Objective Development Forums

I think the exchange rate is determined by the operating system on the PC and how quickly it polls the USB port. Obviously there is an upper limit imposed by the speed of USB too.

OK I did remember eventually. But in usbport.sys in W10 I can't find any of the relevant byte sequences.

So I did some research and it appears that Microsoft has removed the poll rate limitation in Windows 10.

I am guessing (it is only a guess) that it will be similar to 7 and Vista; but at a different location and with a slightly different byte sequence. Next week I may have time to take a look if that will help (and if I remember!).

Glad you found the answer and that it worked for you too!

Thanks for that - looks great. I imagine it must be similar on Vista; will do some work on that when I get a chance. (edit) On Vista the location is different (on mine it was 01f824) and the byte sequence is slightly different too: 3C 08 73 09 C6 86 1E 01 00 00 08 Note the two 08s are in the same re...

There is nothing that can be done on Windows 7. I don't know about Windows 8.

Unfortunately that patch only helps mice, I eventually discovered. This is a real problem on Windows and really the only option is to use something else in most cases. Windows XP has a higher polling speed, but the application I run needs a minimum of Windows 7 and ideally Windows 7 64-bit.

Strangely I did once experience a double letter problem. A dot matrix printer would print a corrupt line if you had a double letter "t" anywhere on it. You had to be careful what you wrote!

Hi thanks for that. Nice to have it confirmed that I wasn't doing something wrong! I have my project all working now but the latency is too high. I'm using Windows 7 and know it would be better with Linux and its 2mS poll time, but to be honest I will probably go to a USB hardware solution like the ...

So what problem are you having?

Glad to hear you got it working. Perhaps this topic might be of use to someone else in the future too. Great!

Sorry - misunderstood.

I believe it's simply the pull-up resistor on the D- line that causes Windows to detect you have plugged something in. Check you have the D+ and D- lines the right way round - the correct colour coding is in Wikipedia, but the first Google hit for the image search has the green and white reversed (o...

Ah OK. Even on a Windows machine it should detect you plugging it in, that is just a question of the voltage levels, or something. It should come up with an error message, about a device that has malfunctioned, even if nothing works on your board. The D- and D+ should have square waves (or rather, s...

I don't know Linux so I don't know what kernel message you should see.

Are the basics correct? You're using a 12 MHz crystal and 5V supply? Is your device powered from the USB?

Have you gone through all the settings in the config file?