![]() BLK: Backlight cathode, connected to GND.BLA: Backlight, connected to +12 V via R=270Ohm.VOUT: A reference voltage but not used in my project.RST: The reset pin, must be pulled to GND for 1 ms or so and then set to high to reset the module when program starts. ![]() PSB (set “low” if you project serial communication or “high” if you project parallel communication (4- or 8 bit bus width possible)).E (the “enabled” pin that goes high when a byte of data is transferred).RW (“low” when writing data, “high” when reading data from the module).RS (determining if there is data (pin to VDD i.VO (a contrast set but without function with my module).The LCD12864 is wired to the rest of the circuit by a 20-pin header strip in 2.54mm (0.1″) spacing. The LCD module communicates via 8- or 4-bit parallel mode or a serial “SPI” derivate. But there is also the possibility to drive them in full graphics mode with your own fonts to be used. The modules have built-in ROM-based standard character sets like they are familiar from the well-known line oriented modules like the 16×2 ones. The screen is 128 pixels wide and 64 pixels high. Hardware: These LCD modules have 2 controllers of the ST7920-type inside. I will only refer to the things that I think are not clear in the data sheets or are controversial between the various versions of the papers. ![]() Read them before you start! At least once and by skimming. The problem is: You can get ones that don’t cover even the minimum you must know to get the thing working. What to do first: RTFM! Data sheets for this module are widely available and I strongly recommend reading one of them. You will find this source code by the end of this paper. So I decided to write my own code (mainly as an academic exercise □ ) in standard C language for the AVR controller family. Unfortunately I did not find any “non-Arduino” modules on the web to meet my requirements. ![]() For this project I bought one of those larger graphic display modules that are sold from incountable Chinese vendors: LCD-12864-ST7920 I am currently planning a new all band transceiver that might be a little larger than the “Microtransceivers” I built this year. ![]()
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