mirror of https://github.com/kidoman/embd
367 lines
8.0 KiB
Go
367 lines
8.0 KiB
Go
// Package i2c enables gophers i2c speaking ability.
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package i2c
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import (
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"fmt"
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"os"
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"reflect"
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"sync"
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"syscall"
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"time"
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"unsafe"
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)
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const (
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delay = 20
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slaveCmd = 0x0703 // Cmd to set slave address
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rdrwCmd = 0x0707 // Cmd to read/write data together
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rd = 0x0001
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)
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// A Bus implements access to the I2C two wire bus.
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type Bus interface {
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// ReadByte reads a byte from the given address.
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ReadByte(addr byte) (value byte, err error)
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// WriteByte writes a byte to the given address.
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WriteByte(addr, value byte) error
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// WriteBytes writes a slice bytes to the given address.
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WriteBytes(addr byte, value []byte) error
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// ReadFromReg reads n (len(value)) bytes from the given address and register.
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ReadFromReg(addr, reg byte, value []byte) error
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// ReadByteFromReg reads a byte from the given address and register.
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ReadByteFromReg(addr, reg byte) (value byte, err error)
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// ReadU16FromReg reads a unsigned 16 bit integer from the given address and register.
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ReadWordFromReg(addr, reg byte) (value uint16, err error)
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// WriteToReg writes len(value) bytes to the given address and register.
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WriteToReg(addr, reg byte, value []byte) error
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// WriteByteToReg writes a byte to the given address and register.
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WriteByteToReg(addr, reg, value byte) error
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// WriteU16ToReg
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WriteWordToReg(addr, reg byte, value uint16) error
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}
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type i2c_msg struct {
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addr uint16
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flags uint16
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len uint16
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buf uintptr
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}
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type i2c_rdwr_ioctl_data struct {
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msgs uintptr
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nmsg uint32
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}
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var busMap map[byte]*bus
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var busMapLock sync.Mutex
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// Default instance of the i2c bus
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var Default Bus
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type bus struct {
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file *os.File
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addr byte
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mu sync.Mutex
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}
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func init() {
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busMap = make(map[byte]*bus)
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var err error
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Default, err = NewBus(1)
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if err != nil {
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panic(err)
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}
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}
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// NewBus creates a new I2C bus interface. The l variable
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// controls which bus we connect to.
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//
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// For the newer RaspberryPi, the number is 1 (earlier model uses 0.)
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func NewBus(l byte) (Bus, error) {
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busMapLock.Lock()
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defer busMapLock.Unlock()
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var b *bus
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if b = busMap[l]; b == nil {
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b = new(bus)
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var err error
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if b.file, err = os.OpenFile(fmt.Sprintf("/dev/i2c-%v", l), os.O_RDWR, os.ModeExclusive); err != nil {
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return nil, err
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}
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busMap[l] = b
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}
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return b, nil
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}
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func (b *bus) setAddress(addr byte) (err error) {
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if addr != b.addr {
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if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), slaveCmd, uintptr(addr)); errno != 0 {
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err = syscall.Errno(errno)
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return
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}
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b.addr = addr
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}
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return
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}
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func (b *bus) ReadByte(addr byte) (value byte, err error) {
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b.mu.Lock()
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defer b.mu.Unlock()
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if err = b.setAddress(addr); err != nil {
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return
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}
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bytes := make([]byte, 1)
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n, err := b.file.Read(bytes)
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if n != 1 {
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err = fmt.Errorf("i2c: Unexpected number (%v) of bytes read", n)
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}
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value = bytes[0]
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return
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}
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func (b *bus) WriteByte(addr, value byte) (err error) {
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b.mu.Lock()
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defer b.mu.Unlock()
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if err = b.setAddress(addr); err != nil {
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return
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}
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n, err := b.file.Write([]byte{value})
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if n != 1 {
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err = fmt.Errorf("i2c: Unexpected number (%v) of bytes written in WriteByte", n)
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}
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return
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}
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func (b *bus) WriteBytes(addr byte, value []byte) error {
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b.mu.Lock()
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defer b.mu.Unlock()
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if err := b.setAddress(addr); err != nil {
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return err
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}
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for i := range value {
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n, err := b.file.Write([]byte{value[i]})
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if n != 1 {
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return fmt.Errorf("i2c: Unexpected number (%v) of bytes written in WriteBytes", n)
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}
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if err != nil {
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return err
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}
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time.Sleep(delay * time.Millisecond)
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}
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return nil
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}
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func (b *bus) ReadFromReg(addr, reg byte, value []byte) (err error) {
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b.mu.Lock()
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defer b.mu.Unlock()
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if err = b.setAddress(addr); err != nil {
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return
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}
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hdrp := (*reflect.SliceHeader)(unsafe.Pointer(&value))
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var messages [2]i2c_msg
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messages[0].addr = uint16(addr)
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messages[0].flags = 0
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messages[0].len = 1
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messages[0].buf = uintptr(unsafe.Pointer(®))
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messages[1].addr = uint16(addr)
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messages[1].flags = rd
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messages[1].len = uint16(len(value))
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messages[1].buf = uintptr(unsafe.Pointer(hdrp.Data))
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var packets i2c_rdwr_ioctl_data
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packets.msgs = uintptr(unsafe.Pointer(&messages))
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packets.nmsg = 2
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if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), rdrwCmd, uintptr(unsafe.Pointer(&packets))); errno != 0 {
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return syscall.Errno(errno)
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}
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return nil
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}
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func (b *bus) ReadByteFromReg(addr, reg byte) (value byte, err error) {
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buf := make([]byte, 1)
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if err = b.ReadFromReg(addr, reg, buf); err != nil {
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return
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}
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value = buf[0]
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return
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}
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func (b *bus) ReadWordFromReg(addr, reg byte) (value uint16, err error) {
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buf := make([]byte, 2)
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if err = b.ReadFromReg(addr, reg, buf); err != nil {
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return
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}
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value = uint16((uint16(buf[0]) << 8) | uint16(buf[1]))
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return
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}
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func (b *bus) WriteToReg(addr, reg byte, value []byte) (err error) {
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b.mu.Lock()
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defer b.mu.Unlock()
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if err = b.setAddress(addr); err != nil {
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return
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}
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outbuf := append([]byte{reg}, value...)
