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megapi: use serialport adaptor and move driver to drivers/serial
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,130 @@ | ||
package megapi | ||
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import ( | ||
"bytes" | ||
"encoding/binary" | ||
"log" | ||
"sync" | ||
"time" | ||
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"gobot.io/x/gobot/v2" | ||
"gobot.io/x/gobot/v2/drivers/serial" | ||
) | ||
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var _ gobot.Driver = (*MotorDriver)(nil) | ||
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type megapiMotorSerialAdaptor interface { | ||
gobot.Adaptor | ||
serial.SerialWriter | ||
} | ||
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// MotorDriver represents a motor | ||
type MotorDriver struct { | ||
*serial.Driver | ||
port byte | ||
halted bool | ||
writeBytesChannel chan []byte | ||
finalizeChannel chan struct{} | ||
syncRoot *sync.Mutex | ||
} | ||
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// NewMotorDriver creates a new MotorDriver at the given port | ||
func NewMotorDriver(a megapiMotorSerialAdaptor, port byte, opts ...serial.OptionApplier) *MotorDriver { | ||
d := &MotorDriver{ | ||
port: port, | ||
halted: true, | ||
syncRoot: &sync.Mutex{}, | ||
writeBytesChannel: make(chan []byte), | ||
finalizeChannel: make(chan struct{}), | ||
} | ||
d.Driver = serial.NewDriver(a, "MegaPiMotor", d.initialize, d.shutdown, opts...) | ||
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return d | ||
} | ||
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// Speed sets the motors speed to the specified value | ||
func (d *MotorDriver) Speed(speed int16) error { | ||
d.syncRoot.Lock() | ||
defer d.syncRoot.Unlock() | ||
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if d.halted { | ||
return nil | ||
} | ||
return d.speedHelper(speed) | ||
} | ||
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// initialize implements the Driver interface | ||
func (d *MotorDriver) initialize() error { | ||
d.syncRoot.Lock() | ||
defer d.syncRoot.Unlock() | ||
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// sleeping is required to give the board a chance to reset after connection is done | ||
time.Sleep(2 * time.Second) | ||
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// kick off thread to send bytes to the board | ||
go func() { | ||
for { | ||
select { | ||
case bytes := <-d.writeBytesChannel: | ||
if _, err := d.adaptor().SerialWrite(bytes); err != nil { | ||
panic(err) | ||
} | ||
time.Sleep(10 * time.Millisecond) | ||
case <-d.finalizeChannel: | ||
d.finalizeChannel <- struct{}{} | ||
return | ||
default: | ||
time.Sleep(10 * time.Millisecond) | ||
} | ||
} | ||
}() | ||
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d.halted = false | ||
return d.speedHelper(0) | ||
} | ||
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// Halt terminates the Driver interface | ||
func (d *MotorDriver) shutdown() error { | ||
d.syncRoot.Lock() | ||
defer d.syncRoot.Unlock() | ||
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d.finalizeChannel <- struct{}{} | ||
<-d.finalizeChannel | ||
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d.halted = true | ||
return d.speedHelper(0) | ||
} | ||
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// there is some sort of bug on the hardware such that you cannot | ||
// send the exact same speed to 2 different motors consecutively | ||
// hence we ensure we always alternate speeds | ||
func (d *MotorDriver) speedHelper(speed int16) error { | ||
if err := d.sendSpeed(speed - 1); err != nil { | ||
return err | ||
} | ||
return d.sendSpeed(speed) | ||
} | ||
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// sendSpeed sets the motors speed to the specified value | ||
func (d *MotorDriver) sendSpeed(speed int16) error { | ||
bufOut := new(bytes.Buffer) | ||
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// byte sequence: 0xff, 0x55, id, action, device, port | ||
bufOut.Write([]byte{0xff, 0x55, 0x6, 0x0, 0x2, 0xa, d.port}) | ||
if err := binary.Write(bufOut, binary.LittleEndian, speed); err != nil { | ||
return err | ||
} | ||
bufOut.Write([]byte{0xa}) | ||
d.writeBytesChannel <- bufOut.Bytes() | ||
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return nil | ||
} | ||
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func (d *MotorDriver) adaptor() megapiMotorSerialAdaptor { | ||
if a, ok := d.Connection().(megapiMotorSerialAdaptor); ok { | ||
return a | ||
} | ||
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log.Printf("%s has no MegaPi serial connector\n", d.Name()) | ||
return nil | ||
} |
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