forked from myriadrf/limedrv
/
fftaverage.go
204 lines (167 loc) · 4.11 KB
/
fftaverage.go
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package main
import (
"fmt"
"github.com/funcube-dev/limedrv"
"github.com/racerxdl/segdsp/dsp"
"github.com/racerxdl/segdsp/dsp/fft"
"github.com/racerxdl/segdsp/tools"
"image"
"image/color"
"image/jpeg"
"log"
"math"
"os"
"sync"
"time"
)
const centerFreq = 90e6
const sampleRate = 20e6
const overSample = 2
const fftChunkSize = 16384
const numAverage = 64
var finishedWork chan bool
var dev *limedrv.LMSDevice
var samplesBuffer = make([][]complex64, numAverage)
var currentBuff = 0
var writeLock = sync.Mutex{}
func OnSamples(data []complex64, _ int, _ uint64) {
writeLock.Lock()
defer writeLock.Unlock()
if currentBuff >= numAverage {
return
}
samplesBuffer[currentBuff] = data[:fftChunkSize]
currentBuff++
if currentBuff == numAverage {
finishedWork <- true
}
}
func combine(c1, c2 color.Color) color.Color {
r, g, b, a := c1.RGBA()
r2, g2, b2, a2 := c2.RGBA()
return color.RGBA{
R: uint8((r + r2) >> 9), // div by 2 followed by ">> 8" is ">> 9"
G: uint8((g + g2) >> 9),
B: uint8((b + b2) >> 9),
A: uint8((a + a2) >> 9),
}
}
func DrawLine(x0, y0, x1, y1 float32, color color.Color, img *image.RGBA) {
// DDA
_, _, _, a := color.RGBA()
needsCombine := a != 255 && a != 0
var dx = x1 - x0
var dy = y1 - y0
var steps float32
if tools.Abs(dx) > tools.Abs(dy) {
steps = tools.Abs(dx)
} else {
steps = tools.Abs(dy)
}
var xinc = dx / steps
var yinc = dy / steps
var x = x0
var y = y0
for i := 0; i < int(steps); i++ {
if needsCombine {
var p = img.At(int(x), int(y))
img.Set(int(x), int(y), combine(p, color))
} else {
img.Set(int(x), int(y), color)
}
x = x + xinc
y = y + yinc
}
}
func main() {
devices := limedrv.GetDevices()
finishedWork = make(chan bool)
log.Printf("Found %d devices.\n", len(devices))
if len(devices) == 0 {
log.Println("No devices found.")
os.Exit(1)
}
if len(devices) > 1 {
log.Println("More than one device found. Selecting first one.")
}
var di = devices[0]
log.Printf("Opening device %s\n", di.DeviceName)
dev = limedrv.Open(di)
log.Println("Opened!")
window := dsp.BlackmanHarris(fftChunkSize, 61)
var ch = dev.RXChannels[limedrv.ChannelA]
dev.SetSampleRate(sampleRate, overSample)
ch.Enable().
SetAntennaByName("LNAW").
SetGainNormalized(0.5).
SetLPF(sampleRate).
EnableLPF().
SetCenterFrequency(centerFreq)
dev.SetCallback(OnSamples)
dev.Start()
log.Println("Waiting for work finish")
<- finishedWork
dev.Stop()
dev.Close()
log.Printf("Computing FFT\n")
var fftDb = make([]float32, fftChunkSize)
var fftMax = float32(-999999999)
var fftMin = float32(9999999999)
for _, v := range samplesBuffer {
for j := 0; j < fftChunkSize; j++ {
// Apply window to FFT
var s = v[j]
var r = real(s) * float32(window[j])
var i = imag(s) * float32(window[j])
v[j] = complex(r, i)
}
// Calculate FFT
f := fft.FFT(v)
for i := 0; i < len(f); i++ {
// Convert FFT to Power in dB
var v = tools.ComplexAbsSquared(f[i]) * (1.0 / sampleRate)
v = float32(10 * math.Log10(float64(v)))
fftDb[i] += v
}
}
// Compute Average
for i := range fftDb {
fftDb[i] /= numAverage
if fftDb[i] > fftMax {
fftMax = fftDb[i]
} else if fftDb[i] < fftMin {
fftMin = fftDb[i]
}
}
// Compute delta to make FFT always fit in the image
var fftDelta = fftMax - fftMin
log.Printf("Drawing FFT %dx%d\n", len(fftDb), 1024)
img := image.NewRGBA(image.Rect(0, 0, len(fftDb), 1024))
var size = img.Bounds()
var lastX = float32(0)
var lastY = float32(0)
for i := 0; i < len(fftDb); i++ {
var iPos = (i + len(fftDb)/2) % len(fftDb)
var s = float32(fftDb[iPos])
var v = (float32(fftMax) - s) * (float32(size.Dy()) / float32(fftDelta))
var x = float32(i)
if i != 0 {
DrawLine(lastX, lastY, x, v, color.NRGBA{R: 0, G: 127, B: 127, A: 255}, img)
}
lastX = x
lastY = v
}
log.Println("Saving file")
// Encode as JPEG and Save
filename := fmt.Sprintf("%d-%.0f-%.0f-fft.jpg", time.Now().Unix(), centerFreq, sampleRate)
f, err := os.Create(filename)
defer f.Close()
if err != nil {
panic(err)
}
err = jpeg.Encode(f, img, nil)
if err != nil {
panic(err)
}
log.Printf("File saved at %s\n", filename)
}