Parallel Port?

Todd Zuercher wrote:

I am just curious, why is EMC only able to use parallel port pins 1,14,16, and 17 only as outputs? The reason I ask is because we have sever older CNCs running some old DOS software that do use each of those pins as inputs for limit switches. It would make converting them to EMC a bit simpler if I didn't have to make my own cables to run them. It would also be nice to beable to devide the number of ins and outs on one port more evenly. (if I could have 8 of each on one port, then I could get by with one instead of two.)

Some specific parallel ports have open collector outputs, which can be forced low and the values read.
This is outside the p-port spec, and is not something that the EMC2 driver can afford to assume is safe.

It ought to be possible to change hal_parport to read those pins, if you want to.

It may be undocumented, but there is experimental support for these four pins being inputs in the hal_parport driver. This is called "X" mode, and to get it, instead of specifying I/in or O/out, specify X for the direction. This gives 8 outputs and 9 inputs, a very nice mix.

Be aware it only works on some parallel ports (hardware limitation) and the driver code has probably not received much testing in the years since it was put in. The comments in the code call it experimental. Please report back with your success/failure if you try it.

I am curious, does mode X work for you?