Pull IQ Samples To Make Constellation Plot (API)

I’m trying to pull out raw IQ samples to create a constellation plot using the API. When I use spike I get a nice QPSK signal constellation, but I’m having trouble getting anything similar with the API.

I’m using the example that comes with the SDK, all I’ve done is change some frequency/bandwidth values.

My carrier is 1.84MHz wide at 70MHz. The documentation says that IQ samples are interleaved and range from +/-1. I’m assuming this means that the resulting array is structured like:
I1, Q1, I2, Q2, I3, Q3…etc

My problem is that I’m getting IQ values that range from +/- 0.01, so I think I’m just seeing noise. If I plot I and Q separately they seem like roughly ok sine waves. Also if I plot IQ in 2D to make a constellation, I just get a big circular donut, nothing that looks like there are 4 converging points.

I use the reference level of -40 because that worked in Spike.

Anyone know what I’m missing? Any helps is appreciated

I’ve adjusted the demo code to take the samples and dump them to a file:

int id = -1;
            bbStatus status = bbStatus.bbNoError;

            txtResults.Text += "Opening Device, Please Wait\n";
            status = bb_api.bbOpenDevice(ref id);
            if (status != bbStatus.bbNoError)
            {
                txtResults.Text += "Error: Unable to open BB60\n";
                txtResults.Text += bb_api.bbGetStatusString(status) + "\n";
                return;
            }
            else
            {
                txtResults.Text += "Device Found\n\n";
            }

            Console.Write("Configuring the device to stream I/Q data\n");
            bb_api.bbConfigureCenterSpan(id, 70000000, 4.0e6); //center hz, span hz
            bb_api.bbConfigureLevel(id, -40.0, bb_api.BB_AUTO_ATTEN);
            bb_api.bbConfigureGain(id, bb_api.BB_AUTO_GAIN);
            bb_api.bbConfigureIQ(id, bb_api.BB_MIN_DECIMATION, 4.0e6); //bandwidth hz

            status = bb_api.bbInitiate(id, bb_api.BB_STREAMING, bb_api.BB_STREAM_IQ);
            if (status != bbStatus.bbNoError)
            {
                txtResults.Text += "Error: Unable to initialize BB60 for streaming\n";
                txtResults.Text += bb_api.bbGetStatusString(status) + "\n";
                return;
            }

            int return_len = 0;
            int samples_per_sec = 0;
            double bandwidth = 0.0;
            bb_api.bbQueryStreamInfo(id, ref return_len, ref bandwidth, ref samples_per_sec);
            txtResults.Text += "Initialized Stream for \n";
            txtResults.Text += "Samples per second: " + (samples_per_sec / 1.0e6).ToString() + " MS/s\n";
            txtResults.Text += "Bandwidth: " + (bandwidth / 1.0e6).ToString() + " MHz\n";
            txtResults.Text += "Samples per function call: " + return_len.ToString() + "\n";

            // Alternating I/Q samples
            // return_len is the number of I/Q pairs, so.. allocate twice as many floats
            float[] iq_samples = new float[return_len * 2];
            int[] triggers = new int[80];

            bb_api.bbFetchRaw(id, iq_samples, triggers);
            txtResults.Text += "Retrieved one I/Q packet\n\n";

            StringBuilder sb = new StringBuilder();

            foreach(float sample in iq_samples)
            {
                sb.Append(sample.ToString() + Environment.NewLine);
            }

            File.WriteAllText("output.csv", sb.ToString());

            txtResults.Text += "Closing Device\n";
            bb_api.bbCloseDevice(id);