USB to RS-232 adapters are cheap now....

Just to let you know, USB to RS-232 adapters are getting cheap enough that in some cases it is crazy to try to make your own USB interface to your board.

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Reply to
Gary Peek
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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...

Reply to
cs_posting

Despite the cheap and easy solution, there are other considerations:

  1. USB connectors are smaller for PCB.

  1. USB has power hookup.

  2. USB allow custom ID for automatic driver loading.
Reply to
linnix

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 :

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They also do a little module with the USB B socket with the chip underneath :

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Reply to
Mike Harrison

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."

Reply to
jmk

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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Reply to
Kevin D. Quitt

caused us some

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...

Reply to
Mike Harrison

and caused us some

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

Reply to
Meindert Sprang

:

caused us some

their predecessor

especially if done when the

they provide are much

differing nature of

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

Reply to
Mat Nieuwenhoven

... snip ...

What is the difference, in your mind?

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Reply to
CBFalconer

underneath :

caused us some

their predecessor

especially if done when the

they provide are much

differing nature of

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.

Reply to
Mike Harrison

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.

Reply to
cs_posting

FTDI's FT2232 chip has two serial interfaces, one of which supports synchronous transfers. You can get DIP modules from DLP Design.

-a

Reply to
ammonton

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