Very slow reading from Maple Mini

Windows XP,Vista,7,8 and 8.1 etc
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lsturtevant
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Joined: Tue Jul 19, 2016 6:49 pm

Very slow reading from Maple Mini

Post by lsturtevant » Tue Jul 19, 2016 7:06 pm

Hi everyone.

I'm working on a project that is using a Maple Mini. I used the wdi-simple.exe program to install the drivers. I see that it's using window's usbser.sys driver to do the actual communication. The device appears as a Virtual Com Port in the device manager. I can open the device and communicate with it without any problem. It performs all of it's functionality without problem.

My problem is that under windows, reading from the device is very slow. The device streams data to the HOST PC. The rate that it streams at is based on a configuration parameter that I send to the device. The problem is that I cannot read the data faster than about 2800 bytes/second under windows. This is much slower than what's possible for the device and for the usb interface. I've tried everything that I can think of to fix this, but I'm coming up short.

My program uses Qt's QSerialPort class to interface with the device. Under Linux and MacOSX, I can read at the maximum data rate the device supports which is about 160KBytes/second. Under windows, it can't get anywhere close to this. I've tried not Using QSerialPort and opening the device directly using the windows Comm port functions. I get the same result. I've even tried not using the usbser.sys driver. Instead I've used the libusb-win32 driver and opened a connection to the device that way. I get the same result, I can read the data, but it's at a very slow rate.

At this point, I'm out of ideas to try. What could I be doing wrong that's causing the device to read data at such a slow rate. Any help would be much appreciated.

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RogerClark
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Re: Very slow reading from Maple Mini

Post by RogerClark » Tue Jul 19, 2016 9:33 pm

There is a thread about Serial USB speed

I got really high data rates, but you have to write big blocks of data e.g. 128 chars at a time, but lots if small writes

lsturtevant
Posts: 2
Joined: Tue Jul 19, 2016 6:49 pm

Re: Very slow reading from Maple Mini

Post by lsturtevant » Tue Jul 19, 2016 10:42 pm

RogerClark wrote:There is a thread about Serial USB speed

I got really high data rates, but you have to write big blocks of data e.g. 128 chars at a time, but lots if small writes
Thanks for answering,

Are you talking about doing these writes on the Maple Mini or the PC side. I think you mean Maple Mini. On the PC side, I'm just listening for the stream of data from the Maple. I'm not doing any writes to the device in this mode. The really odd thing is that this is just a problem on windows. Under Linux and Mac, I can read the data stream at full speed. What could be different on the windows side? And is there anything I can do to change it. This seems to be a problem at the windows usb layer.

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RogerClark
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Re: Very slow reading from Maple Mini

Post by RogerClark » Tue Jul 19, 2016 11:07 pm


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