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Choosing an Oscilloscope or logic analyzer

amrrahmy

Thanks in advance,

I am familiar with basic multimeters or avo-meters.

I wanted to know what kind of features and speeds, digital or digital and analogue, or which Oscilloscope to get for,

- reading slow-ish serial communication, UART, I2C, SPI, weigand output, at normal micro controller speeds (9600, 19200, 115200), and 3.3v, 5v, and 12v mostly

- no analogue voltage or ADC or sound, but mainly digital communication

I would like to "capture" or set "triggers" for messages coming from a device, maybe transfer it to usb drive or pc, optionally, view it as hex or ascii in Oscilloscope.

Optionally,

- reading output from HDMI 2.1 (48Gbps in bandwidth) or latest display port

- reading output from USBC with alt display port, like between PS5 and PSVR2

From what i have seen advertised, 1-2 channel, 100-200mhz,

  • Real-time sampling rate up to 1 gsa/use
  • IRecord length up to 14 Mpts

How does that equate to bitrate? can something with these specs capture hdmi signal at 48Gbps? would i need more channels for HDMI and USB C with display port?

do i need an adapter to clip onto tiny connectors like usb c and hdmi? a breakout accessory of sorts?

Update:

I was looking to get information about "regular" oscilloscopes in the range of $500-2K.

I see that logic analyzers(for slower speeds) in combination of something like wireshark for usb related packet capturing/monitoring might work better, as an affordable oscilloscope would only work for up to 100Mbps or 200Mbps.

Parents
  • +1

    Scopes capable of HDMI 2.1 or even USB 3.0+ are extremely expensive. You'll be looking well above $50k. Even then, for what you want to do, you probably can't afford the precision cables and test fixtures needed to connect them - or you might have to build your own. Then you'll have to also invest in high-enough bandwidth differential probes - you can't just "connect with a wire". Just having a scope is not enough.

    A 100-200MHz scope is really only usable for relatively low-speed signals by comparison, in part because most low-cost scopes really don't have all that much memory. 14M points is better than nothing, but at 1GSa/s to get nice 200MHz bandwidth captures, that's a capture memory length of 14ms. If you can't trigger on what you want or there is no decoder, then that's potentially extremely limiting. That being said, regular UART could probably be done at about 1-8MSa/s, so you can get a few seconds out of the memory buffer depending on the baud rate.

    If you work purely in digital, a logic analyser may be a better option overall.

    - Gough

Reply
  • +1

    Scopes capable of HDMI 2.1 or even USB 3.0+ are extremely expensive. You'll be looking well above $50k. Even then, for what you want to do, you probably can't afford the precision cables and test fixtures needed to connect them - or you might have to build your own. Then you'll have to also invest in high-enough bandwidth differential probes - you can't just "connect with a wire". Just having a scope is not enough.

    A 100-200MHz scope is really only usable for relatively low-speed signals by comparison, in part because most low-cost scopes really don't have all that much memory. 14M points is better than nothing, but at 1GSa/s to get nice 200MHz bandwidth captures, that's a capture memory length of 14ms. If you can't trigger on what you want or there is no decoder, then that's potentially extremely limiting. That being said, regular UART could probably be done at about 1-8MSa/s, so you can get a few seconds out of the memory buffer depending on the baud rate.

    If you work purely in digital, a logic analyser may be a better option overall.

    - Gough

Children
  • +1 in reply to Gough Lui

    If you're still interested, there are not many USB 3.2-capable oscilloscopes - these would be something like:

    • Keysight Infiniium UXR0164A
    • R&S RTP164B
    • Tektronix MSO / DPO70000

    Plus whatever software options they want for them. There maybe a few more (from Rigol, Teledyne LeCroy) but they're not cheap. Unless you've got a deep knowledge of USB protocols and how to use the equipment, and have the test fixtures, they'll not be of much use to you.

    HDMI 2.1 uses 4x12Gbit/s channels, so you're probably going to want something even better for that ...

    Put it this way - if a signal has a certain bandwidth, whatever you're using to measure it needs to have even more bandwidth than that to accurately capture it. Even then, at such high rates, you're likely only capturing fractions of a second of data for analysis - oscilloscopes don't run continuously like a data-logger for example.

    - Gough

  • 0 in reply to Gough Lui

    OK, that clarifies things a bit, so a 200Mhz is probably suited for 100Mbps bitrate, and usb 3/3.2/lightning/3.2 with displayport/HDMI/displayport are already out of range of a "regular" oscilloscope or logic analyzer.

    The second point I got from the replies, logic analyzers plus a computer would work for digital communication capturing and seem to cost less because they don't include a built in monitor, processing for visualization, and don't include analogue channels.

  • 0 in reply to amrrahmy
    amrrahmy said:
    logic analyzers plus a computer would work for digital communication capturing

    They are more specialised for digital signals that are either 1 or 0 - this includes I2C, SPI. They usually don't work for encoded signals (e.g. Ethernet, HDMI, etc) as they are encoded using a scheme to squeeze more data into the same bandwidth/symbol rate. Many of these aren't intended for very high data rates either ... the average Salae Logic Analyser is only good for 25MHz/100MHz depending on the model for example.

    You will need to read up on the datasheets from the manufacturer to know exactly what each can and can't do ... higher-end products can sometimes be demonstrated by local sales representatives so you can see if it meets your needs.

    - Gough