Wed., Jan. 25th

Samad gave me the new 5V supply he purchased this morning.  It is BARELY big enough (2.6A), but we can try it.  Told him next time to oversize the supply by 50% or so to make sure there is enough headroom.

Today:  I'm planning to finish debugging the new timing-sync edge-capture datapath using Darryl's output stub.  Meanwhile, hopefully Juan will also come in and tie up the loose ends in the firmware.

I took the commented code out of David & Dean's new stream_pulse_data_tsedge_56.vhd module and inspected it for errors.  It looked OK apart from a possible occasional wrong behavior on reset (which I fixed).

I went through Darryl's code and simplified it significantly before I try debugging it; getting ready to test again.

Juan came in and I gave him more detailed instructions on what needs to be done to finish up the firmware; he is working on that now.

Tested Samad's supply brick with the multimeter.  It outputs nearly 9V at 0A!  I tried putting a 100 ohm load on it, and the voltage fell to about 7.5A.  It's possible that at 2.5A it would put out close to 5V, but I didn't have a large enough 3 ohm resistor handy.  I really don't want to risk frying the real FEDM board by applying too much voltage to it; the output of this supply is apparently not regulated. We are there going to need a voltage regulator board to do this properly if we're going to use this supply.

I have a theory about why the Wi-Fi board in the CTU often has problems.  The OCXO draws more current when it is warming up, so maybe during this time, the voltage on the 5V net is sagging.  On second thought, that's not it because the OCXO only uses 3.3V.  Still, the 5V net could be sagging anyway, maybe while the GPS is trying to acquire satellites.

OK, I tested the voltage on that net using a barrel-plug connector on the Wi-Fi board.  At the moment it is sagging quite a bit, down at 4.5V.  Let's try a cold boot and see what happens.  It starts at 4.75V and then dips quite a bit as the Wi-Fi module is starting up, possibly due to power consumption from the antenna, or maybe to the GPS module's startup.

Clearly then, the DE3's existing power supply is inadequate to provide the specified 5V to all 3 of the CTU components that use it (DE3, Wi-Fi, and GPS).  This badly needs to be addressed.