all: update NewAdvertisementInterval to accept time.Duration

This makes the API a bit more natural and (if needed) allows for a
slightly greater precision in specifying the advertisement interval.

examples/advertisement/main.go

@@ -13,7 +13,7 @@ func main() {
 	adv := adapter.DefaultAdvertisement()
 	must("config adv", adv.Configure(bluetooth.AdvertisementOptions{
 		LocalName: "Go Bluetooth",
-		Interval:  bluetooth.NewAdvertisementInterval(100),
+		Interval:  bluetooth.NewAdvertisementInterval(100 * time.Millisecond),
 	}))
 	must("start adv", adv.Start())
 

examples/heartrate/main.go

@@ -18,7 +18,7 @@ func main() {
 	must("config adv", adv.Configure(bluetooth.AdvertisementOptions{
 		LocalName:    "Go HRS",
 		ServiceUUIDs: []bluetooth.UUID{bluetooth.New16BitUUID(0x2A37)},
-		Interval:     bluetooth.NewAdvertisementInterval(100),
+		Interval:     bluetooth.NewAdvertisementInterval(100 * time.Millisecond),
 	}))
 	must("start adv", adv.Start())
 

examples/ledcolor/main.go

@@ -25,7 +25,7 @@ func main() {
 	adv := adapter.DefaultAdvertisement()
 	must("config adv", adv.Configure(bluetooth.AdvertisementOptions{
 		LocalName: "LED colors",
-		Interval:  bluetooth.NewAdvertisementInterval(100),
+		Interval:  bluetooth.NewAdvertisementInterval(100 * time.Millisecond),
 	}))
 	must("start adv", adv.Start())
 

examples/nusserver/main.go

@@ -8,6 +8,8 @@ package main
 // Code to interact with a raw terminal is in separate files with build tags.
 
 import (
+	"time"
+
 	"github.com/tinygo-org/bluetooth"
 )
 
@@ -25,7 +27,7 @@ func main() {
 	must("config adv", adv.Configure(bluetooth.AdvertisementOptions{
 		LocalName:    "NUS", // Nordic UART Service
 		ServiceUUIDs: []bluetooth.UUID{serviceUUID},
-		Interval:     bluetooth.NewAdvertisementInterval(100),
+		Interval:     bluetooth.NewAdvertisementInterval(100 * time.Millisecond),
 	}))
 	must("start adv", adv.Start())
 

gap.go

@@ -1,6 +1,9 @@
 package bluetooth
 
-import "errors"
+import (
+	"errors"
+	"time"
+)
 
 var (
 	errScanning                  = errors.New("bluetooth: a scan is already in progress")
@@ -28,11 +31,12 @@ type AdvertisementOptions struct {
 // AdvertisementInterval is the advertisement interval in 0.625µs units.
 type AdvertisementInterval uint32
 
-// NewAdvertisementInterval returns a new advertisement interval, based on an
-// interval in milliseconds.
-func NewAdvertisementInterval(intervalMillis uint32) AdvertisementInterval {
-	// Convert an interval to units of
-	return AdvertisementInterval(intervalMillis * 8 / 5)
+// NewAdvertisementInterval returns a new advertisement interval. Advertisement
+// intervals are in units of 0.625µs, so the precision will not be greater than
+// that.
+func NewAdvertisementInterval(interval time.Duration) AdvertisementInterval {
+	// Convert an interval to units of 0.625µs.
+	return AdvertisementInterval(uint64(interval / (625 * time.Microsecond)))
 }
 
 // Connection is a numeric identifier that indicates a connection handle.

gap_nrf528xx.go

@@ -5,6 +5,7 @@ package bluetooth
 import (
 	"device/arm"
 	"runtime/volatile"
+	"time"
 )
 
 /*
@@ -86,8 +87,8 @@ func (a *Adapter) Scan(callback func(*Adapter, ScanResult)) error {
 	scanParams := C.ble_gap_scan_params_t{}
 	scanParams.set_bitfield_extended(0)
 	scanParams.set_bitfield_active(0)
-	scanParams.interval = 100 * 1000 / 625 // 100ms in 625µs units
-	scanParams.window = 100 * 1000 / 625   // 100ms in 625µs units
+	scanParams.interval = uint16(NewAdvertisementInterval(100 * time.Millisecond))
+	scanParams.window = uint16(NewAdvertisementInterval(100 * time.Millisecond))
 	scanParams.timeout = C.BLE_GAP_SCAN_TIMEOUT_UNLIMITED
 	scanReportBufferInfo := C.ble_data_t{
 		p_data: &scanReportBuffer.data[0],