Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: bp@www.zefox.net Newsgroups: sci.electronics.repair Subject: Re: Waking up a serial port Date: Sun, 16 Mar 2025 00:50:18 -0000 (UTC) Organization: A noiseless patient Spider Lines: 57 Message-ID: References: Injection-Date: Sun, 16 Mar 2025 01:50:19 +0100 (CET) Injection-Info: dont-email.me; posting-host="c4f156961f323101988ab78dba3afec0"; logging-data="711058"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX199hEk3FfB1bKQkP4Wg3MlFytG0HNk0GNY=" User-Agent: tin/2.6.4-20241224 ("Helmsdale") (FreeBSD/14.2-STABLE (arm64)) Cancel-Lock: sha1:svZb85Tf8aBBPq95aYEiON6tzik= Bytes: 3202 Jeff Liebermann 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: > > > 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. > > > > 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