Bug#704242: Fwd: Re: Bug#704242: Driver for PL-2303 HX not working
Hello Greg,
Am 24.06.2013 20:56, schrieb Greg KH:
But wiring that up to a "real" 9pin serial port would be a pain (doable,
but a pain). Is there any devices out there with a DB-9 output
connector?
You mean if you want to test full handshake with all signals - that's true.
Which is what the driver needs to test, right? And of course, everone
with this problem is properly hooking up these signals, right?
I can't speak for all applications but i never use the hardware handshake for data transfer.
As i have written i don't know applications that will do it. Like most of the older mobile adapters.
That's the reason why this PL-2303 HX adapter has no handshake signals outside.
Maybe some people abuse this input and output lines for IO purposes like for programmers.
One time is tried such an adapter like this but it does not work. ;-)
http://www.lancos.com/siprogsch.html
(I tried not to use it with an usb serial interface - i used a good and old PC UART.)
Otherwise, there will be problems as the pins could float and cause
transmissions / receive data to stop happening.
This should not happen if handshake is disabled.
In the case of this PL-2303 HX adapter it worked with windows and the older kernel without handshake.
But of course it is better when everything is tested.
At the least, loop-back testing is important.
This test is sufficient to see if the problem occurs.
The advantage of the adapter is to get directly 5V and 3,3V.
What do you mean by this?
Normally you use this adapters to transfer data from a microcontroller.
It is very useful when you have direct the necessary power supply for the microcontroller.
The PL-2303 can work with 5V and 3.3V logic and this adapter has also a 3.3V output for some mA.
I don't know some other adapter with exactly this chip, because i don't need them.
Only this Adapter which use the other chip ch341-uart which works without problems
http://www.ebay.com/itm/USB-to-RS232-Serial-9-Pin-DB9-Adapter-PC-PDA-RS-232-/180399132966
When i think about it i never seen that someone uses the handshake for this simple serial communication.
Not in communication with mobiles, ARM-boards or AVR microcontroller.
The built-in UART's in the ARM and AVR don't suffer handshake
signals, so that you must do it by software with additional IO
ports.
What's wrong with software flow control?
Nothing is wrong with it!
I just want to say that in most applications nobody use it.
You communicate from a quick PC to a slower microcontroller with at least slow data rates.
The microcontroller has an IRQ on the UART you can use for incoming data.
So this works normally without any problems and additional handshake.
Why reinvent something that
has been successfully used for 30+ years?
Before 30 years computers where slow and without a multitasking OS.
So you need handshake when you don't want to loose data.
i think you misunderstand me.
thanks,
greg k-h
Regards
Karsten
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