Products > Test Equipment
Benchmarking GPIB
dragon5:
I wonder if there is a GPIB benchmarking methodology similar to RFC2544 for network interconnect devices that can be used to characterize the performance of a GPIB device.
How do I compare the linux-gpib bitbang driver performance to the proprietary solutions?
I get up to 80 KBytes/s download speed when I download waveforms from Yokogawa DL1540L with the linux-gpib bitbang driver over wireless network ( https://www.hackster.io/lightside-instruments/wireless-lan-gpib-gateway-with-open-source-hardware-6e0af8 ). How do I know if the bottleneck is the oscilloscope or the adapter?
colorado.rob:
Networking is easier because it typically uses fairly symmetric protocols. GPIB is asymmetrical. You would need to have some sort of test device that could sink and source GPIB data at the theoretical max rate, and report on the throughput of the host.
dragon5:
Yes. But how difficult is to connect any FPGA to the 16 bit GPIB connector and make this reference devices that only source and sink traffic at optimal speed?
coromonadalix:
for 1 device it could be possible but many instruments on the gpib may give you different values / timings, if you mix oldies vs new stuff
some of them require specific commands who can slow your gpib system(s) different brands are not equal
better use network when possible, but once again having an 100mb 1Gb line doesn't mean the instrument will spit values faster ...
pqass:
As others have said, the source of the bus data is usually the limiting factor (eg. ADC speed).
As for the bus itself, GPIB is basically a TTL-level bus (48mA line drivers) at most 15m long without terminators and with open collector handshaking lines (DAV, NRFD, NDAC). You can drive it as fast as the peer can stand (it's asynchronous) until bad data creeps in (due to capacitance, reflection, etc. affecting line quality). To mitigate errors, intentionally limiting the data rate is all there is unless each peer implements a CRC as part of their data exchange.
Higher powers have decided that given the topology, the maximum data rate should be 1MB/s in standard mode or 8MB/s in high-speed mode (according to this). FYI: see page 13 for the handshaking protocol explained.
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