I have also done some stress testing using stress-ng on the system, and found that when the I/O is saturated that this issue also comes up. I am aware that there is a difference between the TTY layer and the general USB layer in the Linux kernel, but I am not sure why usbmon is able to see things that TTY does not.
I am not experienced enough with how Linux handles USB to solve this issue, so I’m not sure how to move from here (although not for lack of trying). These logs appear to show the frames being received without any stalling. Then after the “stall” ends all of the data I expected during the last 0.05 seconds shows up very quickly (faster than 128Hz) and then the data is received as expected.Īs part of my debugging efforts, I used wireshark with usbmon to monitor the frames being received from the ADC. For about 0.05 seconds, I don’t see any data received. For example: Data is received at 128Hz, and then a “stall” happens. I have found an issue where the data seems to stall and then rush in at a later point. I am using ttyUSBx to interact with the ADC. For my purposes this data is time sensitive, so having reasonably accurate timestamps on the 128Hz data is important. The ADC should be providing data at 128Hz, and does so fairly reliably. The Software Distribution contains the AirPcap Windows driver, Installation and User's Guides, the Wireshark Network Analyzer, and a collection of developer resources for users interested in including wireless capture directly into their applications.I am working on developing a sensor platform based on a raspberry pi running raspbian and an analog/digital converter (ADC) connected via USB. The AirPcap Nx product includes the AirPcap USB 2.0 adapter and the AirPcap Software Distribution. The AirPcap Nx USB adapter comes with two 2.4GHz 5dBi antennas, two MC-Card to SMA cable assemblies and the AirPcap driver. This unique, dual-band device supports 802.11n, 802.11a/b/g legacy modes, and 4.9 GHz US Public safety channels and offers full Wireshark integration, 2 x 2 MIMO, two internal antennas and two integrated MC-Card connectors for optional external antennas to enhance performance in the most demanding environments.ĪirPcap Nx adapters are easily run under VMWare on a Macintosh or Linux machine (or a VM session within Windows). AirPcap-Nx is end of life (EOL) with no direct replacement.ĪirPcap Nx, an optimized USB-based capture and injection device for Windows platforms, delivers complete visibility into 802.11a/b/g/n wireless networks and guarantees superior capture performance with minimal packet loss, especially when doing multi-channel capture on 802.11n networks.
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