62 lines
1.3 KiB
Go
62 lines
1.3 KiB
Go
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package main
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import (
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"fmt"
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"math"
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"os"
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"strconv"
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"strings"
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"time"
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)
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// adc is an abstract ADC-based analog input.
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type adc interface {
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// Read returns the ADC value in volts.
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Read() (float32, error)
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}
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// bbADC implements adc using a BeagleBone's built-in ADC.
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type bbADC struct {
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path string
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}
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// newBBADC returns a BeagleBone ADC for a given channel number.
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func newBBADC(num int) (*bbADC, error) {
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path := fmt.Sprintf("/sys/bus/iio/devices/iio:device0/in_voltage%d_raw", num)
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if _, err := os.Stat(path); err != nil {
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return nil, fmt.Errorf("could not access: %w", err)
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}
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return &bbADC{
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path: path,
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}, nil
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}
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func (b *bbADC) Read() (float32, error) {
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by, err := os.ReadFile(b.path)
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if err != nil {
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return 0, err
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}
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d := strings.TrimSpace(string(by))
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v, err := strconv.ParseUint(d, 10, 64)
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if err != nil {
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return 0, err
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}
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// The ADC Vref/Vdd is at 1.8V and is 10-bit (0-4095).
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vadc := float32(v) * 1.8 / 4096.0
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// The ADC is connected through a resistor divider.
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r1 := float32(1000.0)
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r2 := float32(4698.0)
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vin := vadc / (r1 / (r1 + r2))
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return vin, nil
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}
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// fakeADC implements an adc that outputs a sine wave. This is used for testing.
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type fakeADC struct {
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}
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func (b *fakeADC) Read() (float32, error) {
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t := float64(time.Now().UnixMilli()) / 1000
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v := (math.Sin(t/10)+1)*(6.5/2) + 2
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return float32(v), nil
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}
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