How many channels do I need to decode any serial interface with oscilloscope?

[caveleira]

Hi, I am considering to buy an oscilloscope for our Company. Not sure yet exactly what for, and nothing too expensive.
What for sure seems interesting is the possibility of Decoding Serial Interfaces. Since 4 Channels is quite more expensive than 2, comes the question, how many channels do I Need? SPI for example uses 4 lines, means that the oscilloscope Needs the four channels attached to decode the data? Makes sense, but is not yet so well informed by the manufacturers. So hope someone can hier clarify me that.
Thanks in advance!

[Kalvin]

You may also consider Saleae Logic-products in addition to the oscilloscope. The Saleae Logic-products are very handy and can really save your day. There might be some other similar products in the market, but I have used the Saleae Logic-devices in my professional life with great success.

[MosherIV]

Most oscilloscopes do not allow you to decode serial interfaces on the analogue channels.
(Some do but you have to check the individual oscilloscope features and then they are software enabled add ons, ie more moeny).

What you are talking about is a Mixed Signal Oscilloscope, where they have 2/4 analogue channels and 8/16/24/32 digital channels.
Again, the serial decode will likely be software enabled add on.

[caveleira]

You may also consider Saleae Logic-products in addition to the oscilloscope. The Saleae Logic-products are very handy and can really save your day. There might be some other similar products in the market, but I have used the Saleae Logic-devices in my professional life with great success.

no thanks, I want all in one Piece

Most oscilloscopes do not allow you to decode serial interfaces on the analogue channels.
(Some do but you have to check the individual oscilloscope features and then they are software enabled add ons, ie more moeny).

What you are talking about is a Mixed Signal Oscilloscope, where they have 2/4 analogue channels and 8/16/24/32 digital channels.
Again, the serial decode will likely be software enabled add on.

well, the ones im looking at, they can decode, and they are not MSO.
Of course Im thinking buying also the Serial decode Software.
The question is still.. can the Software decode with 2 channels, or Need 4.

[dmills]

SPI needs at least 3, and 4 if you want to watch both directions, UART can of course make do with 2 as can I2C.

Regards, Dan.

[Kilrah]

Well obviously you need as many channels as the particular interface you want to decode has lines... so that's only one for one-wire, SPI needs 4 and others may need more.

no thanks, I want all in one Piece

Don't know your reasons, but in most cases a standalone PC-based logic analyzer is more useful than the same feature built in to a scope.

[caveleira]

thank you very much dmills, now is clarified

Well obviously you need as many channels as the particular interface you want to decode has lines... so that's only one for one-wire, SPI needs 4 and others may need more.

no thanks, I want all in one Piece

Don't know your reasons, but in most cases a standalone PC-based logic analyzer is more useful than the same feature built in to a scope.

thanks to you too
PD:because of the work Environment, no PC

[tszaboo]

Get a 4 channel MSO with built in 16 channel Logic analiser. Saleeaeie is a toy, with other USB logic analisers you lose time instead of working.

[MosherIV]

Hi, I am considering to buy an oscilloscope for our Company. Not sure yet exactly what for, and nothing too expensive.
What for sure seems interesting is the possibility of Decoding Serial Interfaces. Since 4 Channels is quite more expensive than 2, comes the question, how many channels do I Need? SPI for example uses 4 lines, means that the oscilloscope Needs the four channels attached to decode the data? Makes sense, but is not yet so well informed by the manufacturers. So hope someone can hier clarify me that.

To decode SPI, you must have 4 channels, you can get away with 3 if you are not bothered about the ChipSelect.

4 Channel DSO are way more expensive than 2 channel ones, probably because the low end 2 channel models are targeted for hobbiests but the 4 channel models are targeted for companies.

A compromised would be a Mixed Signal Oscilloscope with 2 analogue channels and 8/16 digital channels. I do not know if any vendor does one of these today, I have certainly used one that was a HP that was nearly 20 years old. Hopefully, this will be a cheaper option that the 4 channel DSO but I do not know.

[wraper]

Hopefully, this will be a cheaper option that the 4 channel DSO but I do not know.

certainly not

[suicidaleggroll]

PD:because of the work Environment, no PC

You're developing and/or debugging a serial interface and you don't have access to a computer?  How does that work?

