gnupic: Thread: Re: [gnupic] Connecting an LCD Display to RS232 Interface

On Thu, 6 Apr 2006, Deadly Earnest wrote:

> The place where I work was throwing out some old stuff and I grabbed an 
> LCD Display which is connected via a ribbon cable to a smaller PCB. Now 
> the smaller PCB has a surface mount PIC 16C62A on it and three wires 
> coming off it. I'm assuming that the three wires are a serial interface 
> to the LCD, and the PIC does the work of converting to parallel for the 
> ribbon cable. To test this theory out I was thinking of connecting up 
> the three wires to the serial port of a PC and connecting minicom to it 
> and seeing if I can get anything out of it.

an excellent way to collect parts. :-)

It's likely a 5-volt port; connecting it to the PC serial port is likely 
to damage it because the PC's port "should" (or at least could) be putting 
out as much as +/- 15 volts.  A level converter chip is needed.  A popular 
choice is the old Maxim max232 series, but TI and Linear and probably 
other companies also make similar-functioning parts.

> I was hoping if I could work out how the LCD unit works to incorporate 
> it into a project. There's no markings on the unit that get me anything 
> on the internet. I was hoping that I'd get details on it however it 
> looks like I'll just have to probe it.

If the whole system you grabbed still operates, it would be possible to 
connect a level converter chip from one of the data wires of that serial 
interface to the RX wire on your PC's serial port.  Then you could snoop 
on the data being sent between the onboard PIC and the LCD and maybe learn 
something about the protocol they use.

good luck!

Greg

Greg Hill wrote:
> On Thu, 6 Apr 2006, Deadly Earnest wrote:
> 
>> The place where I work was throwing out some old stuff and I grabbed 
>> an LCD Display which is connected via a ribbon cable to a smaller PCB. 
>> Now the smaller PCB has a surface mount PIC 16C62A on it and three 
>> wires coming off it. I'm assuming that the three wires are a serial 
>> interface to the LCD, and the PIC does the work of converting to 
>> parallel for the ribbon cable. To test this theory out I was thinking 
>> of connecting up the three wires to the serial port of a PC and 
>> connecting minicom to it and seeing if I can get anything out of it.
> 
> 
> an excellent way to collect parts. :-)
> 
> It's likely a 5-volt port; connecting it to the PC serial port is likely 
> to damage it because the PC's port "should" (or at least could) be 
> putting out as much as +/- 15 volts.  A level converter chip is needed.  
> A popular choice is the old Maxim max232 series, but TI and Linear and 
> probably other companies also make similar-functioning parts.

It could also be a serial interface to another micro, and in that case 
it could be SPI.

Cheers,
Marco

-- 
Marco Pantaleoni

elastiC language developer
http://www.elasticworld.org

On Fri, 7 Apr 2006, Marco Pantaleoni wrote:

> It could also be a serial interface to another micro, and in that case 
> it could be SPI.

a very good point.  Could be I2C as well.  Maybe the original poster can 
find an oscilloscope in order to analyze the signals on those wires 
(again, assuming that the original device still functions!) to figure out 
the protocol used on those lines.

Greg

>> It could also be a serial interface to another micro, and in that case
>> it could be SPI.
>
>a very good point.  Could be I2C as well.  Maybe the original poster can
>find an oscilloscope in order to analyze the signals on those wires
>(again, assuming that the original device still functions!) to figure out
>the protocol used on those lines.




Original poster here people. I'm sorry this stuff has only come to light as
the company is moving premisis. The device is an embedded device and
everybody who worked on it has left and I can't find any documentation on
it.

Basically I'll try and see if it's a serial link and if not then I might be
able to look into SPI and I2C. I never even thought of those. what ever it
is there's a PIC processor on the other side of the three wires so if the
worst comes to the worst I might be able to suck the code out of it and have
a look at it. Actually that might be the easiest option. The chip is a
PIC16C62A surface mount.

I'll let you know how I get on. I just found one in good order and managed
to get it powered up. Sweet. I've got nearly 20 16x4 character LCDs to play
with. I'll have LCD's on everything by the time I finish if I work out the
protocol. I've no silly scope and I'm only starting so I'm not going to buy
one just yet. I'll try find out if I can get my hands on one.

Don't come back and tell me that by salvaging these I'm saving myself a few
pence I don't want to know ;-)

thanks for all your advice

John Whitmore

PS just getting into this and picked up the picclite compiler. I'd like to
use linux tools as much as possible but went of half cocked and got a
Vellman K8048 PIC Programmer so I'm on the windows for that. Oh well next
time

Deadly Earnest wrote:

> Original poster here people. I'm sorry this stuff has only come to light as
> the company is moving premisis. The device is an embedded device and
> everybody who worked on it has left and I can't find any documentation on
> it.
> 
> Basically I'll try and see if it's a serial link and if not then I might be
> able to look into SPI and I2C. I never even thought of those. what ever it
> is there's a PIC processor on the other side of the three wires so if the
> worst comes to the worst I might be able to suck the code out of it and have
> a look at it. Actually that might be the easiest option. The chip is a
> PIC16C62A surface mount.

Perhaps you could infer what protocol is used by looking at which pins 
of the PIC the three wires are tied.

Cheers,
Marco

-- 
Marco Pantaleoni

elastiC language developer
http://www.elasticworld.org