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hdrp := (*reflect.SliceHeader)(unsafe.Pointer(&outbuf))
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var message i2c_msg
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message.addr = uint16(addr)
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message.flags = 0
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message.len = uint16(len(outbuf))
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message.buf = uintptr(unsafe.Pointer(&hdrp.Data))
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var packets i2c_rdwr_ioctl_data
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packets.msgs = uintptr(unsafe.Pointer(&message))
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packets.nmsg = 1
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if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), rdrwCmd, uintptr(unsafe.Pointer(&packets))); errno != 0 {
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err = syscall.Errno(errno)
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return
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}
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return
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}
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func (b *bus) WriteByteToReg(addr, reg, value byte) (err error) {
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b.mu.Lock()
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defer b.mu.Unlock()
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if err = b.setAddress(addr); err != nil {
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return
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}
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outbuf := [...]byte{
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reg,
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value,
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}
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var message i2c_msg
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message.addr = uint16(addr)
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message.flags = 0
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message.len = uint16(len(outbuf))
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message.buf = uintptr(unsafe.Pointer(&outbuf))
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var packets i2c_rdwr_ioctl_data
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packets.msgs = uintptr(unsafe.Pointer(&message))
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packets.nmsg = 1
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if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), rdrwCmd, uintptr(unsafe.Pointer(&packets))); errno != 0 {
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err = syscall.Errno(errno)
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return
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}
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return
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}
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func (b *bus) WriteWordToReg(addr, reg byte, value uint16) (err error) {
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b.mu.Lock()
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defer b.mu.Unlock()
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if err = b.setAddress(addr); err != nil {
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return
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}
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outbuf := [...]byte{
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reg,
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byte(value >> 8),
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byte(value),
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}
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var messages i2c_msg
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messages.addr = uint16(addr)
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messages.flags = 0
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messages.len = uint16(len(outbuf))
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messages.buf = uintptr(unsafe.Pointer(&outbuf))
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var packets i2c_rdwr_ioctl_data
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packets.msgs = uintptr(unsafe.Pointer(&messages))
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packets.nmsg = 1
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if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), rdrwCmd, uintptr(unsafe.Pointer(&packets))); errno != 0 {
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err = syscall.Errno(errno)
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return
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}
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return
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}
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// ReadByte reads a byte from the given address.
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func ReadByte(addr byte) (value byte, err error) {
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return Default.ReadByte(addr)
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}
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// WriteByte writes a byte to the given address.
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func WriteByte(addr, value byte) error {
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return Default.WriteByte(addr, value)
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}
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// WriteBytes writes a slice bytes to the given address.
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func WriteBytes(addr byte, value []byte) error {
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return Default.WriteBytes(addr, value)
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}
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// ReadFromReg reads n (len(value)) bytes from the given address and register.
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func ReadFromReg(addr, reg byte, value []byte) error {
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return Default.ReadFromReg(addr, reg, value)
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}
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// ReadByteFromReg reads a byte from the given address and register.
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func ReadByteFromReg(addr, reg byte) (value byte, err error) {
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return Default.ReadByteFromReg(addr, reg)
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}
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// ReadU16FromReg reads a unsigned 16 bit integer from the given address and register.
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func ReadWordFromReg(addr, reg byte) (value uint16, err error) {
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return Default.ReadWordFromReg(addr, reg)
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}
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// WriteToReg writes len(value) bytes to the given address and register.
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func WriteToReg(addr, reg byte, value []byte) error {
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return Default.WriteToReg(addr, reg, value)
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}
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// WriteByteToReg writes a byte to the given address and register.
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func WriteByteToReg(addr, reg, value byte) error {
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return Default.WriteByteToReg(addr, reg, value)
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}
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// WriteU16ToReg
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func WriteWordToReg(addr, reg byte, value uint16) error {
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return Default.WriteWordToReg(addr, reg, value)
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}
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