HP 75 and the PIL-Box

[Oulan]

Yes the latency is the main problem.

For HP-IL, the latency of the medium kill speed. I started to make some experiment on go71b for hp-il over wifi (with patched virtual il programs on a pc), but as the message should travel the whole loop before sending the next, I got a throughput of 5 bytes/sec !!

Actually I got some nice usb-serial adapter from FTDI and even usb-usb null modem adapter (it is seen as a serial device at each end with very hight speed).

One day I will try some experiments on go71b to look further in implementing HP-IL protocol but only on usb-usb or usb-serial medium as they support android with complete drivers.

Perhaps an idea to increase the throughput of the sender is to 'fake' the reply from the loop. If you know exactly what devices are on the loop, you can 'forge' the message after its travel on the loop as soon as you send it (if you make the assumption that all devices are ok and work well). But if you pull off the device ....

It can be done with go71b (you can change the behavior of the hp-il stack) or from emu71. This can also be done if the controller is connected directly to a usb/serial virtual il device (you can forge the reply). For PIL-Box, this is quite complicated as you need to rewrite a large part of the driver.

For pil-box, you can use this idea: make a special usb device which isolate the 'virtual loop' from the pil-box. This device forge immediately the reply message and then manage the virtual loop itself. No change are needed on the PIL-Box, but it can be quite hard to do for the device code.

This can be done for 'virtual loops' but for 'real loops' I don't have any ideas, sorry.

Olivier