Unkown 7.5" TFT LCD displays - Page 1
Forum section: electronics / beginners

author: JoonasM
author_rank: Newbie
timestamp: December 01, 2018, 01:17:36 pm
content: Hi everyone!I am tinkerer with university education in computer engineering although shame to admit that my electronics knowledge ain't as good as it should, maybe I was not clear what really studying is. However believe I have quite good intuition and now I got the will and desire to perfect electronics skills. I bought the bible(Art of electronics)!I am not usually asking help from forums but as I am big fan of Dave and I got myself a project that is said to be impossible I thought this is the place!Ok lets get to the stuff! I salvaged two TFT LCD units with resistive touch panels (FK2-0259 by Arima Display Japan, FH6-0806 by Matsushita Electronic Inc) from two Canon office "printer" display and button module (as you may have seen those grayish panel modules on those printers). I got them separate from the printer so I don't know exactly the printer model, however the display and buttons board was connected to some kind of controller/communication board based on which the model should be IR2200 or similar.The display units come with driverboard with probably unkown chinese driver chip BU16503-07. No proper datasheet available by googleingAfter some digging I got the pinout for the display 20pin ribbon connector from chinese forum(google translate). Although it was not exactly the same display it had the same size and driver chip and also 20 pin pinout. Next I checked if the pinout is correct by investigating the power connections on the communication/controller board that the display was wired to with ribbon. Power rails matched and by the datapins grouping I believe data pins also match.So my first hope was to power up this communication board and hope it also controls the display so I could get some image or most importantly initialization sequence. So I figured out the power rails checked the spec for the mcu(MB89636) thats on this communication board to make sure the supply voltage ->5V.(Display units had backlight power supply modules with which I was also able to light up the backlight from 5V) But no luck. Next I guessed that as there is probably next controller which does the real job, the communication board is probably at sleep mode. So I checked out the interrupt pins, measured the state and as it was high I tinkered that lets try to jump those low (one by one, all at once, pulsing on/off) (maybe it was stupid to believe it works that way). Still nothing happened and by a unfortunate handshake I also jumped interrupt pins that were tied together ( as it seemed odd I didn't plan to short those to GND) and the magic smoke came out. Later if I removed the mcu I found out that those were tied to Vcc beneth the chip. Luckily I have the second communication board also however it seems to be other revision as the placement of components is little different.So I gave up the hope of that kind of simple solution and now I had board that I could use to hardwire the display connections by chasing out better points where to solder wires. The data and control lines went to 74HCT244 buffers through some 300 ohmish resistors, which were decent enough spots to solder wires. By chasing the buffer inputs I found out that I had no chance to get something to the display as the inputs went to some kind of dozen pin main connector. By googleing I found that there are some small TFT display modules(Adafruit) for Arduino also using 8 data lines and just to play around with the wires I soldered to get the display connections I connected the wires to Arduino and run the Adafruit graphic test. I did not expect getting image but at least some flicker of the display which I did get.Ok but to get more serious I have next problem to conquer: the control lines of the display (ref pinout image) are named very strangely and I am not able to figure out what functionality each control pin has. So the reason I post is that maybe some of you experienced guys have met this kind of labeling and knows it straight off (being optimistic here)?The chinese forum gave me some hope as someone mentioned that the initialization should be more or less same to other similar drivers. So if anyone knows any similar 8 bit parallel(I believe) driver chip names/models that have datasheets available (I'll attach more images in the end of the post, so the package could be seen). Then I could dig through some datasheets and even if it doesn't work out at least I learn something new.PS sorry if my text seems odd, I am not natural English speakerhttps://www.upload.ee/image/9252862/lcd1.jpghttps://www.upload.ee/image/9252869/lcd2.jpghttps://www.upload.ee/image/9252882/lcd3.jpghttps://www.upload.ee/image/9252892/lcd4.jpghttps://www.upload.ee/image/9252897/lcd5.jpghttps://www.upload.ee/image/9252900/lcd6.jpg

author: cdev
author_rank: Super Contributor
timestamp: December 01, 2018, 03:36:57 pm
content: Your English is fine as far as readability/understandability for me.

author: amyk
author_rank: Super Contributor
timestamp: December 01, 2018, 06:15:09 pm
content: - BU16503 is a gate array and made by Rohm, which is Japanese, not Chinese. (See attached.)- That's a "controllerless" LCD.FRM (misspelled FEM in your diagram) - frame clockCP - clock pulseLOAD - data latchDISP - display controlVCON - contrastD7-D0 dataGoogling those signal names will show you similar if not identical models that give an idea of what the signal timing looks like:https://pdf-datasheet-datasheet.netdna-ssl.com/pdf-down/K/C/G/KCG047QV1AA-A21-Kyocera.pdf

author: JoonasM
author_rank: Newbie
timestamp: December 01, 2018, 08:09:17 pm
content: Thanks! Now I have something to work on again. I'll keep you updated of the progress.