Update to use DiscoverServiceEvent, DiscoverCharacteristicEvent, and

UpdateValue event.

main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/binary"
 	"fmt"
 	"io/ioutil"
 	"log"
@@ -49,6 +50,15 @@ func main() {
 	app.Main()
 }
 
+func hrDecode(x []byte) int {
+	flags := x[0]
+	if flags&0x80 != 0 { // uint16 format
+		return int(binary.BigEndian.Uint16(x[1:2]))
+	} else {
+		return int(x[1])
+	}
+}
+
 func eventloop() {
 	w := app.NewWindow(
 		app.Size(unit.Dp(400), unit.Dp(400)),
@@ -69,6 +79,7 @@ func eventloop() {
 	b := ble.NewBLE()
 
 	state := "starting"
+	var hr int
 	var periph ble.Peripheral
 	periphs := make([]ble.Peripheral, 0)
 	btns := make([]*widget.Button, 0)
@@ -131,7 +142,7 @@ func eventloop() {
 			th.Body1(periph.Name).Layout(gtx)
 		})
 		c3 := f.Rigid(gtx, func() {
-			l := th.H1(fmt.Sprintf("%d", b.HR()))
+			l := th.H1(fmt.Sprintf("%d", hr))
 			l.Alignment = text.Middle
 			l.Layout(gtx)
 		})
@@ -162,7 +173,7 @@ func eventloop() {
 					}
 				}
 				w.Invalidate()
-			case ble.DiscoverEvent:
+			case ble.DiscoverPeripheralEvent:
 				fmt.Printf("found %s\n", e.Peripheral.Identifier)
 				periphs = append(periphs, e.Peripheral)
 				btns = append(btns, &widget.Button{})
@@ -173,7 +184,7 @@ func eventloop() {
 				fmt.Printf("Connect event\n")
 				state = "connected"
 				periph = e.Peripheral
-				ble.DiscoverServices(e.Peripheral)
+				e.Peripheral.DiscoverServices()
 				page = hrpage
 				w.Invalidate()
 			case ble.ConnectTimeoutEvent:
@@ -183,6 +194,20 @@ func eventloop() {
 				page = scanpage
 				b.Scan()
 				w.Invalidate()
+			case ble.DiscoverServiceEvent:
+				fmt.Printf("DiscoverService %s\n", e.Gatt.UUID)
+				if e.Gatt.UUID == "180D" {
+					fmt.Printf("Found HRM Service\n")
+					e.Peripheral.DiscoverCharacteristics(e.Service)
+				}
+			case ble.DiscoverCharacteristicEvent:
+				fmt.Printf("DiscoverCharacteristic %s\n", e.Gatt.UUID)
+				if e.Gatt.UUID == "2A37" {
+					fmt.Printf("Found heart rate value\n")
+					e.Peripheral.SetNotifyValue(e.Characteristic)
+				}
+			case ble.UpdateValueEvent:
+				hr = hrDecode(e.Data)
 			}
 		case <-tick.C:
 			w.Invalidate()