LPC1778 ISP mode autobaud possibility of power glitch

Discussion created by lpcware Employee on Jun 15, 2016
Content originally posted in LPCWare by arion2000 on Mon Dec 07 19:01:51 MST 2015

I am currently facing an issue with autobaud related issue when trying to flash in firmware using flash magic. This issue is rather interesting as it has a different behavior than what was commonly discussed here:

The issue I faced was that when you power on the board initially from cold, where the board would run into autobaud error during the firmware flashing operation. At this stage, what was observable was that when you send a "?" in ISP mode, you would not receive a "Synchronized" reply from the MCU. You would be seeing the transmit LED from the MCU flashing but autobaud error message will appear.

However, if you were to unplug and replug the power immediately, the autobaud error would be gone and firmware flashing operation through flash magic can be carried out. I did some waveform capture in order to check out what is going on, but if it is power glitch related, what else can be done on my end in order for me to narrow down the possibility of what is causing this?

In the attached picture Signal 1, channel 1 is the BLOAD pin of LPC1778 Pin 2[10]. While channel 2 is the RSTOUT signal showing a glitch. In Signal1, this is the observation I made when the autobaud will fail.

In the attached picture of Signal 2, top wave is BLOAD while bottom is RSOUT signal. Signal 2 is the observable wave that autobaud issue will not occur.

I am unsure if these were the power glitch cause here.
I would like to know, is that are these the cause of the autobaud failure? How do I narrow it down further? Obviously the criteria mentioned by the user manual has been fulfilled otherwise I totally would not be able to flash my firmware at all. I am thinking this is probably some boundary condition that has been hit that is causing this. Hope you guys could help. Thanks.