This extension uses C functions from FreeBSD's ppi to implement simple procedures for handling Parallel Port's input and output. [procedure] (ppi-in DEVICE REQUEST) gets the contents of the corresponding register on the given device [procedure] (ppi-out DEVICE REQUEST NUMBER) sets the contents of the corresponding register on the given device where DEVICE is a string indicating a path to the device's file (eg. "/dev/ppi0") REQUEST is one of PPIGDATA PPISDATA PPIGSTATUS PPISSTATUS PPIGCTRL PPISCTRL PPIGEPPD PPISEPPD PPIGEPPA PPISEPPA PPIGECR PPISECR PPIGFIFO PPISFIFO with a meaning as described in man ppi. There are predefined procedures to set and get various registers ppi-data-in ppi-data-out ppi-status-in ppi-status-out ppi-control-in ppi-control-out ppi-eppd-in ppi-eppd-out ppi-eppa-in ppi-eppa-out ppi-ecr-in ppi-ecr-out ppi-fifo-in ppi-fifo-out Each ppi-***-in procedure is a procedure of no arguments. Each ppi-***-out procedure is a procedure of one argument being the number to send to register. For example: [procedure] (ppi-data-out NUMBER) sets the contents of the data register to given number There are 8 bits in the data register so range of numbers available to set is 0 - 255 Example : (ppi-data-out 5) sets D2 and D0 to logical 1 [procedure] (ppi-status-in) -> 8 * S3 + 16 * S4 + 32 * S5 + 64 * S6 + 128 * ~S7 reads the contents of the status register. Example : For S3 and S5 set to 1 and the rest to 0 (ppi-status-in) -> 40 The predefined procedures make usage of the device /dev/ppi0 as the parallel port. If you want them to use another device, you can change it, as the device's name to use is bound with ppi-device variable. Example: To read control register on /dev/ppi1 device you can use either (ppi-in "/dev/ppi1" PPIGCTRL) or (set! ppi-device "/dev/ppi1") (ppi-control-in) In the latter case, consequent calls to ppi-***-in/out procedures will obviously refer to "/dev/ppi1" device. For further reference on ppi see 'man ppi' There are many sites devoted to parallel port operations, for example: http://www.beyondlogic.org/spp/parallel.htm http://www.doc.ic.ac.uk/~ih/doc/par/
Copyright (c) 2005 Michal Dybizbanski
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