Re: Waking up a serial port

bp@www.zefox.net wrote:

HW <none@no.no> wrote:

On Sat, 15 Mar 2025 17:30:03 -0000 (UTC), bp@www.zefox.net wrote:
 

Are there any customary tricks to making a diagnostic serial port
active?

 
I am not aware of any standards.
 
Some devices will respond to a few CR-LF, as in pressing the enter key
a few times, but those are probably mostly intended to be accessible
by the user.
 
A device like this may very well have the serial port disabled in
firmware.

 
I did briefly try to connect a usb-serial adapter, hoping to see at
least garbled boot messages during power up by varying baud settings.
Nothing at all appeared on the terminal screen. That's when I tried
the 'scope and found nothing.
 
There are some board photos at
http://www.zefox.net/~bp/ampinvt/2nd_inverter/board_photos/
Please note it's http:..., not https. You'll have to pacify
your browser if it doesn't like unencrypted connections.

I'm not seeing an MCU, although it could be underneath or on another board.

Sometimes a UART is for the instrument to communicate with some other
device, which is something that would have to be configured somehow.  Or
maybe it's designed to be queried from another device, ie you need to speak
before it will answer.  It's quite likely not designed to work like a
terminal with printable text.  Maybe it's only for use in debugging or
factory test versions of the firmware and you don't have one of those.

There's no way to know in general.

Theo