Michael Haberler wrote: > > however, I dont see a good reason why there cannot be a hal_parport component > which works in "simulator" mode, and I'm just integrating a 'parapin' library > into hal_parport.* to create such a driver; parapin being created by a > certain Mr John Elson. Not done, but havent hit a roadblock yet. > > It is???? First I've heard of it. Well, there's no reason you can't control various hardware in user-mode, with the correct privileges. As long as you don't need true real-time performance, there's no reason to not do this. I have a diagnostic program for my boards that runs in user-mode and does essentially the same functions as LinuxCNC's hal_ppmc.c driver for testing motion control boards. > here comes your "Linuxcnc on a Raspberry pi" ;) (provided somebody hacks a > driver for the GPIO pins there) - appalling RT performance but a great > sprinkler system; fine as long as folks understand what they are getting into > in terms of latency > I've already done most of this (hardware and software) to get a small piece of this diag program working on the Beagle Board. ARM processors have a lot of complex features on GPIO pins (input, output drivers, pull-ups, pull-downs, edge detectors, set bit, clear bit, etc.) so they are a lot more complex than the PC parallel port. Also, mixed in an I/O bank with user-accessible pins are some system critical pins that you have to avoid altering or the system crashes. The set and clear bit functions are good for that.
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