I'm struggling to think of an application in which you would need to decode a serial data stream, but you wouldn't have a computer there with which you could actually do something with the information you learn from the LA.

[Aeternam]

A compromised would be a Mixed Signal Oscilloscope with 2 analogue channels and 8/16 digital channels. I do not know if any vendor does one of these today, I have certainly used one that was a HP that was nearly 20 years old. Hopefully, this will be a cheaper option that the 4 channel DSO but I do not know.

The new R&S HMO1002 fits the bill: https://www.rohde-schwarz.com/product/hmo1002-productstartpage_63493-61541.html I believe Dave did review and tear down videos not too long ago.

Be aware though that you'll need (a) the serial bus decode option and (b) the optional digital probe.

[caveleira]

PD:because of the work Environment, no PC

You're developing and/or debugging a serial interface and you don't have access to a computer?  How does that work?

I'm struggling to think of an application in which you would need to decode a serial data stream, but you wouldn't have a computer there with which you could actually do something with the information you learn from the LA.

This should be a multipurpose tool. Sometimes there will be PC, sometimes not.

Thats all about this topic my friends, I already have info from oscilloscopes and so on, thanks for your help. 

[Nozzer]

A compromised would be a Mixed Signal Oscilloscope with 2 analogue channels and 8/16 digital channels. I do not know if any vendor does one of these today, I have certainly used one that was a HP that was nearly 20 years old. Hopefully, this will be a cheaper option that the 4 channel DSO but I do not know.

The new R&S HMO1002 fits the bill: https://www.rohde-schwarz.com/product/hmo1002-productstartpage_63493-61541.html I believe Dave did review and tear down videos not too long ago.

Be aware though that you'll need (a) the serial bus decode option and (b) the optional digital probe.

The newer HMO12nn series offer it too. I was reading their manual (available online) and it suggests that if you buy their full software option you get the 8 digital channels on the POD plus three analogue channels on their two channel scope. Apparently the output for the built-in 25KHz signal generator serves as the third analogue input. This is interesting as the HMO2024 which I was considering and has 4 analogue channels only offers 3 usable analogue channels despite having 4.

[tautech]

well, the ones im looking at, they can decode, and they are not MSO.
Of course Im thinking buying also the Serial decode Software.
The question is still.. can the Software decode with 2 channels, or Need 4.

.
Some protocols do require more than 2 channels and as others have described if you need to see all the related signals you'll want 4.
Additional digital channels to 2 analogue channels in that case may be a cheaper option, the Siglent SDS1000X or plus series with 16 ch La and Decode might interest you.
http://www.siglenteu.com/pdxx.aspx?id=2373&T=2&tid=1
If you drill down into the accessories tab you'll see the LA has a wide flat ribbon cable that can be a little inflexible however ASAIK it can be substituted with an SCPI cable that is more flexible.

A SDS2000X series on the other hand is available in 2 or 4 ch versions and a 16 ch LA option can be added if required, it's a nicer unit with the LA cable, while still a flat cable is split into 2 x 8 channel cables with a detachable pod on the end of each cable that is ~1m long.
The second image in this page gives you an idea of what it looks like:
http://www.siglenteu.com/pdxx.aspx?id=1195&T=2&tid=1
There's some upgrade deals on these ATM that might be worth considering.

There's also the option of using the external trigger input that both these Siglent models provide for a de facto 3rd channel.

[tszaboo]

well, the ones im looking at, they can decode, and they are not MSO.
Of course Im thinking buying also the Serial decode Software.
The question is still.. can the Software decode with 2 channels, or Need 4.

.
Some protocols do require more than 2 channels and as others have described if you need to see all the related signals you'll want 4.
Additional digital channels to 2 analogue channels in that case may be a cheaper option, the Siglent SDS1000X or plus series with 16 ch La and Decode might interest you.
http://www.siglenteu.com/pdxx.aspx?id=2373&T=2&tid=1
If you drill down into the accessories tab you'll see the LA has a wide flat ribbon cable that can be a little inflexible however ASAIK it can be substituted with an SCPI cable that is more flexible.

A SDS2000X series on the other hand is available in 2 or 4 ch versions and a 16 ch LA option can be added if required, it's a nicer unit with the LA cable, while still a flat cable is split into 2 x 8 channel cables with a detachable pod on the end of each cable that is ~1m long.
The second image in this page gives you an idea of what it looks like:
http://www.siglenteu.com/pdxx.aspx?id=1195&T=2&tid=1
There's some upgrade deals on these ATM that might be worth considering.

