forked from davecheney/rpi
/
gpio.go
66 lines (59 loc) · 1.57 KB
/
gpio.go
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package rpi
import (
"log"
"syscall"
"unsafe"
)
var (
gpfsel, gpset, gpclr, gplev []*uint32
)
func initGPIO(memfd int) {
buf, err := syscall.Mmap(memfd, BCM2835_GPIO_BASE, BCM2835_BLOCK_SIZE, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
if err != nil {
log.Fatalf("rpi: unable to mmap GPIO page: %v", err)
}
gpfsel = []*uint32{
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPFSEL0])),
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPFSEL1])),
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPFSEL2])),
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPFSEL3])),
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPFSEL4])),
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPFSEL5])),
}
gpset = []*uint32{
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPSET0])),
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPSET1])),
}
gpclr = []*uint32{
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPCLR0])),
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPCLR1])),
}
gplev = []*uint32{
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPLEV0])),
(*uint32)(unsafe.Pointer(&buf[BCM2835_GPLEV1])),
}
}
func GPIOSet(pin uint8) {
offset := pin / 32
shift := pin % 32
*gpset[offset] = (1 << shift)
}
func GPIOClear(pin uint8) {
offset := pin / 32
shift := pin % 32
*gpclr[offset] = (1 << shift)
}
func GPIOGet(pin uint8) bool {
offset := pin / 32
shift := pin % 32
return *gplev[offset]&(1<<shift) == (1 << shift)
}
func GPIOFSel(pin, mode uint8) {
offset := pin / 10
shift := (pin % 10) * 3
value := *gpfsel[offset]
mask := BCM2835_GPIO_FSEL_MASK << shift
value &= ^uint32(mask)
value |= uint32(mode) << shift
*gpfsel[offset] = value & mask
}