No stamp found... here we go again, and again... Editorial rant
vaclav_sal
Posts: 451
It is a common knowledge that EIA 232 / RS232 standard is not always followed by industries.
However, Parallax is pretty consistent when using DSR (data set ready) and RTS (request to send ) to verify hardware connection between the PC data terminal and Stamp processor - data set.
On DB 9 connector these are pins 6 (DSR) and 7(DTR).
RTS is originated by the editor (PC) and DSR is returned by shorting pins 6 and 7 of the DB9 connector on the processor side.
This EIA standard in implemented in Windows OS as COMx ( communication ) port.
These are industry standard, but as I pointed out, apparently not followed when it comes to emulate COM using USB technology.
It is not clear why either Windows OS or Parallax would quit following the EIA standard, especially when emulating COM using USB.
The only explanation we get from Parallax is carefully worded statement that here are other means of identifying the COM port used by OS..
As a result of this voodoo technology, without proper documentation, we have come to rely on using only Parallax USB to COM converter and generally ignore the editor error / progress messages when initially connecting to the Stamp.
Cheers Vaclav
However, Parallax is pretty consistent when using DSR (data set ready) and RTS (request to send ) to verify hardware connection between the PC data terminal and Stamp processor - data set.
On DB 9 connector these are pins 6 (DSR) and 7(DTR).
RTS is originated by the editor (PC) and DSR is returned by shorting pins 6 and 7 of the DB9 connector on the processor side.
This EIA standard in implemented in Windows OS as COMx ( communication ) port.
These are industry standard, but as I pointed out, apparently not followed when it comes to emulate COM using USB technology.
It is not clear why either Windows OS or Parallax would quit following the EIA standard, especially when emulating COM using USB.
The only explanation we get from Parallax is carefully worded statement that here are other means of identifying the COM port used by OS..
As a result of this voodoo technology, without proper documentation, we have come to rely on using only Parallax USB to COM converter and generally ignore the editor error / progress messages when initially connecting to the Stamp.
Cheers Vaclav
Comments
-Phil
German Proverb : Whose bread I eat his song I sing.
Cheers
Vaclav
I'd say that's a pretty unfair assertion in this case.
Use a good USB-to-RS232 with an FTDI chip and you won't have these issues, you aren't limited to getting something from Parallax.
C.W.
That's a bit insulting, you know.
Parallax uses FTDI chips for everything that I'm familiar with. FTDI hardware and software seems to consistently work better than many other adapters. I try to stick with FTDI when I can (not always possible) and have never run into any problems with them. This is for things from Parallax and elsewhere.
I have had many, many issues with other USB/serial adapters. I don't touch the really cheap ones you can get. Sometimes they work, sometimes they don't. It's usually not worth the hassle.
You are eating German bread?
But you all missed the point that many beginners ( OK I did not say that) strugle with the issue of communicating with the Stamp especially when USB adapters are used.
So I will point that to you again:
As a result of this “voodoo” technology, without proper documentation, we have come to rely on using only Parallax USB to COM converter and generally ignore the editor error / progress messages when initially connecting to the Stamp.
And for all of you who just skim over things _ I got nothing bad to say about Parallax COM to USB adapters.
Similar problems with the picaxe chip needing a specific USB to serial chip because some chips don't implement all the serial pins.
Possibly similar problems with the standard propeller chip and after much discussion it was found that the polarity of the reset line works better with the polarity inverted so it resets on the negative edge rather than the positive edge.
I agree that it is voodoo, and it took a *lot* of sleuthing to find that solution (thanks to pullmoll from Bonn. The solution was to swap the NPN reset transistor for a PNP one.)
I am looking at the stamp schematic here http://www.parallax.com/dl/docs/prod/schem/bs2revf.pdf
The reset circuit is similar to the propellers with a R/C network. These R/C network solutions may be a cause of problems because the RS232 specification allows for +/-3V but it could be +/-12 V or even more, and with a USB adaptor it is likely to be +/-9V. All these values are valid RS232 signal levels, but they will clearly give different time values.
Then there is another issue with joining pin 6 and 7. Maybe these lines are not connected on all USB to serial devices? Or maybe they are implemented but the driver software does not know how to use these lines?
One almost needs a RS232 breakout box, measure the volts on every pin, and RS232 port sniffer software.
You seem to be missing a point as well. Parallax supplies a good solution, but there are other FTDI RS232 to USB adapters available. It is just hard to know what is inside one without buying it and trying it.
Parallax is not forcing you to buy their adapter, but they cannot assure that others are complete. Historically, some vendors created adapters that only had RX and TX, without the other lines. Those are no good.
I happen to have 3 or 4 adapters that work - only one is Parallax. Others include an Arduino programmer that has a serial interface as an extra. Another is an off the shelf Taiwanese brand that happened to be FTDI.
The real concern here is your title "No stamp found....." This is the most common problem that beginners have and Parallax is more than willing to help the beginner get into a "Hello World" status. But if one choses USB for a programming port over RS232, one has to buy or build a programing adapter that will provide all 3 signals.
The BasicStamps were in production before USB ever existed and can do very well without an adapter by using an existing RS232 port.
"Other means..." of confirming functionality of the RS232 to USB conversion includes free public software such as MINICOM in Linux. Windows and Apple OSes tend to sell these kind of mini applications, but some Linux versions are compiled for all three OSes.
I have never used the Parallax Serial adapter . I use a FTDI based USB-19HS from keyspan ( part of trpp light ) I have NEVER had a issue with it !
Peter
I've been programming for many more years then I care to admit, and in most cases, longer then some here are old. In the tenure of my programming, I've established "habits" for communications with devices attached to PC's. I can honestly say when one mixes technology of different methodologies one will have more problems. In short and to the exact point: If the device has RS232, then use a RS232 to talk to it. If the device is USB, then use the USB to talk to it. USB->RS232->USB... Yeah... right... that says "I'm big, bad and brave, I can handle the the possible problems"
Just an humble opinion.
KK
KK,
Problem is most PC's and Laptops no longer have a RS232 port, leaving USB -> RS232 as the primary option.
C.W.
I read somewhere (here, maybe?) that some motherboard serial ports are now implemented as USB hardware anyway - they have USB-Serial hardware on the motherboard rather than true serial interfaces. I don't know if it is true or how prevalent it is, but it does add one more interesting twist.
Some time ago I purchased an IO card with dedicated uarts, an actual serial card, that I've keept over the years. It works wonders.
Maybe it's time for me to start playing with more moderen PC's when at home... (At work it's much different...)
KK