Some Questions About Workings of a GLCD - Page 1
Forum section: electronics / general

author: Utku
author_rank: Newbie
timestamp: December 15, 2014, 10:24:35 am
content: Hello,I am trying to use a GLCD for my project. Looking at the module's and its drivers' datasheets, some questions have formed in my mind. The links to datasheets are as follows:Linkfor the datasheet of the GLCD module.Linkfor the datasheet of the GLCD module's segment drivers.Linkfor the datasheet of the GLCD module's com driver.My questions are a bit lengthy but if you could have time to answer them, I would be very very grateful. So if you would excuse, my questions are as follows:1) First of all, why aren't pin numbers of the drivers shown at the block diagram at p.10 of the LCD module's datasheet? Also, not every signal's name is shown as well. Am I supposed to be able to understand how the module works without knowing which signal goes to where in the module?2) In the display module's block diagram (at p.10 of the module's datasheet), CS1 and CS2 are connected to their respective segment drivers. Also, there are 8+5 pins connected to each segment driver from the MPU. On the other hand, in the application circuit given in p.20 of the NT7108C datasheet, all CS1B, CS2B and CS3 signals are connected to all segment drivers. Furthermore, there are 8+7 pins connected to each segment driver from the MPU, instead of 8+5 pins. Now what is the meaning of this? Where are the remaining 2 pins connected from in the display module's diagram? Also, why aren't CS1 and CS2 connected to both segment drivers in module's diagram, unlike the application circuit given in p.20 of NT7108C?3) In the p.6 of the datasheet of NT7108C, pins; CS1B, CS2B and CS3 are defined as follows:"Chip selectionIn order to interface data for input or output, the terminals have to be CS1B=L, CS2B=L, and CS3=H."and throughout the entire document, only that given combination of CS1B, CS2B and CS3 is mentioned. My question is: If only a single combination is being used, why are there 3 pins provided for a single task, instead of just 1?4) Another point is, I couldn't figure out how am I supposed to connect the GLCD module to my MCU, an ATmega32. I heard that conventionally, SPI is used to connect peripherals to an MCU, but thing is, SPI uses serial connection and the GLCD module that I use has a parallel port for data transfer. So I am a bit confused here also.5) My last question is, I came across a tutorial onthispage about the use of the GLCD. They put an architecture diagram (named: "GLCD pages") in the website and it explains the form of the architecture very well. My question is, how were they able to understand that architecture is in that way? If that's by looking at the datasheets, could you please underline the places in the datasheets that helped them coming with that architecture diagram? If the sources were not the datasheets, but the experiments they have performed using the module, then my question is: Are there many cases where datasheets of components does not provide enough information and hence, one needs to understand the architecture by conducting experiments, rather then by thoroughly reading the provided datasheets?I realize that the questions I asked have been lengthy but if you could have time to explain the answers of these questions, I would be really grateful. Thank you very much in advance.Sincerely

author: Wilksey
author_rank: Super Contributor
timestamp: December 15, 2014, 12:00:22 pm
content: FYI, Your datasheet links are broken, with added " characters.1. All relevant pins are shown on P10, apart from backlight as far as I can tell, the pin information is on page 8.2. CS1 and CS2 refer to the chip select of the LCD module, not the individual driver chips, you can common them all together to address all segments at once, the databus and other pins are common between the drivers.3. Ignore the datasheet for the drivers when it comes to connections, the LCD module has this already done for you, know that CS1 is segments 1-64 and CS2 is segments 65-1284. You connect the 8 DB pins (DB0 - DB7) to your microcontroller, you can use a shift register or connect them directly to your MCU, the diagram on P10 lists the conventional connections required, and elsewhere in the documentation will be timings etc used to drive the LCD.5. I cannot get the page to load properly, but 99% of the information you need to know is in the datasheets, the other 1% can be down to experimentation, most of the time manufacturers assume a certain level of understanding about the way things work, some require more than others to fully understand, a lot of them dumb down the application notes and examples for beginners though. The chipset is based on the common KS0108 chipset, which the one in that display is just a "variant" of the chipset, made by another company with their own spin on the name, but essentially the same "guts".

author: amyk
author_rank: Super Contributor
timestamp: December 15, 2014, 03:22:01 pm
content: You only really worry about common/segment drivers individually if you're driving an LCD which is "controllerless" or "dumb", i.e. the ones that are basically a shift register/level converter. Otherwise you only have to interface with the controller, which will handle the timing of the signals to drive the crystal/glass itself.