Release 1.729
Pre-release
After installing this version, please re-plug the QA401 to ensure the FPGA is updated!
This is a quick-fix to address the issue on some units with the attenuator cycling forever. The symptom is that you run the program, plug in the QA401, wait for it to configure, and then disable the attenuator. At that point, the attenuator will cycle on and off forever.
Originally we couldn't duplicate the issue here at all, but today we found a unit that exhibited the behavior. What is looks like is happening is the relay response times are a bit uneven. The attenuator consists of two relays, one for the right channel and one for the left channel. If the relays are perfectly matched, then they both click open and closed at the exact same time. If they are not, then one goes first, and a millisecond or two later, then next one clicks.
The detection logic assumed they both clicked at the same time, but thus there was a single overflow event from the ADC--this event is what drives the overflow detection logic.
But if the relays aren't perfectly matched, then you see the OVF go high while the first channel changes state, and then you see the OVF go high again a short time later.
What is interesting is that you can hear this--on some units, engaging the attenuator sounds like a single click. On a problem unit, you will hear a click-click, separated by a mS or two in time.
The problem may be exacerbated by low USB voltages. In other words, if you are using a USB cable with 26 or 28 AWG power conductors, the response time could worse as the voltage driving the relay is low.
In any case, there is no reason to install this version unless you are having trouble with the endless atten cycling.