USB to RS-232 adapters are cheap now....
Gary Peek
cheap enough that in some cases it is crazy to try to
make your own USB interface to your board.
http://www.buyextras.com/usbtoserial.html
cs_po...@hotmail.com
Not unless you have another reason for having the RS232 level
translators on your board.
Otherwise you can buy a USB-serial chip such as the CP2102 to use in
place of the level translator for $4.03 in singles from digikey.
Granted the package is a little harder to hand solder, but our techs
get them on there somehow.
But if you are just putting together a hand wired project, or already
have to support RS232, then yes, the dongle cable makes sense. Too bad
I bought my personal one before the prices dropped...
linnix
Despite the cheap and easy solution, there are other considerations:
1. USB connectors are smaller for PCB.
2. USB has power hookup.
3. USB allow custom ID for automatic driver loading.
Mike Harrison
FTDI have a neat solution for applications needing a captive USB lead - a USB cable with their chip
in the plug and a 0.1" header on the end :
http://www.ftdichip.com/Products/EvaluationKits/TTL-232R.htm
They also do a little module with the USB B socket with the chip underneath :
http://www.ftdichip.com/Products/EvaluationKits/MM232R.htm
jmk
> http://www.ftdichip.com/Products/EvaluationKits/MM232R.htm
I just got a couple of those inhouse last week for testing. Don't know
just how well they will actually work in practice, but they sure are
"cute." <G>
Kevin D. Quitt
Be careful. Last I checked, their serial port emulation was a bit off, and caused us some
problems (i.e., disconnecting the device).
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Mike Harrison
>On 1 May 2006 12:36:36 -0700, "jmk" <james...@l-3com.com> wrote:
>
>
>>> They also do a little module with the USB B socket with the chip underneath :
>>> http://www.ftdichip.com/Products/EvaluationKits/MM232R.htm
>>
>>I just got a couple of those inhouse last week for testing. Don't know
>>just how well they will actually work in practice, but they sure are
>>"cute." <G>
>
>Be careful. Last I checked, their serial port emulation was a bit off, and caused us some
>problems (i.e., disconnecting the device).
I'm using these now in prototypes of a couple of products - work fine, as did their predecessor
chips.
I suspect that disconnecting will always be problematic to some extent, especially if done when the
application software doesn't know about it...
I've not used their serial port emulation drivers though, as the D2xx drivers they provide are much
more controllable. COM port emulation over USB can never be perfect due to the differing nature of
the 2 beasts...
Meindert Sprang
news:qiqc52po6npl17i1t...@4ax.com...
> Be careful. Last I checked, their serial port emulation was a bit off,
and caused us some
> problems (i.e., disconnecting the device).
That is, IMO, always a problem with the application opening the com port,
not expecting the com port to disappear. IOW, a programmers' fault.
Meindert
Mat Nieuwenhoven
Are these adapter USB-to-RS232 ot USB-to-PC serial port converters? In other
words, can they only be used as a classical PC serial port for asynchronous
data? The reason I'm asking is that I use some synchronous serial links for
which I need special hardware. Being able to use USB sure would be nice.
Mat Nieuwenhoven
Mike Harrison
wrote:
The FTDI ones are USB to TTL-level async, i.e. to feed directly into a PIC etc. UART.
The FTDI chips also have various modes to implement other data formats, and I think sync serial is
peobably one of them - have a look at the 'bit-bash modes' in the data.
CBFalconer
>
... snip ...
>
> Are these adapter USB-to-RS232 ot USB-to-PC serial port converters?
> In other words, can they only be used as a classical PC serial port
> for asynchronous data? The reason I'm asking is that I use some
> synchronous serial links for which I need special hardware. Being
> able to use USB sure would be nice.
What is the difference, in your mind?
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cs_po...@hotmail.com
> Mat Nieuwenhoven wrote:
> >
> ... snip ...
> >
> > Are these adapter USB-to-RS232 ot USB-to-PC serial port converters?
> > In other words, can they only be used as a classical PC serial port
> > for asynchronous data? The reason I'm asking is that I use some
> > synchronous serial links for which I need special hardware. Being
> > able to use USB sure would be nice.
>
> What is the difference, in your mind?
Synchronous serial requires a clock bit, but has a simpler receiver
architecture since you use the clock to sample the data. A
microcontroller that offers both synchronous and asynchronous serial
modes usually uses different peripheral functions to do each, with
differnt package pins assigned. Though it would be possible to design
a block that could implement either type with some pins shared between
the two.
Using the USB to get a few bits of parallel I/O and then trying to
bit-bang synchronous serial is probably not a good idea, because the
latency of the USB is too high - you would be limited to fairly low
effective baud rates. Though that may work for some applications. Too
bad, because some of the USB-serial chips do have extra I/O bits next
to the UART function.
ammo...@cc.full.stop.helsinki.fi
> Are these adapter USB-to-RS232 ot USB-to-PC serial port converters? In other
> words, can they only be used as a classical PC serial port for asynchronous
> data? The reason I'm asking is that I use some synchronous serial links for
> which I need special hardware. Being able to use USB sure would be nice.
FTDI's FT2232 chip has two serial interfaces, one of which supports
synchronous transfers. You can get DIP modules from DLP Design.
<http://www.ftdichip.com/Products/FT2232C.htm>
-a