bus
DEFINE LCD_DBIT 4
' Set LCD Register Select port
DEFINE LCD_RSREG PORTB
' Set LCD Register Select bit
DEFINE LCD_RSBIT 1
' Set LCD Enable port
DEFINE LCD_EREG PORTB
' Set LCD Enable bit
DEFINE LCD_EBIT 0
' Set LCD bus size (4 or 8 bits)
DEFINE LCD_BITS 4
' Set number of lines on LCD
DEFINE LCD_LINES 2
pause 100
lcdout $fe,1,"Hello"
end

LCD Connection
Pin1=Vss: connect to ground
Pin2=Vdd: connect to Vcc=5V
Pin3=Vo: connect to middle pin of the POT(20K) to control brightness
Pin4=RS(register select): connect to micro pins that specify in the software(RB1)
Pin5=RW(Read/Write): connect to ground because we want to only write
Pin6=E(Enable): connect to micro pin that specify in the software(RB0)
Pin7 to 10: No connection
Pin 11 to 14: connect to RB4 to RB7
Pin15: connect to Vcc with a resistor(100 or 200 ohm resistor is good)
Pin16: connect to ground.
pin 16 and pin 16 are for backlights

the other two pins of pot should connect to VCC and ground and you should connect the MCLR with a 4.7K or 10K resistor to the VCC.

if your problem is not solve with this program you have another problem in other parts.
- 20th October 2006, 07:08
savnik

thank you for answer , but i have make the circuit on pcb and i can't make changes
- 20th October 2006, 13:23
mister_e

be sure you set LVP to OFF, BOD to ON, PWRT to ON in your config fuses.

I doesn't do magic, but it help in most cases.
- 20th October 2006, 17:22
savnik

Quote:

Originally Posted by mister_e

be sure you set LVP to OFF, BOD to ON, PWRT to ON in your config fuses.

I doesn't do magic, but it help in most cases.

My pic is 16f84a not pic16F628a
- 20th October 2006, 18:53
paul borgmeier

Paul's Theory - It sure sounds like to me that during the 0-3 second period after you turn off the power (and before you turn it on again), the power supply voltage drops low enough to reset the pic but not low enough to reset the LCD. After 4 seconds off, I am guessing the voltage decays enough to reset the processor AND the LCD - the LCD might be in the brown area until 4 seconds passes. You can:

1)Use a scope to measure the voltage after you turn off the power and see what it does.
2)Reset the LCD in software as partially described earlier in the week here
http://www.picbasic.co.uk/forum/showthread.php?t=4851
3)Change your power supply so that the voltage decays faster when the power is removed.
4) Board change – move the power for the LCD (not backlight if you have one) to an open pin on the PIC and control it there. (I know your board is does but ... if you need to make a change later)

Quote:

the LCD show chinese

Oh, I am guessing it is japanese you are seeing and not chinese :) - most controllers have japanese as a second set of data characters built in.

Just my 2 cents worth
- 20th October 2006, 22:08
mister_e

chinese or japanese, it's greek to me :D
- 20th October 2006, 22:23
savnik

Quote:

Originally Posted by mister_e

chinese or japanese, it's greek to me :D

maybe japanese
- 21st October 2006, 11:04
savnik

1 Attachment(s)

now work

I change the pic16f84a with 16f628a and now work OK
why this difference;
my config is
- 21st October 2006, 19:25
mister_e

Brown out detect is the answer.

Maybe the power-up timer could help on your grandpa F84. But more than likely, a capacitor between MCLR and gnd will work... have a look to the F84 datasheet. i'm pretty sure they show you some RESET circuit there.

It's no coincidence why most PIC have a Brown-Out detect feature now :D

I usually set both to ON
- 21st October 2006, 20:22
savnik

Quote:

Originally Posted by mister_e

Maybe the power-up timer could help on your grandpa F84.

I test but no help.

Quote:

Originally Posted by mister_e

a capacitor between MCLR and gnd will work

I have capacitor.

The only solution for me is to replace the 16f84a with 16f628a , or to use a MCP100-101