Guide to using StartTX

[leearmstrong]

Amazing wrapper! Love that you've done this.

I am confused on how to "feed" the StartTX with a constant stream of data. Is there an example anywhere at all?

Thanks!

[SarahRoseLives]

How it works:

StartTX takes a callback that continuously fills its buffer with IQ (in-phase/quadrature) samples.

The callback is called repeatedly as HackRF needs more data for transmission.

You can replace the random pattern with any waveform, such as a sine wave, a constant signal, etc

This is the minimal example for feeding HackRF StartTX with a continuous stream.
Replace the buffer fill code with your own signal as needed!

package main

import (
	"log"
	"math/rand"
	"time"

	"github.com/samuel/go-hackrf/hackrf"
)

func main() {
	// Initialize HackRF driver and open device
	if err := hackrf.Init(); err != nil {
		log.Fatalf("hackrf.Init() failed: %v", err)
	}
	defer hackrf.Exit()

	dev, err := hackrf.Open()
	if err != nil {
		log.Fatalf("hackrf.Open() failed: %v", err)
	}
	defer dev.Close()

	// Set desired transmit parameters (example: 440 MHz, 10 MHz sample rate, gain 40)
	if err := dev.SetFreq(440_000_000); err != nil {
		log.Fatalf("SetFreq failed: %v", err)
	}
	if err := dev.SetSampleRate(10_000_000); err != nil {
		log.Fatalf("SetSampleRate failed: %v", err)
	}
	if err := dev.SetTXVGAGain(40); err != nil {
		log.Fatalf("SetTXVGAGain failed: %v", err)
	}
	if err := dev.SetAmpEnable(true); err != nil {
		log.Fatalf("SetAmpEnable failed: %v", err)
	}

	log.Println("Starting HackRF transmission of a constant stream...")

	// StartTX expects a callback function that fills buf with IQ samples continuously.
	// buf is filled with int8 values, interleaved as I,Q,I,Q,...
	// This example fills buf with random IQ values as a dummy constant stream.
	err = dev.StartTX(func(buf []byte) error {
		// Fill the buffer with a test pattern, e.g., a constant signal, noise, or waveform
		for i := 0; i < len(buf); i += 2 {
			buf[i] = int8(rand.Intn(256) - 128)     // I sample: random noise
			buf[i+1] = int8(rand.Intn(256) - 128)   // Q sample: random noise
		}
		// If you want a constant tone, you could fill with a fixed value instead.
		// Example for constant carrier:
		// for i := 0; i < len(buf); i += 2 {
		//     buf[i] = 64    // I sample: constant amplitude
		//     buf[i+1] = 0   // Q sample: zero
		// }
		return nil
	})
	if err != nil {
		log.Fatalf("StartTX failed: %v", err)
	}

	log.Println("HackRF transmission is live. Press Ctrl+C to stop.")
	for {
		time.Sleep(time.Second)
	}
}