From 65788a6620db75696e8cc87f7f8b27f946036837 Mon Sep 17 00:00:00 2001
From: Ian Gulliver <flamingcow@gmail.com>
Date: Sat, 24 Sep 2022 16:29:26 -0700
Subject: [PATCH] Initial commit

---
 go.mod          |  5 +++
 go.sum          |  2 ++
 hh.go           | 21 ++++++++++++
 medianfilter.go | 36 ++++++++++++++++++++
 relay.go        | 25 ++++++++++++++
 ultrasonic.go   | 87 +++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 176 insertions(+)
 create mode 100644 go.mod
 create mode 100644 go.sum
 create mode 100644 hh.go
 create mode 100644 medianfilter.go
 create mode 100644 relay.go
 create mode 100644 ultrasonic.go

diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..d5e6878
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module github.com/firestuff/hh
+
+go 1.18
+
+require github.com/stianeikeland/go-rpio/v4 v4.6.0
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..7276cad
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+github.com/stianeikeland/go-rpio/v4 v4.6.0 h1:eAJgtw3jTtvn/CqwbC82ntcS+dtzUTgo5qlZKe677EY=
+github.com/stianeikeland/go-rpio/v4 v4.6.0/go.mod h1:A3GvHxC1Om5zaId+HqB3HKqx4K/AqeckxB7qRjxMK7o=
diff --git a/hh.go b/hh.go
new file mode 100644
index 0000000..b12a6cd
--- /dev/null
+++ b/hh.go
@@ -0,0 +1,21 @@
+package main
+
+import "context"
+import "fmt"
+
+import "github.com/stianeikeland/go-rpio/v4"
+
+func main() {
+	err := rpio.Open()
+	if err != nil {
+		panic(err)
+	}
+	defer rpio.Close()
+
+	us := NewUltrasonic(context.TODO(), 6, 5)
+	mf := NewMedianFilter(us.C, 9)
+
+	for dist := range mf {
+		fmt.Printf("%f\n", dist)
+	}
+}
diff --git a/medianfilter.go b/medianfilter.go
new file mode 100644
index 0000000..04761c6
--- /dev/null
+++ b/medianfilter.go
@@ -0,0 +1,36 @@
+package main
+
+import "sort"
+
+func NewMedianFilter(in chan float64, num int) chan float64 {
+	out := make(chan float64)
+
+	go func() {
+		defer close(out)
+
+		buf := make([]float64, num, num)
+		srt := make([]float64, num, num)
+		next := 0
+
+		for {
+			v, ok := <-in
+			if !ok {
+				return
+			}
+
+			buf[next%num] = v
+			next++
+
+			if next < num {
+				continue
+			}
+
+			copy(srt, buf)
+			sort.Float64s(srt)
+
+			out <- srt[num/2+1]
+		}
+	}()
+
+	return out
+}
diff --git a/relay.go b/relay.go
new file mode 100644
index 0000000..40497b3
--- /dev/null
+++ b/relay.go
@@ -0,0 +1,25 @@
+package main
+
+import "github.com/stianeikeland/go-rpio/v4"
+
+type Relay struct {
+	pin rpio.Pin
+}
+
+func NewRelay(pin int) *Relay {
+	r := &Relay{
+		pin: rpio.Pin(pin),
+	}
+
+	r.pin.Output()
+
+	return r
+}
+
+func (r *Relay) On() {
+	r.pin.High()
+}
+
+func (r *Relay) Off() {
+	r.pin.Low()
+}
diff --git a/ultrasonic.go b/ultrasonic.go
new file mode 100644
index 0000000..1b4bf8a
--- /dev/null
+++ b/ultrasonic.go
@@ -0,0 +1,87 @@
+package main
+
+import "context"
+import "errors"
+import "time"
+
+import "github.com/stianeikeland/go-rpio/v4"
+
+type Ultrasonic struct {
+	C chan float64
+
+	trig rpio.Pin
+	echo rpio.Pin
+}
+
+var timeout = errors.New("timed out waiting for device")
+
+func NewUltrasonic(ctx context.Context, trig, echo int) *Ultrasonic {
+	us := &Ultrasonic{
+		C:    make(chan float64),
+		trig: rpio.Pin(trig),
+		echo: rpio.Pin(echo),
+	}
+
+	us.trig.Output()
+	us.trig.Low()
+
+	us.echo.Input()
+
+	go us.loop(ctx)
+
+	return us
+}
+
+func (us *Ultrasonic) loop(ctx context.Context) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+
+		default:
+			us.measure()
+		}
+	}
+}
+
+func (us *Ultrasonic) measure() {
+	deadline := time.NewTimer(200 * time.Millisecond)
+
+	us.trigger()
+
+	start := us.wait(rpio.High, deadline)
+	end := us.wait(rpio.Low, deadline)
+
+	if start.IsZero() || end.IsZero() {
+		return
+	}
+
+	duration := end.Sub(start)
+	cm := duration.Seconds() * 17150
+
+	if cm > 400 {
+		return
+	}
+
+	us.C <- cm
+}
+
+func (us *Ultrasonic) trigger() {
+	us.trig.High()
+	time.Sleep(10 * time.Microsecond)
+	us.trig.Low()
+}
+
+func (us *Ultrasonic) wait(goal rpio.State, deadline *time.Timer) time.Time {
+	for {
+		select {
+		case <-deadline.C:
+			return time.Time{}
+
+		default:
+			if us.echo.Read() == goal {
+				return time.Now()
+			}
+		}
+	}
+}