Started on rpi gpio library

README.md

@@ -1,4 +1,7 @@
 go-rpio
 =======
 
-Raspberry Pi GPIO library for go-lang
+Raspberry Pi GPIO library for go-lang with limited functionality
+Native, no c libraries needed.
+
+Work in progress

rpio/rpio.go

@@ -0,0 +1,151 @@
+package rpio
+
+import (
+	"fmt"
+	"os"
+	"reflect"
+	"sync"
+	"syscall"
+	"unsafe"
+)
+
+type Direction uint8
+type Pin uint8
+type State uint8
+
+// Memory offsets for gpio, see the spec for more details
+// http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
+const (
+	bcm2835Base = 0x20000000
+	gpioBase    = bcm2835Base + 0x200000
+
+	pinmask uint32 = 7 // 0b111
+)
+
+// Pin modes (input, output)
+const (
+	INPUT Direction = iota
+	OUTPUT
+)
+
+// State of pin, high/low
+const (
+	LOW State = iota
+	HIGH
+)
+
+var (
+	mem     []uint32
+	mem8    []uint8
+	memlock sync.Mutex
+)
+
+func (pin Pin) High() {
+	WritePin(uint8(pin), HIGH)
+}
+
+func (pin Pin) Low() {
+	WritePin(uint8(pin), LOW)
+}
+
+func (pin Pin) Mode(dir Direction) {
+	PinMode(uint8(pin), dir)
+}
+
+func (pin Pin) Write(state State) {
+	WritePin(uint8(pin), state)
+}
+
+func (pin Pin) Read() State {
+	return ReadPin(uint8(pin))
+}
+
+func PinMode(pin uint8, direction Direction) {
+	fsel := pin / 10
+	shift := (pin % 10) * 3
+
+	fmt.Println(pin, fsel, shift)
+	fmt.Printf("0b%b  \n", mem[fsel])
+
+	memlock.Lock()
+
+	if direction == INPUT {
+		fmt.Printf("0b%b\n\n", mem[fsel]&^(pinmask<<shift))
+	} else {
+		fmt.Printf("0b%b\n\n", mem[fsel]&^(pinmask<<shift)|(1<<shift))
+	}
+
+	memlock.Unlock()
+}
+
+func WritePin(pin uint8, state State) {
+
+	clearReg := pin/32 + 10
+	setReg := pin/32 + 7
+
+	memlock.Lock()
+
+	if state == LOW {
+		fmt.Printf("0b%b  \n", mem[clearReg])
+		fmt.Printf("0b%b\n\n", 1<<(pin&31))
+	} else {
+		fmt.Printf("0b%b  \n", mem[setReg])
+		fmt.Printf("0b%b\n\n", 1<<(pin&31))
+	}
+
+	memlock.Unlock()
+}
+
+func ReadPin(pin uint8) State {
+	// input level register offset
+	levelReg := pin/32 + 13
+
+	//memlock.Lock()
+	fmt.Printf("0b%b  \n", mem[levelReg])
+	fmt.Printf("0b%b  \n", mem[levelReg]&(1<<pin))
+
+	if (mem[levelReg] & (1 << pin)) != 0 {
+		return HIGH
+	}
+
+	return LOW
+}
+
+func Open() (err error) {
+	var file *os.File
+
+	// Open fd for rw mem access
+	file, err = os.OpenFile("/dev/mem", os.O_RDWR|os.O_SYNC, 0)
+	if err != nil {
+		return
+	}
+
+	// Can be closed after memory mapping
+	defer file.Close()
+
+	memlock.Lock()
+
+	// Memory map GPIO registers to byte array
+	mem8, err = syscall.Mmap(int(file.Fd()), gpioBase, 4*1024, syscall.PROT_READ, syscall.MAP_SHARED)
+	if err != nil {
+		return
+	}
+
+	// Convert mapped byte memory to unsafe []uint32 pointer, adjust length as needed
+	header := *(*reflect.SliceHeader)(unsafe.Pointer(&mem8))
+	header.Len /= (32 / 8) // (32 bit = 4 bytes)
+	header.Cap /= (32 / 8)
+
+	mem = *(*[]uint32)(unsafe.Pointer(&header))
+
+	memlock.Unlock()
+
+	return nil
+}
+
+func Close() {
+	// Unmap memory
+	memlock.Lock()
+	syscall.Munmap(mem8)
+	memlock.Unlock()
+}