On Wednesday 10 December 2003 08:38am, Paulo Marques wrote: > Marr wrote: > > On Monday 08 December 2003 03:59pm, Alessio Sangalli wrote: > >>... > >>if I connect a usb-serial adapter to my laptop, and I connect to this > >>adapter an external serial modem, everything's perfect. But, if I > >>connect another device, for example a telescope, (which happens to have > >>only 3 lines connected, TX, RX and GND) I can't send or receive > >>anything. The same hardware works well in windows and I can access the > >>telescope using minicom on a desktop computer with a real serial port. > >> > >>Do you perhaps think that, the pl2303 doesn't work well with devices > >>that implement a 3-wire only communication? Is there somothing to do? > > > > This sounds (almost) exactly like the problem I had with the Belkin > > F5U109 USB/RS-232 adapter. > > > > In short, output data gets held up in the USB/RS-232 adapter for RS-232 > > devices which don't assert the 'CTS' signal. > > ... > > If this is the problem you can try to build a "special cable" that shorts > RTS/CTS and DTR/DSR on the PL2303 side (pins 4-6 and 8-7), and connects > directly TX, RX and GND (pins 2,3,5). > > This way the device gets is own handshake. This is a simple test that can > verify the source of the problem, or even solve it if you're happy with the > solution :)
Excellent point. This is essentially what I did initially (with a crude self-made RS-232 breakout box) while testing the problem to determine which RS-232 signal was the problem. In my case, the 'CTS' signal was the problem. DTR/DSR wasn't an issue, but Alessio's telescope could certainly act differently from my GPS, so it's worth investigating. In fact, I later received this private reply from Alessio, so your technique solved his immediate problem. In the interest of archiving the fact that this worked for him, I'm reproducing part of his email here: On Thursday 11 December 2003 08:34am, Alessio Sangalli wrote: > Anyway, I've solved the problem as suggested by another user: I've > shorted together RTS/CTS and DTR/DSR on my serial connector and now I > have a "fake" handshake that works very well :) Of course, fixing the driver (if possible) is the proper long-term solution, so if I can get my hands on a PL2303-based USB/RS-232 adapter sometime, I'll try to "cure the disease" (like I did to the 'mct_u232' driver used by my Belkin F5U109 adapter) instead of "treating the symptoms", assuming I can duplicate the problem with my GPS receiver. Aside: (once again, for clarity of the archives for future readers): The pinouts Paulo mentioned above are for a DB-9 RS-232 connection, not a DB-25. Bill Marr ------------------------------------------------------- This SF.net email is sponsored by: IBM Linux Tutorials. Become an expert in LINUX or just sharpen your skills. Sign up for IBM's Free Linux Tutorials. Learn everything from the bash shell to sys admin. Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
