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62 lines
1.5 KiB
Go
62 lines
1.5 KiB
Go
package main
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import (
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"math/rand"
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"time"
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"tinygo.org/x/bluetooth"
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)
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var adapter = bluetooth.DefaultAdapter
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// TODO: use atomics to access this value.
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var heartRate uint8 = 75 // 75bpm
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func main() {
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println("starting")
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must("enable BLE stack", adapter.Enable())
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adv := adapter.DefaultAdvertisement()
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must("config adv", adv.Configure(bluetooth.AdvertisementOptions{
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LocalName: "Go HRS",
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ServiceUUIDs: []bluetooth.UUID{bluetooth.ServiceUUIDHeartRate},
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}))
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must("start adv", adv.Start())
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var heartRateMeasurement bluetooth.Characteristic
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must("add service", adapter.AddService(&bluetooth.Service{
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UUID: bluetooth.ServiceUUIDHeartRate,
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Characteristics: []bluetooth.CharacteristicConfig{
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{
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Handle: &heartRateMeasurement,
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UUID: bluetooth.CharacteristicUUIDHeartRateMeasurement,
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Value: []byte{0, heartRate},
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Flags: bluetooth.CharacteristicNotifyPermission,
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},
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},
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}))
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nextBeat := time.Now()
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for {
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nextBeat = nextBeat.Add(time.Minute / time.Duration(heartRate))
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println("tick", time.Now().Format("04:05.000"))
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time.Sleep(nextBeat.Sub(time.Now()))
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// random variation in heartrate
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heartRate = randomInt(65, 85)
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// and push the next notification
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heartRateMeasurement.Write([]byte{0, heartRate})
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}
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}
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func must(action string, err error) {
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if err != nil {
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panic("failed to " + action + ": " + err.Error())
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}
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}
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// Returns an int >= min, < max
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func randomInt(min, max int) uint8 {
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return uint8(min + rand.Intn(max-min))
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}
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