Interfacing with HP-HIL
cmhanson at eschatologist.net
Sat Apr 30 21:22:41 CDT 2016
Has anyone used any modern hardware to interface with HP-HIL gear? (HIL is Human Interface Link, not to be confused with HP-IL.) I’d like to interface an HP 46085A Control Dial Box <http://www.hpmuseum.net/display_item.php?hw=684> with my Mac via USB.
But before I go any further in this—I’ve already put a bunch of effort into trying to get it to work—I realized I should probably ask here to see if anyone else has done it. Has anyone?
HP-HIL uses what *should* be a pretty basic serial protocol with available docs. (Thanks, Bitsavers!) The only odd things about it are (1) a data rate of 100Kbps (rather than say 115Kbps) and (2) the use of 12/O/1 framing (rather than say two 8/E/1 frames per packet and (3) a 12V supply line for what’s otherwise a TTL-compatible bus.
Getting the actual host interface IC is just about impossible without removing it from existing equipment, and the client interface IC doesn’t really seem like it would act as a host. The weird framing means virtually no common UART will work, and the data rate means something like an Arduino only has 160 cycles/bit to work with.
It looks like I might be looking at either using either an Arduino or a CPLD to implement a 12/O/1 UART to talk to the control dial box, and using a second Arduino to communicate with that (via a parallel interface) to actually implement the USB HID via the builtin HID stack functionality on some models of Arduino.
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