Re: error Win7 / Serial Port / Direct Connect - comm error inv/corrupt data from con
- The software automatically configures the port baud rate, data bits, stop bits, and also raises the RTS and lowers the DTR. These lines may "toggle" if the serial communications fail at some point (the console does not respond for example). The La Crosse console will not transmit unless it sees these in the proper state.
The RTS and DTR lines are used to create a "virtual ground". As mentioned in other posts, the voltage levels used on the handshakes may be critical given La Crosse's virtual signal ground. The TX line out of the console is therefore relative to the midpoint between the RTS and DTR voltages. Is this a hack? Certainly. They are also probably using this scheme to draw parasitic power to drive there communications circuit in the console. Because they wanted to use cheap RJ plugs and the 4 conductor telephone cord, this limited their options. I also suspect that they are not using a real UART and are reading the state of and controlling the output of generic I/O lines on a PIC controller to further reduce costs.
If the USB adapter does not actually have these handshake lines (RTS and DTR), it will not work. Many of the cheaper ones do not support the handshake lines. That is why I always recommend the IOGear because I know they do support these lines and the driver seems to be well written compared to others than often create the dreaded Windows Blue Screen of Death (BSOD).
If you have a meter you can verify whether the RTS line is being correctly managed. You can run WUHU them stick a paper clip in the RTS of the DB9 and measure it against the PC case (or the signal ground pin of you want to get technical about it). You should see a voltage of either +12vdc or -12vdc (I think -12vdc is logic true or on). If you see something in the 5vdc range, that is probably the problem. If you are seeing zero volts, you know that the handshake hardware is either not supported or the driver is not really supporting the Windows API to control the lines.
--- In firstname.lastname@example.org, "abscam_man" <cjdewberry@...> wrote:
> The cable is the same cable that shipped w/ the LaCross unit and it worked fine in my previous incarnation of weather station (IBM laptop). Due to equip faliure and booting an old XP desktop, I've been trying to get the new HP Win 7 system to communicate with the LaCross 23xx system.
> Serial to USB failed - likely due to crap standards.
> Serial card works fine in the PC system. But sounds like there are a number of variables which can cause problems. One of you mentioned hardware controls, but I've yet to find anything about the serial port settings 9600 8, N, 1, none or some derivation.
> Or is it as simple as a battery issue - which I saw as a culprit somewhere else?
> Yep - frustrating...I have had this thing in steady state for about two years and now its fubar and my few neigbors that have come to rely on the Wx data are sad. :-)
> Readout this morning:
> Mon Jan 31 08:02:38 2011 > WUHU Application Started (1,0,216,174)
> Mon Jan 31 08:02:38 2011 > WUHU monitoring started (WUHU21623XXSP).
> Mon Jan 31 08:02:38 2011 > Weather Underground ID: KCAWALNU10
> Mon Jan 31 08:02:38 2011 > Opened serial port COM1 successfully.
> Mon Jan 31 08:09:53 2011 > Communication failure: Could not retrieve the console's clock value.
> Mon Jan 31 08:09:53 2011 > Cannot retrieve console history because the PC clock and console clock are too far out of sync. or the console clock could not be read.
> Mon Jan 31 08:09:53 2011 > Console history was not read completely. 0 records were collected. 0 records were stored. 0 records were uploaded to Weather Underground, 0 records were uploaded to PWSWeather, 0 records were uploaded to WeatherBug.
> Mon Jan 31 08:10:29 2011 > An error occurred reading the storm alert from the console.
> Mon Jan 31 08:10:29 2011 > Time to next console communication: 5000 milliseconds.
> --- In email@example.com, "Ken" <yahoo@> wrote:
> > Serial communications came from the dawn of computing. There were no standards to speak of. There were no smarts to devote to the user experience. Even the voltage singles are amorphous.
> > So, when you say you swapped cards and it isn't working, that is what was/is experienced in every new install. Serial was and is a sack full of cats.
> > LaCrosse requires hardware handshaking. If you have the specs, you can load the terminal applet and validate your interface. But for most you'll need to depend on the manual and hope you and the hardware are capable of making that spec happy.
> > Most folks come to this topic with frustration and even anger. Relax a bit and know you are facing an ancient problem that will probably resolve with some effort. I'll let Heath do the specifics because he handles it almost daily.