Comments (5)
The GPS module has a ferrite ( PZ2012D800-3R0TF) in series for filtering.
If I remember well an inductance in series is good to filter out high frequency noise, the lower frequency it start to be effective filtering depends on hysteresis characteristic, and inductance value AFAIR, do we have more info about that inductance so we could at least guess what frequencies of conducted noise should get filtered?
from board.
Check if the power fluctuates with an oscilloscope. Maybe it just needs a decoupling capacitor.
from board.
Check if the power fluctuates with an oscilloscope. Maybe it just needs a decoupling capacitor.
Thanks @CodeFetch for the sugestion. I already mesured, DC power is good, and the GPS board already has a DC decoupling capacitor and also a ferrite bead in series but it seems it is not enaugh.
from board.
The culprit of this issue is that the PCIe is generating the interference. The power sources are not the problem as we bypassed them and the problem persisted. When we disable PCIe directly from the registers of the SoC then the problem dissapears. Also the noise is not present when the board is booting until the PCIe root complex starts. We did some measurements of the noise with a b200 USRP and the noise is in a wide range of the spectrum.
We are working at #54 improving the impedance of the PCIe lines in the mega board with some hope.
from board.
Some time ago I was told by an electronics engineer that the PCIe lines are far too long and should not move along the whole board. He said even with shielding it would unlikely pass CE conformity tests. I'll kindly ask him to have a look for a solution.
from board.
Related Issues (20)
- Move PCIe1 device HOT 1
- Change PCIe1 3.3V source HOT 2
- Change GPS 3.3V source HOT 1
- Individual disable for PCIe0 and 1 HOT 1
- Add hack ethernet port HOT 1
- Add magnetics board option HOT 1
- Power domain isolation HOT 2
- Shorten GPS uart path HOT 1
- Add JTAG connector HOT 1
- General track and vias review
- Complete BOM HOT 7
- Improve impedance of PCIe routing HOT 4
- Remove SPI connection from watchdog to core board (introduced by mistake in the Eagle to Kicad migration) HOT 1
- Improve Ethernet differential pair impedance and reduce series resistance HOT 2
- Missing holes in PCB HOT 6
- Missing Core Board? HOT 2
- Properly design coupled transmission lines HOT 2
- Add a way to disconnect the power to the board through GPIO HOT 3
- General Silk screen check
- Change JATG pull down resistors Value
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from board.