Here is the last improvements in Arduino code, and my prototype finally has 2 Arduino boards and drivers to drive two pairs of 24V DC system garlands . There is now 11 programs to aminate lights.  

HPDisk was originally written almost 10 years ago as a means to store and load configurations for (hp) measuring instruments. Over the years the project has gotten a life of its own and people have been using it for all sorts on equipment, including old HP computers. HPDisk ran fine with the HP85, at least as long as you had the disk ROM installed, but when someone had problems getting it to run with the HP9816, I was stumped. No amount of log and trace files helped me to solve the problem so in the end, out of curiosity, I managed to lay my hands on a HP9816 on ebay. It was in working order but very dirty and the keyboard was flaky. In addition the fan was broken. After extensive cleaning (have never seen so many dead spiders inside a computer before) I was able to start testing it with HPDisk. It quickly turned out that my selection of pullups, 10k to lessen the load on the bus, did not play well with the 9816. Put another GPIB unit on the bus and we could signal. So I lowered the pullups to 3k3 (they should really be 3k1, but 3k3 is close enough). Second hurdle was timing. The 9816 was too fast for my polled design. There is a newer, faster and more flexible processor, the 18F46K40 that is pin-compatible with the old. In addition does it have its own oscillator which means less components and two extra I/Os.  I decided to use that one, giving existing customers an upgrade path. Replace the processor on HPDisk and program the new firmware. The GPIB-receive was completely rewritten. It is now interrupt-driven and can buffer up to 512 bytes of data whilst the processor is busy decoding. I also did some tweaks to the Amigo and SS/80 routines. This FW plays nicely with the 9816, so it should work well with any of the members of the HP200-series. You can save and store programs or even boot BASIC from HPDisk MKII. Out of curiosity I then ported back the code to the 18F4620. The only real changes apart from some registers and fuses being different is the GPIB ISR. I was able to make it work on the 4620 as well, but sadly not fast enough for the HP 9816

Have posted the beta of the MKII FW. This FW has been tested with the HP9816, HP35665A, HP1631D, HP3852A

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Nope. You need to flash the new firmware. Actually. I have not tried, but see no reason why one would do so. The new FW has some exiting features: Support for the HP98x6 series of computers Disk 0 can select between 16 different image files Disk 1..3 are fixed image file names All filenames configurable in hpdisk.cfg. No need to call them "lifdisk2.bin" etc Disk activity LED Support for a DS 2417 RTC connected to the aux port and provision to read and write that as a file. The new FW is currently in beta, but it works just fine with the original PCB