ref: 75c92428225428c8fde2d015f010e608a0b12f1d
dir: purgatorio/man/3/gpio
.TH GPIO 3 SA1100 .SH NAME gpio \- access to GPIO registers .SH SYNOPSIS .B bind -a .B #G .B /dev .PP .nf .B /dev/gpioclear .B /dev/gpioctl .B /dev/gpioedge .B /dev/gpioset .B /dev/gpiostatus .fi .SH DESCRIPTION .PP The GPIO interface serves a one-level directory with five files that give access to the GPIO registers in the SA1100. See the SA1100 handbook for details of the function of the various registers. .PP The control file .B gpioctl accepts commands to set individual bits in the edge detect registers. Each control message has three space-separated fields: .IP .EX .I "reg pin value" .EE .LP where .I reg is a single character denoting a register, .I pin a bit within it, and .I val the value (0 or 1) for that bit. Valid choices for .I reg are: .B d (GPDR), .B r (GRER), .B f (GFER), and .B a (GAFR). For example, the control message .IP .EX d 10 1 .EE .LP sets bit 10 (following the handbook's bit-numbering conventions) in the GPIO pin direction register GPDR. .PP The read-only file .B gpiostatus shows the names and values (in hexadecimal) of all GPIO registers. .PP The remaining data files allow bits to be read by .B Sys->read requests and set by .B Sys->write requests. When read, each file returns the value of a given register as a single 8 digit hexadecimal number: .B gpioset and .B gpioclear both give the value of the level register, GPLR; and .B gpioedge gives the value of the edge dectect register, GEDR. Each write request should present a single number in textual form, which is assumed to be hexadecimal by default. The value is written to a GPIO register: .B gpioset corresponds to GPSR, .B gpioclear corresponds to GPCR, and .B gpioedge corresponds to GEDR. .SH SOURCE .B /os/sa1100/devgpio.c