Re: Waking up a serial port

Jeff Liebermann <jeffl@cruzio.com> wrote:

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

While looking around inside a 12 volt to 120 volt inverter charger
I noticed a pin header labeled "5v Rx Tx Gnd" near the edge of the
main circuit board.

 
That sounds more like a USB-A connector pinout:
<https://components101.com/sites/default/files/component_pin/USB-Type-A-Connector-Pinout.jpg>
 
See if there's any data on the Rx pin.
USB data runs at 12 to 480 Mbits/sec.  What's the maker and model
number of your oscilloscope?  What's the scope bandwidth?
 
If the connector is USB, the data is differential between the + and -
pins (which may be the Rx and Tx pins).  RS-232 is specified at
+/-15VDC.  It's possible for it to operate at 5VDC.
 
<https://www.testandmeasurementtips.com/measuring-universal-serial-bus-usb/>
 
The inverter manufacturers name and model number would also be
helpful.  Good luck.
 
Begin Mini_Rant()
1.  What problem are you trying to solve?  (Keep it simple)

I'm trying to figure out if I can talk to the controller

2.  What do you have to work with?  (maker, model, versions, photos,
URL's)

Owon vds1022i usb scope, 100Ms/sec, likely 10 MHz bandwidth. Board
images are at
zefox.net/~bp/ampinvt/2nd_inverter/board_photos
It sure doesn't look like a USB port to me. If it is, my scope is blind.

3.  What have you done so far and what happened?

Connect the 'scope, power cycle the inverter, look for traffic on Tx.

4.  What is your ability or experience level?

Retired experimental physicist, from the pre-digital epoch.

5.  Optional - All the background data and history.

The inverter behaved strangely (but usably) when acquired. Eventually
I replaced it with another unit and would like to understand what ails
this one if it isn't too difficult. It's still usable as a spare, so
I'd rather not damage it.

My working guess is that the software is misconfigured. The vendor's
behavior was completely obfuscatory (if that's a word) so I'm not asking
them for anything. Their products are sold cheaply enough that buying
three to get two that work was still the best deal available.

End Mini_Rant()

Thanks for writing,

bob prohaska