ADALM-PLUTO dual-port mod: Can't use DDS on both Tx Ports in Python

Question

I've been trying to use the DDS to set up two CW outputs on the ADALM-PLUTO (modified for 2 tx and 2 rx ports). 
 I've been finding that only the second output to be declared will output a tone. Is this a limitation of the firmware, or am I missing something? 
 That is, if I use 
 sdr.dds_single_tone(freq, scale, 0) 
 ...followed by 
 sdr.dds_single_tone(freq, scale, 1) 
 
 ...there will only be a tone at the second port. 
 But if I switch the order of the lines, there will only be a tone at the first port. Is there something more I need to do? 
 Here's a script that illustrates my issue (if you loop the Tx back to the Rx ports) 
 import adi
import numpy as np
import matplotlib.pyplot as plt

sdr = adi.ad9361("ip:192.168.2.1")

sdr.rx_enabled_channels = [0, 1]
sdr.tx_enabled_channels = [0, 1]

sample_rate = int(30.72e6)
lo_freq = int(1e9)
cw_freq = int(1e6)

sdr.sample_rate = sample_rate
sdr.rx_rf_bandwidth = sample_rate
sdr.tx_rf_bandwidth = sample_rate

# set up Tx
sdr.tx_lo = lo_freq

sdr.tx_hardwaregain_chan0 = -10
sdr.tx_hardwaregain_chan1 = -10

## Only the second DDS tone will generate an output ##
######################################################
sdr.dds_single_tone(cw_freq, 0.9, channel=0)
sdr.dds_single_tone(0 - cw_freq, 0.9, channel=1)
######################################################

# set up Rx
sdr.rx_lo = lo_freq
sdr.gain_control_mode_chan0 = 'manual'
sdr.gain_control_mode_chan1 = 'manual'
sdr.rx_hardwaregain_chan0 = 0
sdr.rx_hardwaregain_chan1 = 0

# Clear Buffer
for i in range (0, 10):
 sdr.rx()

# Receive samples
rx_samples = sdr.rx()


# Calculate Power Spectral Density (Frequency Domain)
psd_1 = np.abs(np.fft.fftshift(np.fft.fft(rx_samples[0])))**2
psd_dB_1 = 10*np.log10(psd_1)
psd_2 = np.abs(np.fft.fftshift(np.fft.fft(rx_samples[1])))**2
psd_dB_2 = 10*np.log10(psd_2)

# generate frequency span
f = np.linspace(sample_rate/-2, sample_rate/2, sdr.rx_buffer_size)
f += sdr.rx_lo

# Plot
full_fig = plt.figure(0)
time_plot = full_fig.add_subplot(211)
freq_plot = full_fig.add_subplot(212)

# Time Plot
time_plot.plot(np.real(rx_samples[0][:100]), label='Rx 1 Real')
time_plot.plot(np.imag(rx_samples[0][:100]), label='Rx 1 Imag')
time_plot.plot(np.real(rx_samples[1][:100]), label='Rx 2 Real')
time_plot.plot(np.imag(rx_samples[1][:100]), label='Rx 2 Imag')

time_plot.set_xlabel("Samples")
time_plot.legend()
time_plot.grid()

# Freq Plot
freq_plot.plot(f/1e6, psd_dB_1, alpha=0.7, label='Rx 1')
freq_plot.plot(f/1e6, psd_dB_2, alpha=0.7, label='Rx 2')
freq_plot.legend()

freq_plot.set_xlabel("Frequency [MHz]")
freq_plot.set_ylabel("PSD")
freq_plot.grid()

plt.show()

vs.

Alexandra · Accepted Answer

Hi, You can replace the 2 sdr.dds_single_tone calls with something similar to the following: #### [TX1_I_F1, TX1_I_F2, TX1_Q_F1, TX1_Q_F2, TX2_I_F1, TX2_I_F2, TX2_Q_F1, TX2_Q_F2]
sdr.dds_frequencies = [cw_freq, 0, cw_freq, 0, cw_freq, 0, cw_freq, 0]
sdr.dds_scales = [0.9, 0, 0.9, 0, 0.9, 0, 0.9, 0]
#sdr.dds_phases = []
sdr.dds_enabled = [1, 1, 1, 1, 1, 1, 1, 1]
 You need to change the values to match what you need for scale, frequency and phase values. The "dds_single_tone" function generates the tone on the required channel but resets all the values that were previously setup for other channels. The way described above should allow for more flexibility in generating what you need. The config lists have 8 elements due to both TX channels being dual tone. In order to mute the DDS at startup you need to set the scale to 0. Additionally, at the end of the script you could use sdr.disable_dds() to ensure all get disabled. -Alexandra)

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ADALM-PLUTO dual-port mod: Can't use DDS on both Tx Ports in Python