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Message ID: 2107     Entry time: Mon Jul 23 16:44:59 2018
Author: johannes 
Type: Notes 
Category: DAQ 
Subject: Red Pitaya PSA 

Since one of the two Red Pitayas is currently consumed for transfer function measurements (RP1, IP:, used primarily by cryocavs), I added v2 of the phasemeter core, which had been running on RP1 for an eternity, to the other one (RP2, IP:, used by SiFi). Both cores are located in /opt/redpitaya/ (local directory on RP2)


The v2 core is now loaded by default on reboot. The default behavior is controlled by the corresponding lines in /opt/redpitaya/sbin/discovery.sh

# cat /opt/redpitaya/rp_pm_fpga-core.bit > /dev/xdevcfg
cat /opt/redpitaya/rp_pm_fpga-core_v2.bit > /dev/xdevcfg

# /opt/redpitaya/bin/rp_pm_tcp-server &
/opt/redpitaya/bin/rp_pm_tcp-server_v2 &

Each core requires the matching client GUI to connect from the workstation. On both Gaston and Spirou these can be launched by executing

python3 /home/controls/utils/redpitaya/clientGUI/v1/rp_pm_remote_gui.py
python3 /home/controls/utils/redpitaya/clientGUI/v2/rp_pm_remote_gui.py


Difference between v1 and v2

The data transfer rate to the remote host computer has been increased from 200 kHz (v1) to 500 kHz (v2), in exchange for removing the second phasemeter channel completely, which is not used for beat measurements. The downsampling strategy is also different between the versions:

  • v1 has a 6-stage CIC filter that downsamples 125 MHz to 200 kHz.
  • v2 has a 6-stage CIC filter that downsamples 125 MHz to 1 MHz, and then uses a steep FIR filter as the last step to normalize the pass-band of the FIR filter with subsequent downsampling to 500 kHz

The v2 client GUI has an indicator for the amplitude of the signal instead of the frequency indicator for the second channel. All plot controls behave identically.

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