I took apart an MS-CR1001 alarm clock, which has a little projector to put the time on the ceiling. Here's a picture of it in action, and a picture of the circuit for the projector with the LCD/lens removed:
I was wondering if it'd be terribly difficult to interface with the LCD driver through the five wires using an Arduino to make it output custom data.
I did find the datasheet for the ET6621 driver. Unfortunately, I do not speak Chinese. I ran it through a translator, but it didn't clear it up very much. And I'm not sure I'd be able to figure out how to use it even if it was in English.
Any tips on how I might be able to learn to use this thing?
If you are going to interface that boards to something, you need to know what the various signals are that applied to each connection. They can't all be DC! So both the voltages powering the board and the control signals will have to be duplicated. Do you have an oscilloscope to see the signals?
Ah ok, I do not have an oscilloscope, just a multimeter. The closest thing I have experience with is a 595 shift register, and I was hoping it was a similar mechanism.
How would you know, if you don't have a scope? But if you are going to attempt to use unknown devices, you need to get an oscilloscope and perhaps a logic analyzer. Then you can document your boards and then begin to develop the hardware and software interfaces.
I wouldn't know, I just thought there might be some LCD driver "standard" that would apply to this chip. I'm just getting started with this kind of stuff. Maybe in the future I'll get an oscilloscope and come back to this thing.
Read the data sheet specs. It's a display driver for an LCD. Is there another part? The diode on the board doesn't have the ability to scan, but it might be a projection light for a transmissive LCD screen in the nose of the device. There's nothing really magic that makes it a projector from that chip's POV. Its the projection optics that make it unique.
You can get a cheap, ccp, one channel scope for $40 or so that will give you an idea of the signals. But for real analytical work you need dual trace so you can compare timings, but the data sheet mostly explains that. The device is a self contained clock driver for an LCD. It Accepts clocked serial data with data formats explained in the docs (yes, in i-cant-read-Chinese) but electrically a scope ain't going to tell you much.
Voltage levels too are found in the data sheet even if in Chinese, Vdd is an easy to spot spec.
Hmm ok thanks for the insight. You're right, it's just an LCD in front of an LED. This is probably a bit advanced for my current level of understanding, though.
Cool thanks. Now I know the five wires are probably CS, WR, DATA, Voltage, and Ground. Still probably won't know how to figure out the signal format, but I'll keep looking at the translated datasheet.
I'm going to just try powering it the same way as a shift register, since it seems like it uses a lot of the same terminology (clock, latch, data), and I'll see if any of the LCD segments change.
I just did a continuity check and yep, the five wires go to those five pins. I'll try running a shift register program on it at some point. I guess it needs 32 bits of data since there are 32 output pins? The datasheet does say it's a 32x4 display matrix. I'm not really sure what that means, or if I need to worry about the x4.
So that would make the data stream ASCII or kanji. Send 0x30-0x39 and 0x41-0x46 to it. The 0-9 should show no matter what language, A-F or random ideograms will appear depending on ASCII or kanji. Or not.
Look at the data sheet. There are bits labelled Axx and Dxx. Axx is the character location and the Dxx is the ASCII/kanji value. Just a (well) educated guess. The Axx lines will be 5 bits for col (0-31), two bits for row (0-3) for 7 bits total. There should be 8/16/32 or whatever data bits. Count the pulses in the timing diagram over a Dxx labelled trace.
Ok, I think this is the timing diagram I need. The translated title of the diagram is "Write Mode (Continuous Address Write)". I count 6 A's and 17 D's.
The labels at the bottom say "Memory address 1", "Data 1", "Data 2", "Data 3", " Data 4".