There's also the option of using the external trigger input that both these Siglent models provide for a de facto 3rd channel.

It is for a company. You dont suggest chinatech scopes for a company. You buy an Agilent, R&S, or LeCroy based on taste, or Tektronics if you are a clueless manager.

[wraper]

As nothing too expensive asked, and likely cannot be cracked as for the company, then 4 ch GW Instek GDS-2000E series 4ch scope might fit. Serial decoders come by default, no options to purchase or crack, everything already there.

[LabSpokane]

Don't know your reasons, but in most cases a standalone PC-based logic analyzer is more useful than the same feature built in to a scope.

Yup. You need the scope when looking for signal integrity issues and the decoded data. For pure decode, a separate device is more useful.

In Keysight's line, it's worth being aware the decoding is supported on the MSO lines on the 3000 series and above scopes. Never mind that the 2000 series has logic probes.

[tautech]

It is for a company. You dont suggest chinatech scopes for a company. You buy an Agilent, R&S, or LeCroy based on taste, or Tektronics if you are a clueless manager.

Tell that to my company customers. 

[vodka]

It is for a company. You dont suggest chinatech scopes for a company. You buy an Agilent, R&S, or LeCroy based on taste, or Tektronics if you are a clueless manager.

I think that the caveleira corporation is a little corporation i doubt that they can spend on expensive instruments as Tektronicks or Agilent

[vodka]

It is for a company. You dont suggest chinatech scopes for a company. You buy an Agilent, R&S, or LeCroy based on taste, or Tektronics if you are a clueless manager.

Tell that to my company customers. 

The problem is that the  Agilent , Lecroys  etc instruments are manufactured in China as the Siglent and Rigol, but 4 or 5 times more expensives.

Now if the  instruments traditional corporation want to sell, they know that they must do.

[JPortici]

chinatech doesn't mean "made in china"
that would be stupid.

[Nozzer]

It is for a company. You dont suggest chinatech scopes for a company. You buy an Agilent, R&S, or LeCroy based on taste, or Tektronics if you are a clueless manager.

Tell that to my company customers. 

The problem is that the  Agilent , Lecroys  etc instruments are manufactured in China as the Siglent and Rigol, but 4 or 5 times more expensives.

Now if the  instruments traditional corporation want to sell, they know that they must do.

The new Rohde and Schwartz are manufactured in the Czech Republic under strict German supervision. The HMO1202 100MHz version sells for under £700 (before tax) in the UK and a little under £1500 for the 300 MHz version. The external digital probe and software will add around an extra £600 to that figure. The downside is that it only offers 10,000 wfs.

[vodka]

The HMO1202 100MHz version sells for under £700 (before tax) in the UK and a little under £1500 for the 300 MHz version.

I see the oscilloscope series HMO1202  prices any low from 1000€ (exclude VAT) . Besides ,i compare among the oficial house and distribuitor and the price are the same

Spanish Rohde
http://shop.rohde-schwarz.com/es/catalogsearch/result/index/?dir=asc&limit=25&order=price&q=hmo

German Rohde
http://shop.rohde-schwarz.com/de/catalogsearch/result/index/?dir=asc&limit=25&order=name&q=HMO

Spanish Farnell

http://es.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15001&langId=-5&storeId=10176&categoryId=700000027009&eq=N%3D220630%26amp%3BNs%3DP_STORE_MARKETING_RANK_FARNELL_ES%257c0%257c%257cP_MAN_PART_NUM%257c0%26amp%3BNtpc%3D1%26amp%3BNtpr%3D1&showResults=true&aa=true&pf=513163562&vw=

And  testing the manufactured place

https://en.wikipedia.org/wiki/Rohde_%26_Schwarz

[danadak]

You said cost was a consideration, then discussed no PC.

If you get a PC, which you need to debug unless you are using stand alone board with
display, these are very low cost, most serial busses -

http://www.ebay.com/itm/24MHz-8-Channel-USB-Logic-Analyzer-8-CH-Logic-Analyzer-for-Arduino-MCU-/191685084604?hash=item2ca15245bc:g:KFYAAOSwyQtV1vOO


Regards, Dana.