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Topic: Graphical LCD (ST7920 Driver) - a warning and a question (Read 7212 times) previous topic - next topic

Joshb60796

I'm working with the same or similar LCD (12864B ver2.0). I've included an image of the back of it. I have no yet connected this LCD to anything as I'm still trying to learn how to wire it to the UNO without destroying anything. I've read through this forum post to try to give as much info, so helping me would be easier. I get a resistance reading of 33.7 ohm between BLA&A and 0.6 ohms between BLK&K   I see at JP2 there are three pads, two are labeled S and P and the middle pad is not labeled and is connected to the PSB edge connection. Do I solder a bridge between the S pad and the middle pad to put it into serial mode?  I'm connecting to an authentic Arduino UNO. I am a beginner. I greatly appreciate any info anyone can add.

dc42

#16
May 15, 2014, 10:05 am Last Edit: May 15, 2014, 10:08 am by dc42 Reason: 1
So your LCD already includes a series resistor for the backlight (the 33 ohms that you measured). It also has the contrast adjustment pot built-in. You are probably right about JP2, you can either solder a jumper there or you can connect the PSB pin on the edge connector to +5V or ground to select serial or parallel mode. But I suggest you trace that wire from the jumper middle pad to the PSB pin on the edge connector, to make sure that it isn't already connected to +5V or ground through a 0 ohm resistor, as was reported by someone else using a similar GLCD recently.

EDIT: I can't see any 0 ohm resistors in that photo, so I think you are safe.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

Joshb60796

I'm wired up and I soldered the middle pad to the s pad and loaded one of the example scripts into my UNO and everything works perfectly the first time!! I'm totally siked! Has anyone here ever used the u8g library with this screen? I only had one semester of C++ and I'm finding it very hard to follow. I was hoping it would be closer to how I was using the lcd print command. I'm building a coffee roaster and I just want to output data to this nice large screen, like temperature, time, fan speed, and deviation from my PID profile instantly and over the last 5 or 10 seconds. Does anyone know of a better library maybe? I don't really need graphics like frames and such. I've already put about 10 pounds through this roaster and now I want to jazz it up a bit.

dc42

I know of only two Arduino libraries for ST7920-based displays. The first is the u8glib library that you are currently using. The second is a library that I wrote for a particular application. You can find it find at https://github.com/dc42/arduino/tree/master/Libraries/Lcd7920 along with a simple sketch that uses it. It's less comprehensive than u8glib, and it uses up 1K of memory as an image buffer. I don't know whether you would find it any easier to use than u8glib.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

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