Objective Development Forums

Re: V-USB speed

2009-09-24T13:28:04+02:00

For a serial port, yes. Except that you must divide by 10 instead of 8 due to start and stop bits.

For USB, look at the figures people report, or make your own experiments. It's hard to predict how fast V-USB will be in a particular application.

Statistics: Posted by christian — Thu Sep 24, 2009 1:28 pm

Re: V-USB speed

2009-09-24T00:23:55+02:00

Can you tell me if i'm correct:

using serial port at 115.2 kbits

115.2 kbits / 8 = 14.4 kBytes

Use an ADC with 10bits i need 2 bytes to send a sample from micro to pc, so 14.4 KBytes / 2 = 7,2K samples per second?

That is the maximum rate of samples from micro to pc?!

Statistics: Posted by Guest — Thu Sep 24, 2009 12:23 am

Re: V-USB speed

2009-09-23T23:33:01+02:00

Hi, i will have to transfers some information from adc to computer to make a graphic. You project will give me a very good start point, thanks. It's easy to use visual basic with it?

Statistics: Posted by Guest — Wed Sep 23, 2009 11:33 pm

Re: V-USB speed

2009-08-31T18:54:48+02:00

this isnt my library. The #USBLib library which has been updated is here

http://tommyfive.untied.de/usblib/

my library sits on top of this. If you give the name of the V_USB device , it scans for it and then allows you to send control messages to it.
If you want mine , i can upload it. Specify where you want me to upload it.

Statistics: Posted by spiky — Mon Aug 31, 2009 6:54 pm

Re: V-USB speed

2009-08-30T14:27:39+02:00

Hi Spiky,

i'm interested in looking at your C# code [libary], but having trouble accessing the mediafile site. Is there any alternative

Thanks,

Statistics: Posted by Guest — Sun Aug 30, 2009 2:27 pm

Re: V-USB speed

2009-08-13T16:24:44+02:00

I had never thought of that ! i have only windows XP at home. If i test it in other platforms , i'll drop a note here.
Thanks for all the support.

Statistics: Posted by spiky — Thu Aug 13, 2009 4:24 pm

Re: V-USB speed

2009-08-10T19:23:18+02:00

I don't say it's impossible. Just that you should test on various platforms before you publish something. Control endpoints may be different from the bulk endpoints used in AVR-CDC. And even if it does not work on all platforms, it may be worth publishing. But you should add a note, otherwise you'll get lots of e-mail...

Statistics: Posted by christian — Mon Aug 10, 2009 7:23 pm

Re: V-USB speed

2009-08-10T19:17:05+02:00

Sad. It worked so well for me and my friend. Better than a USB - RS232 converter we had bought a few weaks ago.

I suppose time critical tasks which require USB interrupts to be disabled at certain times are not possible on all hosts. I was hoping i could find a way to do that without having to use another AVR.

None the less , my efforts have not been in vain. In the very least , it works in my PC !

Thank you very much for all the information you have provided.

Statistics: Posted by spiky — Mon Aug 10, 2009 7:17 pm

Re: V-USB speed

2009-08-09T21:08:57+02:00

Regarding AVR-CDC: No, it does not work well. MANY people have problems where the device stops working all the sudden and the endpoint is stalled. This occurs most likely on Windows, other operating systems don't stall the endpoint on the first transmission error.

Statistics: Posted by christian — Sun Aug 09, 2009 9:08 pm

Re: V-USB speed

2009-08-08T10:26:25+02:00

@ali_asadzadeh , i've written no documentation. but it should be easy as i'm giving you the source. There's nothing much in my library. It keeps attempting the control transfer for 100 times. You need SHarpUSBLib as well.

http://www.mediafire.com/?sharekey=f59081471384dbb2b94117dade8fc295e04e75f6e8ebb871

@Christian ,
Thanks for replying.

Transfer rate : I did not know that transfer rate depended on the OS. I was under the assumption that most OSes can easily manage max speed for atleast low speed USB devices. Looks like a lot more happens and its not as simple as i had thought. I can live with 8 kB/s though should the speed ever drop down.

I tried transferring a 480 kB file from the PC to an mmc card using V-USB and i obtained 16.5 kB/s average speed. I transferred 512 bytes from the PC to the atmega16 at a time and then transferred 512 bytes to the MMC card. So i think PC -> atmega16 through V-USB was taking place at 24 kB/s. The average speed was lower as part of the time was spent only doing transfers to MMC card.

Interrupts : Thanks for the tip. I think this method should work well with other environments as well. It seems like the same technique albeit for a shorter period of time is used in AVR - CDC project. AVR CDC also relies on the host to reattempt transfers when the device is servicing the UART. AFAIK , AVR CDC works well even in windows vista.

Statistics: Posted by spiky — Sat Aug 08, 2009 10:26 am