I2C LCD

[Demon]

On my lcd, I adjust contrast with the potentiometer on pin V0.

Robert

[DaveC3]

Without the LCD data sheet I don't think I can help ay more. Looking at the controller data sheet does not tell the whole story. There are different interfaces and component combinations for different VDD voltages and LCD manufactures. Where did you buy this LCD?

Dave

[midali]

Without the LCD data sheet I don't think I can help ay more. Looking at the controller data sheet does not tell the whole story. There are different interfaces and component combinations for different VDD voltages and LCD manufactures. Where did you buy this LCD?

Dave

You are right Dave !

All LCD's was a gift for me from a friend. He gave me a printed paper with sumary of LCD(7pins):
- Display Type : TM202SIFSUGWA
- LCD OPERATING VOLTAGE : 4.8V
- VDD : 5V
- DRIVE METHOD : 1/16 DUTY ; 1/5 BIAS
- CONTROLLER : ST7036i
- pinouts, tolerance, etc

Really on boards I found 3 LCDs with different serials, but the boards are same, with the same functions. Actually I work on TM202SGFSGWA-B-1A . On internet I dont find a datasheet for them. I suppose that all LCDs with ST7036 controllers have the same init. The serials depending from manufacturers.

The LCD's are mounted on a working factory boards. I desolder the LCD from motherboard for test...also I make a test on a LCD directly on board ( of course that I cuted the tracks from sda, scl and reset pins for separate of rest components board) because I want to be sure that LCD was not destroied from desoldering. Any code I wrote in pic, I tested with potentiometer divider , with V0 short with Vdd.

I see in datasheet that contrast can be configured from registry(case V0 short with Vdd) or from external resistors divider.

Also I have LCDs with 8 pins but I have not any information about them....I have a information only from a serial printed on back LCD side(TM202TCCWUGWA)...here I suppose that have a 7032 controller, but is no important at this time.

Again thx for your help !

[Demon]

I think the LCDs that googled up for TM202 were Tienma. None of them were TM202T or S. It looks like these are custom made, specs could be anything.

I suggest contacting Tienma and asking for a datasheet.

Robert

[DaveC3]

As an outside chance change your pullup resistors to 4.7K, I have never used 1k. The contrast is set in the initialization of the display. I do not think you can change it on the fly.
And lastly give this a try

'****************************************************************
'*  Name    : UNTITLED.BAS                                      *
'*  Author  : Dave Cutliff                                      *
'*  Notice  : Copyright (c) 2014 Use at your own risk           *
'*          : All Rights Reserved                               *
'*  Date    : 12/29/2014                                        *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*          :                                                   *
'****************************************************************
 #CONFIG
        __CONFIG _CONFIG1, _FCMEN_OFF & _FOSC_INTOSC & _WDTE_OFF & _MCLRE_OFF & _CP_ON & _IESO_OFF & _BOREN_OFF & _PWRTE_OFF
        __CONFIG _CONFIG2, _PLLEN_OFF & _STVREN_OFF & _LVP_OFF
#ENDCONFIG
OSCCON = %01101010   'sets the internal oscillator to 4Mhz
      
TRISA  = %00000000  
TRISC  = %00000000  
ANSELA = %00000000  
ANSELC = %00000000  

OPTION_REG.7 = 0
SCL   VAR PORTC.0
SDA   var PORTC.1
Reset    var PORTC.2     'could tie reset pin to   vdd through 10K resistor


pause 100
HIGH Reset
'OPF1 = 0 
goto StartProgram
'********************************************************************************
'=============Initializing LCD==========
ST7036Init:


 


I2CWRITE PORTC.1, PORTC.0,$78,[$00,$38, $39,$14,$79,$50,$6C,$0C,$01,$06] ' 



Return
'********************************************************************************



startProgram:
gosub  ST7036Init
I2CWRITE PORTC.1, PORTC.0,$78,[$40,$48,$65,$6c,$6c,$6f] ' Hello

IdleLoop:
      ' could blink an led here
goto Idleloop

[Demon]

As an outside chance change your pullup resistors to 4.7K, I have never used 1k. ...

Yup, from the manual:

The I2C clock and data lines should be pulled up to Vcc with a 4.7K

Could this be an issue?

Transfer on the I2C bus can be paused by the receiving device by its holding the clock line low (not supported on 12-bit core PIC MCUs). To enable this the following DEFINE should be added to the program:

DEFINE I2C_HOLD 1

Robert


EDIT: I would try one last thing with Dave's code, add PAUSE 250 before every write to the LCD, just to eliminate that possibility.