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SP9BSL
positron
alter Hase
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Re:VisAir ddc modul und DSP PCBs Rolin
« Reply #76 on: 13. March 2020, 19:43:35 »
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Andy,
Slawek not Artur, luckily SP9 is far from SP3 
You must have the main clock 122.88MHz from ADC to FPGA but first the ADC must have it from TCXO. The frequent problem is that ADC has differential clock input and the signal is not proper on both inputs the negative and positive, what exact type of TCXO you have?
I see your oscilloscope has 100MHz bandwidth, this is enough to see the 122.88MHz sine wave with lower peak voltage. Check the pins CLKM, CLKP (7th,8th) of ADC and then pin 60 of FPGA (same as the 26th at ADC).
At the MCLK there must be 12.288MHz (256*fs).
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| « Last Edit: 13. March 2020, 19:52:00 by SP9BSL » |
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73 Slawek
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BO_Andy
Urgestein
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Ich bin schon Groß und kann Alleine Laufen
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Re:VisAir ddc modul und DSP PCBs Rolin
« Reply #77 on: 13. March 2020, 21:20:01 »
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slawek I have the TCXO VG-4513CA order number SER3906CT-ND
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SP9BSL
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alter Hase
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Re:VisAir ddc modul und DSP PCBs Rolin
« Reply #78 on: 13. March 2020, 21:40:52 »
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You have the correct VCXO with LVPECL outputs. The peak to peak voltage of clock is about 800mV with 2V DC. You should have the 122.88 MHz on both inputs of ADC (pins 7 & 8 negated) and at the ADC output (pin 26), same on 60th pin of FPGA.
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73 Slawek
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BO_Andy
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Re:VisAir ddc modul und DSP PCBs Rolin
« Reply #79 on: 14. March 2020, 09:22:09 »
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slawek the TCXO swings wrong for some reason he delivers garbage
Lg BO_Andy
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SP9BSL
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alter Hase
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Re:VisAir ddc modul und DSP PCBs Rolin
« Reply #80 on: 14. March 2020, 09:32:34 »
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Andy, according to datasheet your VCXO has OE active high (pin 2) check the voltage on it and if is not 3.3V try pull up it. I see the board has this pin floating.
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73 Slawek
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BO_Andy
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Ich bin schon Groß und kann Alleine Laufen
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Re:VisAir ddc modul und DSP PCBs Rolin
« Reply #81 on: 14. March 2020, 18:29:28 »
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very interesting the pin really hangs in the air according to the layout anyway ma can measure 3.3v there
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