59 lines
1.5 KiB
Go
59 lines
1.5 KiB
Go
package main
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import (
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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.New16BitUUID(0x2A37)},
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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.New16BitUUID(0x180D), // Heart Rate
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Characteristics: []bluetooth.CharacteristicConfig{
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{
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Handle: &heartRateMeasurement,
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UUID: bluetooth.New16BitUUID(0x2A37), // Heart Rate Measurement
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Value: []byte{0, heartRate},
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Flags: bluetooth.CharacteristicReadPermission | bluetooth.CharacteristicWritePermission,
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WriteEvent: func(client bluetooth.Connection, offset int, value []byte) {
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if offset != 0 || len(value) < 2 {
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return
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}
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if value[1] != 0 { // avoid divide by zero
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heartRate = value[1]
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println("heart rate is now:", heartRate)
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}
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},
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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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}
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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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