FlexControl hysteresis problem

The issue is most probably command queuing coming from the FlexControl. As you rotate the knob, the shaft encoder switches opens and closes, sending three byte commands down the USB/Serial connection to the PC which then formulates an appropriate FlexLib command that is set to the radio to tune the radio X number of tune steps in a particular direction. There is also an acceleration algorithm that senses when you are turning the knob faster and informs the radio to execute multiple tuning increments in one radio tuning operation. So as the commands are being sent to the radio, the serial/USB interface has a FIFO buffer that queues these three byte serial command data. If you are rotating the knob at a moderate rate, this buffer will queue commands, so that when the knob stops sending data, there is still data in the queue that gets processed. In addition, if you are rotating the knob at a moderate to fast the acceleration algorithm in in play so when you stop rotating the knob in one direction, the amount of frequency changes the radio executes as the FIFO command buffer flushes will be greater, amplifying the effect you are seeing. So, what can you do to mitigate this? One option is to change the size of the com port FIFO buffer to a smaller size. The following HelpDesk article is PowerSDR specific, so just do step 2 ( http://helpdesk.flexradio.com/entries/22185687-How-to-Mitigate-FlexControl-Latency) If this does not help, the other issue could be the USB interface the FlexControl is plugged into. It is is sharing a controller with other devices, like a mouse, keyboard or printer that can effect the data rate. You can try connecting the FlexControl to a different USB port when SmartSDR is not running.

BIG GRIN :-)