examples: add example that makes connections to multiple peripherals

examples/multiples/main.go

@@ -0,0 +1,146 @@
+// This example scans and then connects to multiple Bluetooth peripherals
+// that provide the Heart Rate Service (HRS).
+//
+// Once connected to all the desired devices, it subscribes to notifications.
+//
+// To run on bare metal microcontroller:
+// tinygo flash -target metro-m4-airlift -ldflags="-X main.Devices=D9:2A:A1:5C:ED:56,4D:A1:3C:24:F0:46" -monitor ./examples/multiples/
+//
+// To run on OS:
+// go run ./examples/multiples/ D9:2A:A1:5C:ED:56,64:0B:1D:46:D8:1D
+package main
+
+import (
+	"context"
+	"os"
+	"slices"
+	"time"
+
+	"tinygo.org/x/bluetooth"
+)
+
+var (
+	adapter = bluetooth.DefaultAdapter
+
+	heartRateServiceUUID        = bluetooth.ServiceUUIDHeartRate
+	heartRateCharacteristicUUID = bluetooth.CharacteristicUUIDHeartRateMeasurement
+
+	exitCtx context.Context
+)
+
+func main() {
+	exitCtx = initExitHandler()
+
+	println("enabling")
+
+	// Enable BLE interface.
+	must("enable BLE stack", adapter.Enable())
+
+	scanResults := make(map[string]bluetooth.ScanResult)
+	finished := make(chan bool, 1)
+
+	searchList, _ := connectAddresses()
+
+	// Start scanning.
+	println("scanning...")
+	err := adapter.Scan(func(adapter *bluetooth.Adapter, result bluetooth.ScanResult) {
+		print(".")
+		// is the scanned device one of the ones we want?
+		if slices.Contains(searchList, result.Address.String()) {
+			if _, ok := scanResults[result.Address.String()]; !ok {
+				println(".")
+				println("found device:", result.Address.String(), result.RSSI, result.LocalName())
+				scanResults[result.Address.String()] = result
+			}
+
+			if len(scanResults) == len(searchList) {
+				println("All found.")
+				adapter.StopScan()
+				finished <- true
+			}
+		}
+		select {
+		case <-exitCtx.Done():
+			println("exiting.")
+			os.Exit(0)
+		default:
+		}
+	})
+	must("scan", err)
+
+	devices := []bluetooth.Device{}
+	select {
+	case <-time.After(5 * time.Second):
+		failMessage("timed out")
+		return
+	case <-exitCtx.Done():
+		println("exiting.")
+		return
+	case <-finished:
+	}
+
+	defer func() {
+		for _, device := range devices {
+			device.Disconnect()
+		}
+	}()
+
+	// now connect to all devices
+	for _, result := range scanResults {
+		device, err := adapter.Connect(result.Address, bluetooth.ConnectionParams{})
+		if err != nil {
+			failMessage(err.Error())
+			return
+		}
+
+		println("connected to", result.Address.String())
+		devices = append(devices, device)
+	}
+
+	// get services
+	println("discovering services/characteristics")
+
+	for _, device := range devices {
+		srvcs, err := device.DiscoverServices([]bluetooth.UUID{heartRateServiceUUID})
+		must("discover services", err)
+
+		if len(srvcs) == 0 {
+			failMessage("could not find heart rate service")
+			return
+		}
+
+		srvc := srvcs[0]
+
+		println("found service", srvc.UUID().String(), "for device", device.Address.String())
+
+		chars, err := srvc.DiscoverCharacteristics([]bluetooth.UUID{heartRateCharacteristicUUID})
+		if err != nil {
+			failMessage(err.Error())
+			return
+		}
+
+		if len(chars) == 0 {
+			failMessage("could not find heart rate characteristic")
+			return
+		}
+
+		char := chars[0]
+		addr := device.Address.String()
+		println("found characteristic", char.UUID().String(), "for device", addr)
+
+		char.EnableNotifications(func(buf []byte) {
+			println(addr, "data:", uint8(buf[1]))
+		})
+	}
+
+	// wait for exit
+	<-exitCtx.Done()
+	println("exiting.")
+}
+
+func must(action string, err error) {
+	if err != nil {
+		failMessage("failed to " + action + ": " + err.Error())
+		return
+	}
+}

examples/multiples/mcu.go

@@ -0,0 +1,37 @@
+//go:build baremetal
+
+package main
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"time"
+)
+
+// Devices are the MAC addresses of the Bluetooth peripherals you want to connect to.
+// Replace this by using -ldflags="-X main.Devices='[MAC ADDRESS],[MAC ADDRESS]'"
+// where [MAC ADDRESS] is the actual MAC address of the peripheral.
+// For example:
+// tinygo flash -target nano-rp2040 -ldflags="-X main.Devices='7B:36:98:8C:41:1C,7B:36:98:8C:41:1D" ./examples/heartrate-monitor/
+var Devices string
+
+func initExitHandler() context.Context {
+	return context.Background()
+}
+
+func connectAddresses() ([]string, error) {
+	addrs := strings.Split(Devices, ",")
+	if len(addrs) == 0 {
+		return nil, errors.New("no devices specified")
+	}
+
+	return addrs, nil
+}
+
+func failMessage(msg string) {
+	for {
+		println(msg)
+		time.Sleep(1 * time.Second)
+	}
+}

examples/multiples/os.go

@@ -0,0 +1,49 @@
+//go:build !baremetal
+
+package main
+
+import (
+	"context"
+	"errors"
+	"os"
+	"os/signal"
+	"strings"
+	"syscall"
+)
+
+func initExitHandler() context.Context {
+	return contextWithSignal(context.Background())
+}
+
+// ContextWithSignal creates a context canceled when SIGINT or SIGTERM are notified
+func contextWithSignal(ctx context.Context) context.Context {
+	newCtx, cancel := context.WithCancel(ctx)
+	signals := make(chan os.Signal)
+	signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM)
+	go func() {
+		select {
+		case <-signals:
+			cancel()
+		}
+	}()
+	return newCtx
+}
+
+func connectAddresses() ([]string, error) {
+	if len(os.Args) < 2 {
+		println("usage: multiples [address],[address]")
+		os.Exit(1)
+	}
+
+	addrs := strings.Split(os.Args[1], ",")
+	if len(addrs) == 0 {
+		return nil, errors.New("no devices specified")
+	}
+
+	return addrs, nil
+}
+
+func failMessage(msg string) {
+	println(msg)
+	exitCtx.Done()
+}