add headamp gain and phantom commands

internal/xair/headamp.go

@@ -0,0 +1,67 @@
+package xair
+
+import "fmt"
+
+type HeadAmp struct {
+	baseAddress string
+	client      Client
+}
+
+func NewHeadAmp(c Client) *HeadAmp {
+	return &HeadAmp{
+		baseAddress: c.addressMap["headamp"],
+		client:      c,
+	}
+}
+
+// Gain gets the gain level for the specified headamp index.
+func (h *HeadAmp) Gain(index int) (float64, error) {
+	address := fmt.Sprintf(h.baseAddress, index) + "/gain"
+	err := h.client.SendMessage(address)
+	if err != nil {
+		return 0, err
+	}
+
+	resp := <-h.client.respChan
+	val, ok := resp.Arguments[0].(float32)
+	if !ok {
+		return 0, fmt.Errorf("unexpected argument type for headamp gain value")
+	}
+
+	return linGet(-12, 60, float64(val)), nil
+}
+
+// SetGain sets the gain level for the specified headamp index.
+func (h *HeadAmp) SetGain(index int, level float64) error {
+	address := fmt.Sprintf(h.baseAddress, index) + "/gain"
+	return h.client.SendMessage(address, float32(linSet(-12, 60, level)))
+}
+
+// PhantomPower gets the phantom power status for the specified headamp index.
+func (h *HeadAmp) PhantomPower(index int) (bool, error) {
+	address := fmt.Sprintf(h.baseAddress, index) + "/phantom"
+	err := h.client.SendMessage(address)
+	if err != nil {
+		return false, err
+	}
+
+	resp := <-h.client.respChan
+	val, ok := resp.Arguments[0].(int32)
+	if !ok {
+		return false, fmt.Errorf("unexpected argument type for phantom power value")
+	}
+
+	return val != 0, nil
+}
+
+// SetPhantomPower sets the phantom power status for the specified headamp index.
+func (h *HeadAmp) SetPhantomPower(index int, enabled bool) error {
+	address := fmt.Sprintf(h.baseAddress, index) + "/phantom"
+	var val int32
+	if enabled {
+		val = 1
+	} else {
+		val = 0
+	}
+	return h.client.SendMessage(address, val)
+}