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MOP-AL404C backlight question
Posted: Fri Oct 03, 2008 7:21 pm
I find the documentation is pretty sparse for this display. I had the Backlight wired to +5 and Gnd on Pins 17 and 18. My voltage regulator was heating up very quickly.
Disconnecting the Backlight solved that problem. What do I need to do to get the backlight working?
All suggestions welcome
Posted: Mon Oct 06, 2008 9:38 am
I understand you're having a little trouble finding information regarding that MOP-AL404C display. Unfortunately, you've chosen the parallel unit, so you'll have to do a little bit of work on your own to get it going, but we'll be here to help as much as possible.
As specified in the electrical characteristics section of the manual
, you'll want somewhere between 3.8 and 4.3 volts supplying the back light at about 500mA. Make sure you have a resistor inline when powering that back light, and keep and eye on the current. You may have to play around a bit to find the optimal value, so a potentiometer may be a good idea. Ultimately, I'd expect a value somewhere in the single to double digits for that resistance.
If you do have any other trouble with that unit, please just post your findings and I'll do my best to point you in the right direction.
Posted: Mon Oct 06, 2008 11:42 am
Thanks for the information. When you say double digits, should I be assuming something in the 10K to 20K range?
I appreciate your offer of assistance. I do have another post in this forum with my progress and the notation that I am not getting characters. I suspect it is a user error - me.
I downloaded a copy of the manual for the driver chip itself which filled in a number of blanks. I also found a manual for the raw displays (sorry I am at work and don't remember the manufacturer). They have a good manual as well.
I didn't realize that I was ordering such a large display, but I think it will work out fine.
I am curious if I can reference the pixels without having to create custom characters. The picture associated with this display on your site shows a bar graph
http://www.matrixorbital.com/index.php? ... acter-lcds
I would like to set up my display this way ideally with 4 digits (full 4 line height) on the left and 4 text lines on the right. I chose the display because of that picture.
So far I have not found any documentation that would help me figure that out.
One step at a time. If you folks can help me sort out getting text displaying I might well be able to figure out the rest.
Posted: Mon Oct 06, 2008 3:53 pm
No worries, good to see you've been able to pull a little more info on that unit.
For the back light I was actually talking the 0-100 ohm range; I think we've got about 2 ohms total resistance on our board. Just a small value is needed to regulate the voltage to make sure the LED back light doesn't gobble it all up.
Unfortunately, there is not way to reference individual pixels, you'll have to use those eight customer characters. The graph in the image is just custom characters of varying heights, so it should be relatively easy to recreate.
As for the digits, those will be the same idea; just custom block characters to create larger digits. We are able to save different banks of customer characters using our daughter board, then use one set at a time. To do graphs and larger text you'll have to do something similar.
That should about cover the topics here, I'll ask for your patience on the other post as it's my colleague's first day back after a few months away and she's still getting caught up. I'm sure she'll have a look as soon as she's got a little time, and let you know if anything jumps out.
Posted: Mon Oct 06, 2008 4:19 pm
Thanks for the info on the resistor. I will add that in and bring my backlight back on line.
From the manual it looks like I can only create 8 5x8 characters. I would love to create large digits from 0 to 9 that would span all 4 lines. Can I write to the space between lines or is it inaccessable?
I could save the patterns in an EEPROM easily enough. Can I call and external EEPROM and write that information to the display? or does it have to be contained in the display memory?
Posted: Tue Oct 14, 2008 2:42 pm
No worries, hopefully the resistor change does the trick.
You are correct, you can only create eight of those 5x8 characters, and no, unfortunately, the space in between cannot be used as it is not active. You can definitely save what ever you need to an EEPROM, and bring the characters up from there. For the larger characters, you'll have to create 5x8 shapes, then organize them correctly on the screen to make digits.
It's definitely doable, we've got that option on our intelligent displays, so if you have any trouble just let me know.
Posted: Tue Oct 14, 2008 4:36 pm
Lets drop this thread and stick with the AL202 since I have temporarily shelved the 404C
It is entirely possible that there is enough space available for me on the AL202 to do what I would like. I did read something about reserving bank 0 for the splash screen. If I don't want a splash screen, can I use that the same way I would use banks 1 - 3?
Posted: Wed Oct 15, 2008 11:12 am
Will do, just put any comments over on the 202 and I'll get to them there. Basically, you can do what you like with all four banks. However, each holds characters that you may find useful.
Bank 0 is stated as being for start up as it contains custom characters and will be initialized by default. You can change the characters in it, and any of the other banks as you like. Note that the others will have special characters for larger numbers and graphs already saved, so if you want to use those functions I'd suggest keeping them as is.
Anyway, if you do have any further questions, just throw them up on the 202 thread for now and I'll get to them there.