To send control data to TAS1020B from PC via USB, one method is to use HID.dll on windows. We found that the latency of sending a small data buffer (about 40 bytes) is around 10ms using HID via control transfer. What is the minimum latency that one can achieve for TAS1020B? Is there a better way to send control data to TAS1020B via USB on PC?
That 10ms latency could originate in HID stack latency on your host PC and/or latency in the 'return' mechanism (which might involve an interrupt endpoint with an 'interval' that is larger than 1ms).
From Windows, I think you could use WinUSB to send control transfers to endpoint 0; perhaps this would result in less latency than using HID (but I haven't actually measured).
If interested, please see http://www.microsoft.com/whdc/connect/usb/winusb_howto.mspx . I used WinUSB in the past to construct a DFU downloader - if you want the source for that please advise.
Can you provide a copy of the source? I would like to give it a try to see how much improvement can be done.
There should be an attached zip file, to which the following refers:
Driver installation:- build your own driver installation package to get WinUSB installed on your PC - obtain the latest Windows Driver Development Kit (WinDDK) from Microsoft (7600.16385.0) - build a 'driver install package' (a directory structure works, but you could burn CD): - dfu.inf [provided in WinUSBTAS1020BDFU.zip] - duf.cat [build this file by running makecat.bat from the zip] - amd64 (directory) - WdfCoInstaller01009.dll (from WinDDK\redist\winusb\amd64 directory) - winusbcoinstaller2.dll (from WinDDK\redist\winusb\amd64 directory) - ia64 (directory) - WdfCoInstaller01009.dll (from WinDDK\redist\winusb\ia64 directory) - winusbcoinstaller2.dll (from WinDDK\redist\winusb\ia64 directory) - x86 (directory) - WdfCoInstaller01009.dll (from WinDDK\redist\winusb\x86 directory) - winusbcoinstaller2.dll (from WinDDK\redist\winusb\x86 directory) - note: dfu.inf and dfu.cat are located in some directory, under which subdirectories 'amd64', 'ia64', and 'x86' have been created, and which hold the two files for the associated architecture from the WinDDK)- attach a TAS1020B having no EEPROM, or blank EEPROM, to your PC- when Windows lets you specify the driver's source location, point it to your directory structure To program a blank EEPROM:- make sure the image file has 'EEPROM overwrite' enabled- unzip 'download.exe' from the zip file- run command 'download <name of image file>'- note that this should program the EEPROM, but will not cause the downloaded image to start running- power-cycle or reboot the TAS1020B
Notes on 'download.exe':- the image file you download must have the header information already prepended- information from the header and TAS1020B is displayed as the download proceeds- download.exe can (and will, if there's no blank EEPROM) write to TAS1020B RAM, but since WinUSB does not provide a mechanism for issuing a bus reset, the TAS1020B will not execute that program.- 'download.exe' doesn't do error recovery - so you may have to reboot the TAS1020B if the download fails- source for download.exe is provided in the zip
Got the zip file. Thanks for the upload.
Have one question: does it mean any PC running this utility needs to have WinDDK installed? Or WinUSB comes with Windows 7/XP, and WinDDK is only for the developers?
> does it mean any PC running this utility needs to have WinDDK installed?
You need WinDDK to build the application that uses the WinUSB driver.
At runtime, the PC that runs the application will need the WinUSB driver installed.
Please read the Microsoft document at http://www.microsoft.com/whdc/connect/usb/winusb_howto.mspx
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