Fully functional ant+ to bluetooth bridge.

cmd/bridge/ant.go

@@ -27,7 +27,8 @@ func resetAndWait(drv io.ReadWriter) error {
 	}
 }
 
-func listenForAntDevice(vendorId gousb.ID, productId gousb.ID, deviceNumber uint32) {
+func ListenForTrainer(vendorId gousb.ID, productId gousb.ID, deviceNumber uint32,
+	events chan<- Event) {
 	drv, err := usb.GetDevice(vendorId, productId)
 	if err != nil {
 		panic(err)
@@ -58,9 +59,18 @@ func listenForAntDevice(vendorId gousb.ID, productId gousb.ID, deviceNumber uint
 
 		switch msg.DeviceType() {
 		case ant.DEVICE_TYPE_POWER:
+			// Check data page first
+			page := msg[4] & 0x7F // mask toggle bit
+			if page != 0x10 {
+				continue
+			}
 			cur := ant.PowerMessage(msg)
 			fmt.Printf("%v: power: %dW  cadence: %d rpm\n",
 				msg.DeviceNumber(), cur.InstantaneousPower(), cur.InstantaneousCadence())
+			events <- Event{
+				Power:   cur.InstantaneousPower(),
+				Cadence: cur.InstantaneousCadence(),
+			}
 		}
 	}
 }

cmd/bridge/bluetooth.go

@@ -17,7 +17,7 @@ func must(err error) {
 	}
 }
 
-func ExposeBluetooth() {
+func ExposeBluetooth(events <-chan Event) {
 	must(adapter.Enable())
 
 	var powerChar bluetooth.Characteristic
@@ -49,14 +49,13 @@ func ExposeBluetooth() {
 	var lastCompletedRev float64 // time in 1/1024s of last completed revolution
 	lastUpdate := time.Now()
 	var elapsedTicks float64
-	for {
+	for event := range events {
 		now := time.Now()
 		deltaT := now.Sub(lastUpdate).Seconds()
 		lastUpdate = now
 
-		sec := now.Second()
-		watts := uint16(100 + sec)
-		rpm := float64(50 + sec)
+		watts := event.Power
+		rpm := float64(event.Cadence)
 
 		totalRevs += rpm / 60.0 * deltaT
 		elapsedTicks += deltaT * 1024.0
@@ -77,7 +76,5 @@ func ExposeBluetooth() {
 		powerChar.Write(payload)
 		fmt.Printf("watts: %d  rpm: %.0f  completedRevs: %.0f  lastRevTime: %.0f\n",
 			watts, rpm, completedRevs, lastCompletedRev)
-
-		time.Sleep(250 * time.Millisecond)
 	}
 }

cmd/bridge/event.go

@@ -0,0 +1,6 @@
+package main
+
+type Event struct {
+	Power   uint16
+	Cadence uint8
+}

cmd/bridge/main.go

@@ -1,26 +1,20 @@
 package main
 
 import (
-	"fmt"
 	"os/exec"
 
 	"github.com/google/gousb"
 )
 
-func oldMain() {
+func main() {
+	exec.Command("hciconfig", "hci0", "down").Run()
+	exec.Command("hciconfig", "hci0", "up").Run()
 
 	var vendorId gousb.ID = 0x0fcf
 	var productId gousb.ID = 0x1008
 	var deviceNumber uint32 = 3001
 
-	listenForAntDevice(vendorId, productId, deviceNumber)
-
-	fmt.Println("channel closed")
-}
-
-func main() {
-	exec.Command("hciconfig", "hci0", "down").Run()
-	exec.Command("hciconfig", "hci0", "up").Run()
-
-	ExposeBluetooth()
+	events := make(chan Event)
+	go ListenForTrainer(vendorId, productId, deviceNumber, events)
+	ExposeBluetooth(events)
 }