Hi, I’m triggering a pin (or all pins) of the digital output of the K8055 to create a sync. source (say, 10 Hz low percentage duty cycle square wave) via a loop and timer using visual C++ code. I’d expect the output of the K8055 to match the rate at which the C++ loop is executed. However, i notice there is an 8 ms jitter at the output of the K8055 for when the digital output is executed. Is this due to the K8055 clock, USB polling or some sort of buffer delay in the K8055… Is there anyway to get a stable output? Does anyone else have experience with this… Would i best be best to directly programme the computers parallel port instead to achieve stable clock rates? Any boards that do not suffer this affect? Thanks in advance.
The USB sends the commands to the K8055 card at the rate about 8ms per command. This limit is determined by the USB latency (max. 10ms). That is the reason to the jitter.
Many thanks for the prompt response, i was suspecting this was the case and appreciate having it confirmed. BTW, the board is otherwise a fantastic bit of kit! I plan to try inpout32.dll with the parallel port for my particular application, hopefully this will remedy the problem. I’m also aware that you have a faster USB board with a lower latency should anyone else only need to double the BW (half the latency).
Yes, the K8061 is faster. The latency time is about 2ms.
It may be difficult to access the parallel port.
I have no experience of the inpout32.dll.
One alternative to get access to the parallel port is using the DLPORTIO.DLL and DLPORTIO.SYS.