Channel Alignment Failure

tony.bigbee · 30 May 2018 06:43

Hello @IgnasJ – I’m seeing “Channel alignment failed” at least 1 out every 10 times I run a program, from a cold start, that streams 2 RX channels-but with no apparent pattern. I’m using the master branch release 18.04.1 and powering the device via USB 3 from a laptop. Once this warning occurs, it occurs on all successive runs until the LimeSDR is restarted.

I see that this comes from the Streamer::AlignRxTSP function. What is the root cause of the problem / why does it appear randomly?

github.com

myriadrf/LimeSuite/blob/5caf4ce34d3b9e4d74170930416672bb4526ac34/src/protocols/Streamer.cpp#L335


dataPort->WriteRegister(0x0007, 3);


dataWr[0] = (1 << 31) | (uint32_t(0x0020) << 16) | 0x55FE;
dataWr[1] = (1 << 31) | (uint32_t(0x0020) << 16) | 0xFFFD;


for (int i = 0; i < 100; i++)
{
    dataPort->WriteLMS7002MSPI(&dataWr[0], 2, chipId);
    dataPort->ResetStreamBuffers();
    fpga->StartStreaming();
    if (dataPort->ReceiveData((char*)buf, sizeof(FPGA_DataPacket), chipId, 50) != sizeof(FPGA_DataPacket))
    {
        lime::warning("Channel alignment failed");
        break;
    }
    fpga->StopStreaming();
    dataPort->AbortReading(chipId);
    if (buf[4] == buf[5])
        break;
}
delete[] buf;

Thanks.

IgnasJ · 31 May 2018 19:32

“Channel alignment failed” warning means that channel phases/time offset may not be correctly aligned. Channel alignment is not guaranteed to work every time so the message may appear sometimes. However the warning should not come from Streamer::AlignRxTSP(). If it does, then something is really wrong as it means that software is unable to receive samples from the board. Do you still get sample stream after getting the warning?

tony.bigbee · 3 June 2018 04:40

Thanks – The sample stream appears to work fine when I receive this message. I noticed that the message may also be emitted by Streamer::AlignRxRF; do you conclude that this function is emitting the message since streaming works?

Why is channel alignment not guaranteed to work every time?