Hi, I have a CWLITE-ARM and a CWLITE-NANO. I am trying to see if I could use one of those to collect traces on an FPGA. I notice that the capture card PCB is identical to the one used on the CWLITE-ARM. Would I be able to then just break that PCB and wire up the 3 measure lines to my own FPGA to collect traces? or is there something else I would need?
I would like to just buy the UFO baseboard + capture card + FPGA daughterboard but I don’t think I can get all that paid for just now. So seeing what I can do with the HW I already have. Thank you!
Yup, the CWLite Arm board is just the Lite capture board with an Arm target attached. If you break the target section off, and solder the 20-pin connectors and SMA connectors on, you’ve got a Lite capture board.
If you’re using the CW308, you should connect both the measure port and 20-pin connector. If you’re using a non-CW target board, you’ll need to modify the target similar to how the LPC was modified in https://wiki.newae.com/Tutorial_A9_Bypassing_LPC1114_Read_Protect.
Let me know if you have more questions or want me to go more in depth with anything here.
Alex
Hi Alex, thank you for that info! So I would need to connect the wires from the 20-pin connector as well as the SMA connector to my FPGA target?
Would I also have to modify the FPGA like the LPC example you showed? I am just programming the FPGA with a netlist as normal and would likely just need to provide a trigger for computation to start via the CWLITE board.
Really, I’m just trying to use the CWLITE as an oscilloscope here. I have a small amount of hardware running on an FPGA and I need to collect some traces of it to run TVLA. I’m not if there is a more straightforward way of doing it than what I am thinking of doing. Any thoughts you might have would be most appreciated.
Thank you!
Hi,
You’ll need some way to measure the current going into the FPGA. For our CW targets, we do this via a shunt resistor - basically, we measure the high frequency voltage drop across the resistor. We also remove any decoupling capacitors on the low side of the shunt as well, as these will filter out the high frequency voltage drop. There’s other ways of measuring current that are less invasive, too.
For example, you can measure the magnetic field emitted by the FPGA (decoupling capacitors are another good option here) using an H-Field probe. We sell an H-Field probe as part of a kit: https://www.mouser.ca/ProductDetail/NewAE/NAE-PBSET-PSU-03?qs=sGAEpiMZZMve4%2FbfQkoj%2BPHOGYuApxDf6wG0JGX01iU%3D. You can also build such a probe pretty cheaply yourself, though I do recommend some additional low noise amplification. Our probe kit comes with a 20dB LNA (plus a differential probe).
Alex
Thank you. For the resistor, is that already present on the CW-LITE capture board or would I have to add one to measure across? So if i connect the appropriate wires from the 20-pin SMA connector to my FPGA that is.
The H-field probe is a good idea but the circuit I am running is very small <1k gates so I worry it will be too small to be picked up. I’ve seen that mentioned elsewhere which is why I’ve stuck to just measuring power for now.
You’ll need to make the modification on the board, as close to the power pins of the FPGA as possible. You also need to remove the decoupling caps for the FPGA.
Alex