eSATA Oscilliscope - Page 1
Forum section: electronics / projects

author: CM800
author_rank: Frequent Contributor
timestamp: February 23, 2014, 04:19:01 pm
content: Ive been thinking recently.Would it be feasible to have a software/hardware oscilliscope using a high speed ADC and some sort of eSATA converter to transfure the data to the computer, then use software to handle the data?I don't understand that much about these things, but is it a possible idea?

author: Marco
author_rank: Super Contributor
timestamp: February 23, 2014, 04:25:39 pm
content: It's not really worth it, it wouldn't be a lesser complexity project than just hanging high speed DRAM off your FPGA ...

author: cybermaus
author_rank: Frequent Contributor
timestamp: February 23, 2014, 04:32:50 pm
content: In the past the USB speed may have been a theoretically limiting factor for high framerate waveforms.But with USB3 there is no need to go look for a eSATA connection.And frankly, even USB2 with 480Mbps should have been able to deliver 75000 fps on a 800 wide screen, half that if you deduct overhead and comm errors. So I suspect transfer speed is not the bottleneck.

author: CM800
author_rank: Frequent Contributor
timestamp: February 23, 2014, 04:38:02 pm
content: The main idea is to take heavy processing into the computer.Im curious about how much data / channels the average computer could handle and deal with... mabye even some posh signal decoding for digital too

author: Marco
author_rank: Super Contributor
timestamp: February 23, 2014, 04:46:59 pm
content: Quote from: TCWilliamson on February 23, 2014, 04:38:02 pmWhat heavy processing would you want to do on the live data? Complex triggering is hardly heavy processing.

author: CM800
author_rank: Frequent Contributor
timestamp: February 23, 2014, 04:51:47 pm
content: Decoding digital data into its values.Building Graphs and other fancy charts from data live and more or less anything anyone would want.

author: Fsck
author_rank: Super Contributor
timestamp: February 23, 2014, 05:25:51 pm
content: pretty sure using esata is an uphill battle.if you look at the picoscope 6k series, they claim a streaming rate of >150MS/s over USB3 using their SDK but only 10MS/s using their software.high throughput real time data analysis is sort of a problem for computers, which is why this function is typically done through fpga/asic and then that data is fed to a computer for post processing.possibly with a workstation + gpgpu with data streamed over infiniband (low latencyish), or just doing it directly over PCIE3 x16, you may get a decent streaming rate.

author: free_electron
author_rank: Super Contributor
timestamp: February 23, 2014, 05:28:07 pm
content: Quote from: TCWilliamson on February 23, 2014, 04:19:01 pmDon't do that ! bad for you …While it would be possible to do that ( your main problem would be tho make the thing appear as a drive and spit out a file. then the next problem is how do you deal witha file where the data changes continuously ? you would need a massive buffer on the board and rotate between two files. )the big problem is that an ADc is not an oscilloscope ! you are missing input scalers , attenuators , amplifiers, trigger logic and lots of other things.

author: CM800
author_rank: Frequent Contributor
timestamp: February 23, 2014, 06:08:25 pm
content: Quote from: free_electron on February 23, 2014, 05:28:07 pmI must say i feel a bit dumb having forgot all that stuff...Hmm, is there anywhere good i can learn more about this kind of digital electronics and such?

author: Marco
author_rank: Super Contributor
timestamp: February 23, 2014, 08:40:52 pm
content: Ehh, with modern VGAs a front end really isn't that special ... look at the KNJN Flashy boards, add a source follower front end with some decent input protection and you have something which will handle most use cases (leave attenuation to the probe). Triggering can be done in software.

author: mamalala
author_rank: Unknown
timestamp: February 24, 2014, 12:26:26 am
content: Quote from: free_electron on February 23, 2014, 05:28:07 pmNot really. Assuming that the thing can be mounted as a regular drive, and that whatever it is reading from is a regular file, said file only needs to be logically appended to, so that the reading process can see that the file has changed, and subsequently read from it. But even if not, who says it has to appear as a drive? SATA (and SAS) is basically just a high speed serial channel. No need for a real drive or filesystem here. It would be enough for the host to read, lets say, block 0 all over again, and depending on a bit on the first byte of that block deecides wether the data is still the same old, or if something new has arrived.Greetings,Chris

author: Rasz
author_rank: Super Contributor
timestamp: February 24, 2014, 12:50:29 am
content: Even PCIE would be easier than SATA.Not really convenient now that we have usb 3.0. Get yourself Cypress EZ-USB FX3 dev board and start playing. ~250MB/s is easily reachable.That will get you half way there, the other half is frontend.

author: mamalala
author_rank: Unknown
timestamp: February 24, 2014, 01:01:44 am
content: Quote from: Rasz on February 24, 2014, 12:50:29 amSATA, the older spec, has 3 GBit/s. The actual one has 6GBit/s. 8 and 16 GBit/s when using SATA Express with one or two PCIe lanes.The advantage with SATA is that you can use a simple eSATA connector externally. PCIe is quite a bit harder to get externally connected to.Greetings,ChrisEdit: yea, forgot about the really old one, with only 1.5 GBit/s. Still much faster than USB...

author: CM800
author_rank: Frequent Contributor
timestamp: February 24, 2014, 09:27:14 am
content: My main thoughts is that it would be a cool idea to have a computer handled oscilliscope with a lot of the extra cost knocked out but still high-end functionality...Since a PCIE bus is faster.. what about building an oscilliscope onto one or 2 boards? i would have thougth there would be a market for that.

author: amyk
author_rank: Super Contributor
timestamp: February 24, 2014, 12:14:47 pm
content: Quote from: TCWilliamson on February 24, 2014, 09:27:14 amHigh-end oscilloscopes are essentially a regular PC (often running Windows) with data acquisition cards plugged into the mobo. Dave has torn down at least one, check out the videos.

author: krenzo
author_rank: Regular Contributor
timestamp: February 24, 2014, 07:47:00 pm
content: Quote from: TCWilliamson on February 24, 2014, 09:27:14 amWhat extra cost would be knocked out? The majority of the cost is in capturing and digitizing the signal.

author: Rasz
author_rank: Super Contributor
timestamp: February 25, 2014, 12:53:20 am
content: Quote from: krenzo on February 24, 2014, 07:47:00 pmmajority of the cost for manufacturerfor client half of the cost can come from buying software upgrades, protocol decoders etc, basically uncrippling the software stack running the scopeDo you really think half a mil Lecroy scope cost >$20K in parts? Maybe ~40K if they went for the biggest most expensive stratix/virtex.This is why big guys wont do it. It would cut margins and kill golden goose. R&D money needs to come out from somewhere.