TX streaming fails with version 18.06

The latest version of LimeSuite + FPGA GW + FX3 FW doesn't work for me in TX (RX works perfectly). For easy testing, I'm using the following Python script that uses SoapySDR to send samples to the LimeSDR-USB for TX.

#!/usr/bin/env python2

import SoapySDR
from SoapySDR import * #SOAPY_SDR_ constants
import numpy as np

sdr = SoapySDR.Device()

#apply settings
sdr.setSampleRate(SOAPY_SDR_TX, 0, 1e6)
sdr.setFrequency(SOAPY_SDR_TX, 0, 434e6)
sdr.setAntenna(SOAPY_SDR_TX, 0, 'BAND1')

#setup a stream (complex floats)
txStream = sdr.setupStream(SOAPY_SDR_TX, SOAPY_SDR_CF32, [0])
sdr.activateStream(txStream) #start streaming

#create a re-usable buffer for rx samples
N = 2**18
N = 1024
buff = np.zeros(N, dtype=np.complex64)
while True:
    sr = sdr.writeStream(txStream, [buff], N)
    print sr

The script starts running fine and we get

ret=1024, flags=0, timeNs=0

but after a very small time we start getting

ret=-1, flags=0, timeNs=0

for all calls to writeStream().

Other SDR softwares fail as well. For instance, when using GNU Radio through gr-osmosdr or through gr-limesdr, the LimeSDR sink quickly blocks and doesn't accept any new samples.

Testing combinations of older versions of LimeSuite, the FPGA GW and the FX3 FW I have determined the culprit to be version 18.06 of the FPGA GW (LimeSDR-USB_HW_1.4_r2.15.rbf). When downgrading the FPGA GW and FX3 FW to version 18.03, everything works fine, even with the master branch of LimeSuite. Also, everything works fine if I mix FPGA GW version 18.03 with FX3 FW version 18.06. I guess that the problem must be in FPGA GW version 18.06.

myriadrf / LimeSDR-USB_GW

TX streaming fails with version 18.06 #4