Description

<style>.e_editor{font:14px/24px Arial,'microsoft yahei','Times New Roman','b8bf53';}.e_editor div,e_editor p,e_editor td,e_editor th,e_editor li{font-weight:inherit;font-size:inherit;font-style:inherit;font-family:inherit;}.e_editor ul{margin:-10px 0 20px;}.e_editor li{padding:5px 0;}.e_table{width:96%;border-collapse:collapse;empty-cells:show;}.e_table th,.e_table td{padding:5px;border:2px solid #eee;}.e_img{padding:10px 0;text-align:center;}.e_p{line-height:20px;padding:0 0 20px;text-indent:0em;}</style><p><span style="font-family:inherit;font-size:inherit;font-style:inherit;font-weight:inherit;text-indent:0em;">Remaking the PDP-8/I using the Pi, simh &amp; a replica front panel: a true catching project!</span></p><p> Goal: a (very) low cost full replica of the PDP-8/I. </p><p> Design: use the $20 Raspberry PI Model A+, a custom front panel PCB to mount it behind, and 26 nice-to-use toggle switches. Extend the simh emulator to drive the front panel. </p><p> Reason: PDP-8 replicas can get very expensive very quickly. The idea was to do the exact opposite: design a faithful replica using minimum parts. Made possible by the fact that the computing engine is available for $20 (Pi model A+) and in software, there’s no better replica of PDP-8 functionality than the simh emulator. </p><p> Result: Pi drives the 92 leds and 26 switches using a multiplexing process running in parallel to the simh emulator. Only a few ARM instructions are necessary to update the front panel during a PDP instruction cycle. An acrylic front panel faithfully reproduces that of the original. </p><p> Components </p><ul class=" list-paddingleft-2"><li><p> 1×Raspberry Pi (Plus or 2)needs 40 pin GPIO connector </p></li><li><p> 26×Toggle switches </p></li><li><p> 12×390 Ohm resistors </p></li><li><p> 26×4148 Diodes </p></li><li><p> 1×UDN2981A (optional)Interface and IO ICs / Peripheral Drivers and Actuators </p></li><li><p> 1×PCBDesigned in Kicad/Open source hardware design </p></li><li><p> 89×LEDs (5mm, High Brightness)Electronic Components / Misc. Electronic Components </p></li><li><p> 3×1K Ohm Resistors </p></li><li><p> 1×2*20 pin header for mounting the Raspberyr Pi </p></li></ul>