Random notes for operating DBBC in the field
VSI connectors and data flow (Gino, email 20.01.2011)
What is received by the second Core2 in the 'vsi1' position is shifted by the second Core2 into the
'vsi2' place -- thus the output of the second Core2 will be {vsi1out:own data, vsi2out:previous board}
Clock phase calibration on the Polyphase firmware
A test tone at 764 MHz is injected to input 1 of all IF boards. Calibration is run with 'C' in the test_poly16 control program. Prior to calibration, use 'p' to list the total powers of all channels and verify that channel#8 has maximum power while other channels have near zero power. After calibration (~5 minutes) a list of detected optimal phase values for each of the boards is printed. These values can be applied with "f=<boardNr>,<phaseValue>". They should be entered into the C:\dbbc_conf\*.txt file as well.
Note that after 'C' completes all boards remain set to the last tested phase (255 255 255 255). You should use manual "f=..." or restart test_poly16 to apply more proper values immediately after the 'C' run.
Clock phase calibration on the Tunable firmware (Gino, email 20.01.2011)
"There is a dbbc_config_file.txt with calibration setting. Here is reported. The goal of this calibration is to find the best phase relation between data and clock in the internal FPGA capture point. To do so a tone at an almost central frequency in the second Nyquist zone is injected and the 4 bbcs present in one Core2 are tuned equispaced in the entire band widh respect to this central tone. No bbc is tuned to see the tone. When things are correct the tone should not produce a contribution to the total power detected in all the 8 basebands 16 MHz wide (4U+4L). Indeed when phases are not correct spurious and additional components are generated and are visible in the bbcs' bands producing a total power contribution. Hope this could clarify the procedure."
Clock phases can be set manually with "f=<boardNr>,<phaseValue>". One channel may be viewed on the Analog Monitor output with "m=<boardNr>,<channelNr>" or "mon=<boardNr>,<channelNr>".
Modifying the phase of a board higher up in the stack will affect the spectrum of a monitor signal copied from farther down from the stack: Changing the phase in the Nth Core2 will change the phase relation you use to capture data from the monitor bus, with such consequences. Calibration is taking care of information produced and 'resident' only in the board under analysis, the total power. A more clever calibration process is anyway probably necessary.
