Anybody know if the RS232 to USB adaptor buffers?

lboucher

Hi All

I am running 1 way serial thru the Parallax RS232 to USB device.
57600 baud.

I am using it to control christmas lights.

Interestingly i can unplug the USB from the computer and the christmas lights keep flashing for 2-3 seconds.

So it appears it is lagging/buffering for 2-3 seconds.
Anybody experience anything like this?
Any suggestions?
Do all serial to USB devices do this or will others work better?

Lucas

--EDIT

Nevermind, my mistake.
I was using a random blink pattern for my test.
Further tests with ramps reveal that there is no buffer but plugging in/unplugging the rs232-usb sets off random channels.
Noise i guess?

Post Edited (lboucher) : 9/6/2009 4:15:41 AM GMT

Mike Green

All USB to serial adapters buffer their data. The effect of this is called latency and the amount of latency is sometimes adjustable. I believe the Windows drivers allow this to be adjusted. USB can transfer data much faster than the usual Baud used by most adapters (typically 2400 to 38400 Baud) and the buffers in the operating system and in the adapter are used to try to smooth out the flow of data.