ekerin

Small update: I charged a 0.1F supercap to approx 2.9v, and disconnected the power from my board. Since last night (8 hours) it's down to 2.03v. Clock is still in sync (within reason for a crystal oscillator). Datasheet says 1.8v is the low point for vBAT. I just restarted my test, with the supercap fully charged to 3.3v. Let's see how long it will run. Edit - 12 hours later. Supercap is at about 1.82v. So not too bad!

I've recently started using the real time clock on the TM4C1294. I have the clock working, keeping time, and set with NTP. I want to try and make it a battery backed RTC though. I'm currently wasting time in an airport, so I can't test. From the schematic, it looks like if I remove R39, and connect a battery to TP11 and gnd - I should be able to keep the clock going while the board is powered down. Has anyone tried this, or done it with a custom board? Edit - Oct 10th. Finally got a chance to try it, and it does work! I put 3.3v from the bench power supply on TP11, with