pastro
Junior Member level 3
Hi all,
I have 10 local data collection nodes, all spread a distance of 20ft from a single USB2.0 controller board. Upon formation of a global trigger condition, I have to fill a FIFO on the controller board with 31 words (16 bit = 1 word) of data from each of the 10 nodes in a time of less than 50us. At this point, there exists no FPGA/microcontroller to read out these nodes--just the 10 nodes with 16bit ADCs interfacing to the rest of the world through a 16 pin data bus, plus 26 address/control lines to choose which ADC to readout.
I'm faced with many choices, but the big one I'm stuck on right now is as follows:
given the combination to tight time constraints and long distance, is there a problem with running a very wide (say, a 50 pin bus, so 100 conductor) LVDS ribbon cable at a rate of 6MHz over a distance of 20ft? The large number of conductors is not really a problem. I'm simply asking if you WERE to implement such a 100 conductor LVDS parallel scheme, could it handle a 6MHz rate over a distance of 20ft, or would it be besieged by EMI issues? Has anyone ever attempted such a feet successfully before? What sort of EMI environment were you in when you did it?
The other option is to serialize the bus, but that means running at higher speeds and adding complexity and power to the system...
I have 10 local data collection nodes, all spread a distance of 20ft from a single USB2.0 controller board. Upon formation of a global trigger condition, I have to fill a FIFO on the controller board with 31 words (16 bit = 1 word) of data from each of the 10 nodes in a time of less than 50us. At this point, there exists no FPGA/microcontroller to read out these nodes--just the 10 nodes with 16bit ADCs interfacing to the rest of the world through a 16 pin data bus, plus 26 address/control lines to choose which ADC to readout.
I'm faced with many choices, but the big one I'm stuck on right now is as follows:
given the combination to tight time constraints and long distance, is there a problem with running a very wide (say, a 50 pin bus, so 100 conductor) LVDS ribbon cable at a rate of 6MHz over a distance of 20ft? The large number of conductors is not really a problem. I'm simply asking if you WERE to implement such a 100 conductor LVDS parallel scheme, could it handle a 6MHz rate over a distance of 20ft, or would it be besieged by EMI issues? Has anyone ever attempted such a feet successfully before? What sort of EMI environment were you in when you did it?
The other option is to serialize the bus, but that means running at higher speeds and adding complexity and power to the system...
