Like many Hackaday readers, [Steven Stallion] Have set their sights on the copy of PDP-11 [Oscar Vermeulen] For some time, this summer he finally had the opportunity to build one of his own. However, although most owners may only be content to watch a Raspberry Pi-based retro-style computer flash by on the shelf, he wants to explore the use of the machine for more practical purposes. The end result is the PiDP-11 I/O expander, An add-on that allows modern minicomputers to interact with the world around them.
Develop after some discussions [Oscar] Own, the expansion board based on Microchip MCP23016 is neatly installed on the PiDP-11 PCB, and [Steven] Make sure that his installation guide is in good agreement with the copy of the document. The Pi’s I2C bus is actually disconnected on the original PCB, so you only need to solder a connector and connect some jumpers to the place where the expander is installed. You also need to pull 5 V, and the installation guide has some tips about convenient connection points.
Each expansion board provides you with 16 GPIO pins that can be accessed via I2C, including support for interrupts that are connected to GPIO 19 on the Raspberry Pi. [Steven] Note that if you need more free pins, you should be able to stack multiple expanders, although you may need to fiddle with pull-up resistors and I2C addresses.
The expander’s PCB has been released under the BSD two-term license, so you can create your own copy as you see fit. But if you want to save some time, [Steven] Provide assembly boards on Tindie.
since [Oscar] We made fun of it at the 2015 Hackaday Supercon for the first time, and we have been fascinated by his excellent PDP-11 replica. We are always happy to see someone pick up one of these great kits, especially when they come up with a way to extend it in unexpected ways.