LCD 122x32 with SED1520

Hi.

I am trying to connect this SED1520 122x32 display to an Arduino Nano but without much luck so far.

Datasheet: https://dl.dropboxusercontent.com/u/5062915/Duino/LCD_122x32.pdf

I have connected according to datasheet and glcd-v3 manual, except that the display have no R/W pin. The datasheet shows a R/W pin in the timing characteristics and in command list so I am a little confused here.

All I got when running GLCDDemo is a little flickering when the program runs.

I no longer maintain the glcd library but have created a newer library openGLCD. It can be found here: https://bitbucket.org/bperrybap/openglcd/wiki/Home It is licensed GPLv3. It is a superset of the glcd library with bug fixes, and many new features. If interested, read the wiki and then the html documentation.

You need to see if you can find a better data sheet to help clarify the pins. As is common in these datasheets, this data sheet has errors in it. The pinout on pages 4 and 8 don't agree, and both are wrong. There must be at least a r/w pin for 68 series mode and both read and write pins for 80 series mode.

Did the vendor give you this datasheet? You might try googling for the part number on the back of the board.

Getting the correct pinout information is critical as hooking up wires incorrectly can potentially damage the glcd or the Arduino.

If you can find a better datasheet I can help you get it up and running on openGLCD.

--- bill

Hi.

Thanks, I will look at the new library.

Here is the display:

The table in page 8 is true, pin 11 and 18 is NC. When looking at the back of the PCB the chip is marked (GND)78 - the R/W pin on the chip is pin 77, but the pin left of pin 78 is pin 76 = E, so R/W must be grounded and the module is write only.

...and I found this, wich also say "write only": http://www.eeweb.com/blog/circuit_projects/graphics-lcd-interfaced-with-atmel-avr

In terms of that referenced library mentioning “write only”.
A library can choose to use a frame buffer and never read data from the display.
That doesn’t necessarily mean that the module is write only.
For example, the u8glib library operates in “write only” mode
but it still does reads when interfacing to displays like ks0108 and sed1520 to check for ready status.

openGLCD has a read cache mode where it will never read data from the display,
however, it will still read the status from the display to be able to tell when
it can send data & commands to the display.


Are you saying that traces just to the left of each of the labeled fat
ground pin 78 traces are the E signals and go to glcd module pins 6 an 7?

Can you show a photo of the other side of the board?

On the other side are there no traces running to glcd module pins 11 and 18?

If so, there doesn’t seem to be enough pins.
With motorola mode (68 series) you need a r/w pin and a strobe.
With intel mode (80 series) you need a read strobe and a write strobe.

Motorola mode could work if the r/w pin was grounded but then
you could never read the status register to know when commands
have completed.

There would be no way to run Intel mode since the write stobe pin
is stuck grounded.

It seems very odd that the module would leave two pins (11 & 18) not connected
to anything and hard wire the r/w(WR) pin to ground.

If the module has the r/w(WR) pin hardwired to ground,
openGLCD will not work with the module “as is” since the library
wants to read the status register to know when the module is ready
to receive data/commands.
Without this, the code would have to be changed to use blind delays instead
which requires code changes.
Also, I have no idea how long those delays need to be.

Hmmm... I put this display back in the display-drawer for now - I have some larger SED1520 display that HAVE a R/W pin :D

Thanks for helping so far.

Depending on the modules you may need some of the openGLCD code updates that I just recently added
but are not in the latest published release.

Some 1520 based modules like the mtb368 use 2 chipselects and one enable vs 2 enables like the vk5121

If you have a module like this you will need the newer code.

The code works I just haven’t released it yet as I’m not done with the documentation
updates I also want to include.

– bill

Hi.

Now working with the other display and openGLCD: http://www.edersales.com/eletronic/sed1520/sed1520.php

Some of the sed1520 displays can work ok at room temperature when the Vo signal is left unconnected or connected to ground.

How is your pot wired up? It looks like it only has two wires going to it which won't allow any adjustment. I also only see 1 voltage supply so no negative voltage which the link said was required for the contrast circuit.

I bring all this up because the contrast circuit looks odd in the photo. Do you get any contrast variation when you adjust the pot? Am I missing something?

BTW, that demo is a GLCDv3 demo running openGLCD in GLCDv3 emulation mode.

--- bill

This display is prepared for onboard negative power so I have soldered an ICL7660 on, and now I use a fixed resistor:

Maybe there is some timing adjustment to do - there is no reset line and sometimes I have to power up a second time to get rid of some blur.

When it runs fine, it keeps running fine.

OZ2JP: This display is prepared for onboard negative power so I have soldered an ICL7660 on, and now I use a fixed resistor: Very interesting.

Maybe there is some timing adjustment to do - there is no reset line and sometimes I have to power up a second time to get rid of some blur.

When it runs fine, it keeps running fine.

Can you further describe this "blur" misbehavior? Or capture it in a video? I'm not quite sure what is happening.

Now with a better power source there is no problems, so it must be a weak connection in the breadboard that coursed problems while starting the display.

And now with backlight, wich consumes 160mA :astonished: