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[aprssig] Tomtom's For APRS (Question)

Dave dave at g8kbv.demon.co.uk
Mon Apr 2 16:54:08 UTC 2012


Have you ever tried to program to the USB subsystem, using OS API call's?
You might change your opinion if you had.

Then, it's all totally different if you want it to work on another 
platform (Windows vs Linux for instance)

Other than the device naming conventions, RS232 usage is much the same 
between those two OS's.

It's not dificult, but there are **LOTS** of things to trip you up, and 
most of them will de-stabalise the OS too if you get something wrong with 
the USB subsystem..

Also, if you have a native USB device you've created, that you want to 
market, you idealy need to *PAY* for unique VID/PID numbers from the USB 
consortium, a commercial organisation.

There are ways arround it for developers, there is at least one popular 
bit-banged (low speed) USB implementation about using Atmel chips, that 
does work very well (used in a lot of SDR kits) but then you have the 
issue of (possible) clahshes of VID/PID/sn: values so that vastly 
differing bits of kit, all look (initialy) the same to the OS and user, 
causing untold driver confusion.  It's bad enough now, as most of those 
examples masquerade as HID device (mice, keyboards etc) often causing 
upset when connected, and not easy to cleanly sort out and tidy up.

RS232, for whatever reason, is tried trusted and tested.  It "just 
works".  It also has a lot of inbuilt ESD/EMI protection.  USB has issues 
with ESD, as many have found out.  EMI (ingress and egress) is sometimes 
an issue too.

Lastly, USB connectors are bl**dy useles things in the face of vibration, 
such as when mobile, unless you add hardware, they tend to work loose and 
fall out at the mose inconveniant moment.  The resulting softwhere chaos 
takes time to sort out, often needing a OS reboot in the process.

RS232 connectors bolt in if you want, as standard.

If you "Need" USB, then use one of the many USB/Serial converter modules, 
TTL level serial for your project (no need for MAX232 chips) and a good 
robust USB implementation with all the correct bits done.  FYI, that's 
how most of the current GPS RX USB dongles are done.  Serial internally, 
just a USB chip bolted onto an existing product.

Just my take on it, YMMV.


Dave G0WBX.

On 1 Apr 2012 at 18:47, Pat Cook wrote:

> Sounds like what's going to have to happen is TNC's to convert to USB
> since EVERYTHING is going that way.  What is holding back TNC
> manufacturers?  What's holding back RADIO manufacturers?
> RS-232 interfaces (In ANY form) are ANTIQUATED RELICS !!!!!  Time to
> move on.....
> JMO.....
> Cheers & 73 :D
> -- 
> Pat Cook, KB0OXD
> Denver, CO
> KB0OXD Cybershack - http://www.wix.com/kb0oxd/kb0oxd/
> KB0OXD Cybershack Soap Box - http://kb0oxd.blogspot.com/
> EchoLink Node No. 19905 (LINK COMING SOON - 147.465 Mhz. Simplex/100.0
> Hz PL) APRS TRACKER ( NEW !!! ) - http://aprs.fi/KB0OXD (Usually on as
> KB0OXD-5 Via APRSDroid)

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