[SOLVED] problem on segmented lcd module in PIC16F1939

[Rajesh_ece]

Hi

This is my code for segment lcd module
LCDPS=0x3A;
LCDCON=0x83;
LCDREF=0xC0;
LCDCST=0x07;
LCDSE0=0xFF;
LCDSE1=0X03;
LCDRL=0x50;//0x50;//0x51;/


clearAllSegments();
SEG3_A=1; // comm1
SEG3_D=0; // com2
SEG3_E=0; // com3
SEG3_F=0; // com 4

i'am trying to turn segment A for the 3rd digit but other segments which is connected on same segment pin
which is D,E,F were slightly glow which makes unable to read clearly.

then i adjusted the above code for low power and minimum contrast.
but it does n't helps me...........


here i had attached screen short of scope output from that you can see the com output from was good
but segment output was not as like in datasheet( it was a rar file attached)




Real picture of lCD Problem.

**broken link removed**


please help me to solve this problem



thanks and regards
Rajesh

 

[bluelasers]

Do you have schematics?

My first guess would be the you have your logic inverted for the low side. The COM pins connect to ground. Which means to turn on that segment in COM1/PIN1 you would play a 0 on its pin and a 1 on all the others (COM2/PIN2, COM3/PIN3, COM4/PIN4).

Turning on multiple segments may lead to too much current sinking through the PIC16 pin connected to COM1, COM2, COM3, and COM4. So you will probably need a sink transistor for each of these.

To turn on 3A you would put a 0 on COM1/PIN1 and 1 on PIN7, COM2/PIN2, COM3/PIN3 and COM4/PIN4. (0 on PIN5, PIN6, PIN8-14 to just light 3A)

This display is multiplexed so you will need to scan through PIN1-PIN4 (Only one of them can be 0 at any point), each time you will need to change PIN5-PIN14.

I hope this helps.

 

[Rajesh_ece]

Hi


the problem has solved ,

solutions

1 . check whether the lcd segment pins are pull up or pull down or externally shorted to grounded or vdd

when a pullup is added the lcd bias voltage was boosted for vdd so the internal reference for contrast also varied hence it cant be adjustable.

2. if two or more segments turned on for the single segment to be turned ON , try to turn on other segments one by one whether it has link in connection can be easily identified.

3. you can able to see the last document which asked about the segment clock wave was improper ,this happens by the external pullup



Thanks and Regards

Rajesh