Nucleo F401 only works right after flashing, not after power cycle

Using official F401 bin.

All I get after flashing is "Connected" and a single >.

I remember the issue with drag and drop, so I've tried both drag and drop and ST-Link flashing, no joy either way. Anyone know what's wrong?

The ones from my nightly builds seem to work...

Did you update the firmware on the Nucleo itself? ST decided to add extra checks to their bootloader which makes it refuse to upload perfectly working code.

I was hoping they'd revert them, but presumably they haven't.

Bug here: https://github.com/espruino/Espruino/issues/742

Hm, in fact, that doesn't seem to explain things. After I flash, it does actually work, until I power cycle it, at which point it stops working again. Mysterious. I continue to investigate.

Log from incident, this was the first time I was able to connect and get more than just the > after flashing several times, and trying to connect without powercycling:

Connected
>I˅lInvalid saved code in flash!
>
=undefined
>  //Oh hey, it's not non-responsive. Better reset() and save()!
=undefined
>reset()
=undefined
 _____                 _
|   __|___ ___ ___ _ _|_|___ ___
|   __|_ -| . |  _| | | |   | . |
|_____|___|  _|_| |___|_|_|_|___|
          |_| http://espruino.com
 1v85.75 Copyright 2016 G.Williams
Espruino is Open Source. Our work is supported
only by sales of official boards and donations:
http://espruino.com/Donate
>save()
=undefined
Erasing Flash...
Writing.....
Compressed 86016 bytes to 2657
Checking...
Done!
>
=undefined
>  //great, I'll disconnect, unplug+replug it, and reconnect.... 
Disconnected
Connected
> //and now this is all I see, typing has no effect. 
Disconnected
Connected
>

Any ideas?

Erase all flash and start over...

No change. Erased using ST-Link, flashed again using ST-Link (which as I understand should write it correctly? I thought that was the conclusion above?)

Same behavior on official and my nucleo nightly.

Not sure what to suggest - so it's also broken on the 1v85 release?

What happens if you hit reset? On the nucleos a reset won't cause USB to be disconnected, so you'll see anything that gets written, even if it is only a few characters.

... and it's not just that you set baud rate to 115200 for ESP8266 and didn't change it back?

I'll check reset.

Baud rate is unchanged - and as shown in the log, it worked briefly, and then went back to not working. I don't think i've ever changed the baud rate that the IDE uses - I always hopped on hterm to set the wifi stuff, and then just connected over telnet.

Does the onboard LED flash just after reset? That should show that Espruino finished initialising the hardware.