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Topic: Unknown LCD - Longshot (Read 569 times) previous topic - next topic

miker

I found an unknown LCD in the local elec. surplus store and have been challenged to make it work.
It is a 2 x 16  display (5x7 block).  It has a serial interface (no manufacture ID although a Bing
search on an assy # on the board points to a url for "IndustrialElectricDirect" but the url registration
has expired.  There is an 8 pos screw terminal connector with the following lables:
[font=Courier New]
1   2   3    4   5    6   7   8
+ | - | - | RX | - | TX | + | -
[/font]
There is a 7805 regulator on the board so I applied +9V to pins 7 and 8.  This causes a underbar
cursor to be displayed in pos 0 (row 1, col 1).  I've found that pins 3, 5 and 8 are all common grounds.
Pins 1 and 2 are isolated (pin 2 is not connected to pins 3, 5 or 8 ).  Pin 1 is not connected to
the +5V regulator output.   I've connected pin 4 (RX) to my Arduino UNO pin 1 (tx) and pump
an ascii letter 'A' to it and cycle thru baud rates from 1200 to 38400... but the cursor never moves nor
does the letter 'A' appear.   

Its a longshot that someone might recognize the LCD based on the 8-pin screw terminal connector
configuration..??

tack

Making a guess that pin 1 and 2 might be a backlight connection?

A picture of the thing would be very useful ;-)

miker

I've attached a picture with a few notations.  I've discovered that ALL of the terminals
marked as "-" are common as are the "+" terminals (although the appearance that
the "+" terminals may be common could be the result of some back circuits.....). 
I tend to aggree the first "+" terminal is probably a backlight and the "+" terminal
adjacent to the "TX" terminal is supply. The 8-pos switch probably sets the buaud rate
and other configurations but I've tried setting it to various random positions with no
observable change. 

floresta

#3
Jan 25, 2013, 03:17 pm Last Edit: Jan 25, 2013, 03:26 pm by floresta Reason: 1
Quote
I've connected pin 4 (RX) to my Arduino UNO pin 1 (tx) and pump
an ascii letter 'A' to it and cycle thru baud rates from 1200 to 38400... but the cursor never moves nor
does the letter 'A' appear.    

I don't think you will get very far with this approach for a few reasons.  Here's why.

The SP232ECT converts RS232 signals to TTL signals.  This means that the RX and TX lines are expecting RS232 level signals, +3 to +15V for a logical '0' and -3V to -15V for a logical '1'.

The KS0066F is the actual LCD Controller which contains all of the memory and also drives the 16 characters on the left hand side of your display.  The HD44100H is an Auxiliary Controller which is used to drive the 16 characters on the right hand side of your display.  

The LCD controller chip is expecting 2 or 3 control signals and 4 or 8 data signals at it's input which leaves the K0V498 as the interface between the serial signals from the RS232 transceiver and parallel signals that the LCD controller is expecting.  Most likely it is some sort of microcontroller with all those pins.  The red DIP switch could be setting the baud rate that this device is expecting.


Quote
This causes a underbar cursor to be displayed in pos 0 (row 1, col 1).

This part is good news.  It means that your LCD is powered and is being properly initialized.

You will have to come up with some way to generate true RS232 voltage levels to send to this device.  If you have an ancient computer with a serial port, or a USB to RS232 adapter for a newer computer, you could use a terminal program such as Hyperterminal and tinker with various baud rates and protocols.


Don

miker

Thanks all... good pointers...   
XD

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