Added SPI Library

samples/spi.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"fmt"
+	"github.com/kid0m4n/go-rpi/spi"
+)
+
+func main() {
+	var rx_data uint8
+
+	fmt.Println("Hello")
+
+	bus, _ := spi.NewSpiBus()
+
+	rx_data, _ = bus.TransferAndRecieveByteData(8`	)
+
+	fmt.Printf("Received %v \n", rx_data)
+}

spi/spi.go

@@ -0,0 +1,195 @@
+package spi
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"sync"
+	"syscall"
+	"unsafe"
+)
+
+const (
+	SPI_CPHA = 0x01
+	SPI_CPOL = 0x02
+
+	SPI_MODE_0 = (0 | 0)
+	SPI_MODE_1 = (0 | SPI_CPHA)
+	SPI_MODE_2 = (SPI_CPOL | 0)
+	SPI_MODE_3 = (SPI_CPOL | SPI_CPHA)
+
+	SPI_IOC_WR_MODE          = 0x40016B01
+	SPI_IOC_WR_BITS_PER_WORD = 0x40016B03
+	SPI_IOC_WR_MAX_SPEED_HZ  = 0x40046B04
+
+	SPI_IOC_RD_MODE          = 0x80016B01
+	SPI_IOC_RD_BITS_PER_WORD = 0x80016B03
+	SPI_IOC_RD_MAX_SPEED_HZ  = 0x80046B04
+
+	SPI_IOC_MESSAGE_0   = 1073769216 //0x40006B00
+	SPI_IOC_INCREMENTER = 2097152    //0x200000
+)
+
+type SpiBus interface {
+	TransferAndRecieveByteData(byte) (uint8, error)
+}
+
+type spiBus struct {
+	file *os.File
+	mode byte
+	mu   sync.Mutex
+}
+
+type spiMode struct {
+	mode uintptr
+}
+
+type spiIocTransfer struct {
+	tx_buf uint64
+	rx_buf uint64
+
+	length        uint32
+	speed_hz      uint32
+	delay_usecs   uint16
+	bits_per_word uint8
+}
+
+func spi_ioc_message_n(n uint32) uint32 {
+	return (SPI_IOC_MESSAGE_0 + (n * SPI_IOC_INCREMENTER))
+}
+
+func NewSpiBus() (SpiBus, error) {
+	var b *spiBus
+	var err error
+	b = new(spiBus)
+
+	fmt.Println("Opening SPI device.")
+	b.file, err = os.OpenFile("/dev/spidev0.1", os.O_EXCL, os.ModeExclusive)
+
+	if err != nil {
+		fmt.Print("spi: Could not open SPI device due to ")
+		fmt.Println(err.Error())
+		return nil, err
+	} else {
+		fmt.Println("spi: Successfully initialized spiBus")
+		fmt.Println("spi: File Fd = ", b.file.Fd())
+	}
+
+	var mode uint8
+	mode = 0
+	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), SPI_IOC_RD_MODE, uintptr(unsafe.Pointer(&mode)))
+
+	if errno != 0 {
+		fmt.Println(syscall.Errno(errno))
+		err = syscall.Errno(errno)
+		return nil, err
+	} else {
+		fmt.Println("Successfully read the mode")
+		fmt.Println(mode)
+	}
+
+	_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), SPI_IOC_WR_MODE, uintptr(unsafe.Pointer(&mode)))
+
+	if errno != 0 {
+		fmt.Println(syscall.Errno(errno))
+		err = syscall.Errno(errno)
+		return nil, err
+	} else {
+		fmt.Println("Successfully read the mode")
+		fmt.Println(mode)
+	}
+
+	var speed_max uint32
+	speed_max = 5000000
+	_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), SPI_IOC_RD_MAX_SPEED_HZ, uintptr(unsafe.Pointer(&speed_max)))
+
+	if errno != 0 {
+		fmt.Println(syscall.Errno(errno))
+		err = syscall.Errno(errno)
+		return nil, err
+	} else {
+		fmt.Println("Successfully read the speed")
+		fmt.Println(speed_max)
+	}
+
+	_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), SPI_IOC_WR_MAX_SPEED_HZ, uintptr(unsafe.Pointer(&speed_max)))
+
+	if errno != 0 {
+		fmt.Println(syscall.Errno(errno))
+		err = syscall.Errno(errno)
+		return nil, err
+	} else {
+		fmt.Println("Successfully read the speed")
+		fmt.Println(speed_max)
+	}
+
+	var bps uint32
+	bps = 8
+	_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), SPI_IOC_RD_BITS_PER_WORD, uintptr(unsafe.Pointer(&bps)))
+
+	if errno != 0 {
+		fmt.Println(syscall.Errno(errno))
+		err = syscall.Errno(errno)
+		return nil, err
+	} else {
+		fmt.Println("Successfully read the bps")
+		fmt.Println(bps)
+	}
+
+	_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), SPI_IOC_WR_BITS_PER_WORD, uintptr(unsafe.Pointer(&bps)))
+
+	if errno != 0 {
+		fmt.Println(syscall.Errno(errno))
+		err = syscall.Errno(errno)
+		return nil, err
+	} else {
+		fmt.Println("Successfully wrote the bps")
+		fmt.Println(bps)
+	}
+
+	var bpw uint32
+	bpw = 8
+	_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), SPI_IOC_RD_BITS_PER_WORD, uintptr(unsafe.Pointer(&bpw)))
+
+	if errno != 0 {
+		fmt.Println(syscall.Errno(errno))
+		err = syscall.Errno(errno)
+		return nil, err
+	} else {
+		fmt.Println("Successfully read the bpw")
+		fmt.Println(bpw)
+	}
+
+	_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), SPI_IOC_WR_BITS_PER_WORD, uintptr(unsafe.Pointer(&bpw)))
+
+	if errno != 0 {
+		fmt.Println(syscall.Errno(errno))
+		err = syscall.Errno(errno)
+		return nil, err
+	} else {
+		fmt.Println("Successfully read the bpw")
+		fmt.Println(bpw)
+	}
+
+	return b, err
+}
+
+func (b *spiBus) TransferAndRecieveByteData(tx_data uint8) (rx_data uint8, err error) {
+	var data spiIocTransfer
+
+	data.delay_usecs = 0
+	data.length = 8
+	data.speed_hz = 5000000
+	data.bits_per_word = 8
+	data.tx_buf = uint64(uintptr(unsafe.Pointer(&tx_data)))
+	data.rx_buf = uint64(uintptr(unsafe.Pointer(&rx_data)))
+
+	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), uintptr(spi_ioc_message_n(1)), uintptr(unsafe.Pointer(&data)))
+	if errno != 0 {
+		err = syscall.Errno(errno)
+		return 0, nil
+	}
+
+	log.Println("Successfully read the data")
+	return rx_data, nil
+}