Choosing an Oscilloscope or logic analyzer

If you want to just look at digital signals and comm. protocols, you need a mixed signal scope or maybe a digital logic analyzer. There are few scopes from Keysight which have some add-on modules for decoding comm. protocols but a dedicated analyser is the best solution.

You don't mention your budget but you won't get a scope capable of direct connection to HDMI (the 4.9Gbit part) under $50k. You'll need 16GHz scope bandwidth and matching differential probes.

Unlesss you are doing something very odd you would be better off with an HDMI analyser but it won't be cheap.

USBC at ultra speed  - same applies.

For the low speed stuff I'd suggest a Picoscope - you get lots of decoders in the basic price and the scope parts work well. You'll need 4 channels and/or one with a logic analyser.

You might get away with a logic analyser  - I can recomend the ones from ZeroPlus which I own and use. There are others. It can be very difficult to debug serial prootocols without a real scope - signal integrity problems are common and the best an analyser can do is tell you that there is a problem - it won't help you work out what it is.

All the major scope manufacturers offer mixed signal scopes with protocol decoders at various prices.

If you budget is very tight then go for a logic analyser using open source software (Sigrok) and a cheap scope if you end up needing it.

MK

ok, so, the oscilloscopes that costs $500-2K are for slow speed communication, something with logic analyzer will have multiple wires/channels.

for usb I can potentially use wireshark if there are no drivers in windows or linux, and that might work for usb 3/3.2/usb with display port/usb with lightning, doesn't matter?

I assume if i use libusb (usb protocol)  or libusbk, which i used before for usb 2.0 devices, which is old, without device drivers, I might still be able to make a program to capture data over usb 3.2 with display port or usb with lightning?

and this will not work with highspeed stuff like usb 3.2 or hdmi?

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

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

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.

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