[wdmaudiodev] MIDI SYSEX response lost

  • From: Timothy Knudtson <tknudtson@xxxxxxxxxxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Fri, 23 Aug 2013 12:00:06 -0600

Our company is working on MIDI devices that are configured using SYSEX 
messages. I am seeing a weird behavior with Windows 7 and Windows 8. I send 
5-10 SYSEX messages to the device and receive the expected responses, then for 
the next 20-300 messages the responses do not come back. After sending those 
20-300 SYSEX messages the response start coming in. I have placed a Beagle (USB 
logger) on the line and setup USB logging in windows. From what I see the 
responses are being sent from the device. The response size of the SYSEX 
messages is less than 128 bytes (around 50 bytes on average). I have tried 
using the WindowsMM libraries and the KS libraries and they both exhibit the 
same behavior. My felling is that the issue lies in the USBAudio.sys driver.

This device works on Windows XP, Mac, and iOS. I have not tested on any other 

Any help would be appreciated. Thank you.

Timothy Knudtson

Other related posts: