87 lines
1.6 KiB
Go
87 lines
1.6 KiB
Go
package serial
|
|
|
|
import (
|
|
"errors"
|
|
"sync"
|
|
"time"
|
|
|
|
"go.bug.st/serial"
|
|
)
|
|
|
|
const portDev = "/dev/ttyUSB0"
|
|
const maxAddr = 1 << 17
|
|
|
|
type Serial struct {
|
|
portMu sync.Mutex
|
|
port serial.Port
|
|
}
|
|
|
|
func Open() (*Serial, error) {
|
|
mode := &serial.Mode{
|
|
BaudRate: 115_200,
|
|
}
|
|
port, err := serial.Open(portDev, mode)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
return &Serial{port: port}, nil
|
|
}
|
|
|
|
func (d *Serial) Close() error {
|
|
d.portMu.Lock()
|
|
defer d.portMu.Unlock()
|
|
return d.port.Close()
|
|
}
|
|
|
|
func encode(addr int, write bool, data byte) [4]byte {
|
|
writeVal := uint8(0)
|
|
if write {
|
|
writeVal = 1
|
|
}
|
|
var ret [4]byte
|
|
ret[3] = data
|
|
ret[2] = byte(addr<<1) | writeVal
|
|
ret[1] = byte(addr >> 7)
|
|
ret[0] = byte(addr >> 15)
|
|
return ret
|
|
}
|
|
|
|
func (d *Serial) ReadAt(bs []byte, off int64) (int, error) {
|
|
d.portMu.Lock()
|
|
defer d.portMu.Unlock()
|
|
if off+int64(len(bs)) >= maxAddr {
|
|
return 0, errors.New("OOB read")
|
|
}
|
|
for i := range bs {
|
|
packet := encode(int(off)+i, false, 0)
|
|
if _, err := d.port.Write(packet[:]); err != nil {
|
|
return i, err
|
|
}
|
|
d.port.SetReadTimeout(2 * time.Second)
|
|
n, err := d.port.Read(packet[:1])
|
|
if err != nil {
|
|
return i, err
|
|
} else if n == 0 {
|
|
return i, errors.New("short read")
|
|
}
|
|
bs[i] = packet[0]
|
|
}
|
|
return len(bs), nil
|
|
}
|
|
|
|
func (d *Serial) WriteAt(bs []byte, off int64) (int, error) {
|
|
d.portMu.Lock()
|
|
defer d.portMu.Unlock()
|
|
if off+int64(len(bs)) >= maxAddr {
|
|
return 0, errors.New("OOB write")
|
|
}
|
|
for i, v := range bs {
|
|
packet := encode(int(off)+i, true, v)
|
|
if _, err := d.port.Write(packet[:]); err != nil {
|
|
return i, err
|
|
}
|
|
}
|
|
return len(bs), nil
|
|
}
|