G1226 is black&white dotmatrix LCD with 128x64 pixel resolution. Basicly the same LCD is available via Elfa (G1216 should be equivalent LCD with slightly different pin order). Parallel port adaptor was implemented on "vero" board mostly with surface mount components (size 1206) but it can be implemented with throughole components also. Prototype was proven to be fully working with minimal test SW written for MSDOS. The final target is to write Linux kernel module providing all kind of realtime system information. 5V external voltage is required (5V is easy to steal from floppydisk connector).
Basic functionality of interface adaptor:
LCD Data bits D0-D7 is driven directly by Data port
of parallel port.
Parallel port control outputs are driving most
important LCD control signals. These outputs needs 10kOhm pull-ups.
| LCD input signal | Driven by |
| READ/nWRITE | Tied to ground (no possibility to read anything from LCD!!) |
| nRESET | Tied to VCC |
| CS1 | nLINEFEED |
| CS2 | PDTC144ET digital transistor used to generate inverse signal of nLINEFEED |
| DATA/nINSTRUCTION | nSELECTPRN |
| ENABLE | nSTROBE |
| BACKLIGHT | nINITIALIZE (NPN - PNP transistor pair used. Almost all equivalent transistors are suitable) |
| CONTRAST | Negative bias voltage is derived from MAX232 and contrast can be fine adjusted with resistor R10 |
Shematics available SII G1226 PDTC144ET BC857C BC817 MAX232 test SW: lcd.c font.h
Disclaimer: I believe the adapter is fully working and should not cause any harm for computers nor inviduals. Anyway I can not be held responsible for any damages caused by the device. Adaptor should be built very carefully since its very easy to cause permanent damage for the parallel port by shortcircuiting output pins.