From: Harold Hallikainen <harold@mai.hallikainen.org>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Fri, 2 Oct 2020 13:36:23 -0700
Subject: Re: [EE] RS-485 analyzer/sniffer?
Thread-Topic: [EE] RS-485 analyzer/sniffer?
Thread-Index: AdaY/Trov/UY+Ja2SUi3jU1Ccx1nDA==
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This reminds me of a project in the 1980s where I used the Centronics
printer port on a Cromemco CP/M computer as a logic analyzer to reverse
engineer the serial bus for the Commodore 1541 disk drive. For that, I did
a simple transition capture. If any bit changed, I captured the full 8
bits. I did not care about timing. That ended up in this product:
http://bh.hallikainen.org//wiki/uploads/HfDrc190.pdf

Harold


> Disclaimer: This may or may not be a controversial statement.  I'd
> recommend one of the super cheap ($10ish) Salae (sp?) clones.  They do 8
> channels at up to 24MHZ, no serious input protection or fancy probe
> connectors, just raw IDC pins.  You might want to put some blocking
> resistors to limit input current, depending upon the voltages you
> anticipate.  You'd have to verify, but I think the pins can survive + or =
-
> 20V, I just don't remember.  If you burn out a channel, who cares, rig up
> something to protect the ones left.  ;) Buy them by the dozen and throw
> one
> in every toolbox.  But you don't have to use a $10 clone of an ancient
> analyzer, it works with all kinds of analyzers.
>
> I don't recommend using official Salae software, but Sigrok Pulseview
> instead.  It runs in Windows or Linux, there's even an Android app.  I've
> only tinkered with a bit, but I think it's pretty awesome for open source
> software.  There's a jillian "stackable" protocol decoders built in.  It'=
s
> awesome, seriously.  It "knows" the various UART, I2C and SPI protocols t=
o
> talk to a plethora of various chips.  The wiki write up on Sigrok
> Pulseview
> is very detailed.
>
> When I said stackable, that's what I meant, it's nice to look at I2C comm=
s
> and not have to have a datasheet in hand for an ADC or some other IC
> that's
> on the bus, trying to figure out what's going wrong.  Just take a look at
> this list: https://sigrok.org/wiki/Protocol_decoders  It even flags
> missing
> acks, parity or framing errors.  Did I mention that it's awesome?
>
>
> I'm still waiting for a Rigol scope, or any affordable scope, to embed
> this
> ability into their serial decoder functionality.  Pulseview can even talk
> to oscilloscopes; it's not just limited to logic analyzers.  You can
> capture analog signals, convert them to digital day streams (using
> thresholds of your choice) and feed them into the protocol analyzers.
>
> I even use Pulseview with my Hantek 6022bl, it's got a nicer interface.
> Capturing analog inputs and automatically converting them to a logic
> stream
> comes in handy. It can even guess at baud rates, if you're unsure.  It ca=
n
> do timing analysis.  I don't know what else it can do, but there's
> probably
> more.  Be forewarned, capturing at 24MHZ from an unbuffered clone device
> requires a decent computer and a good USB cable, but it works.  You can
> record as many samples as you want, as long as the PC can keep up
> transferring 24 megabytes per second.  The clones seem to sample all 8
> inputs, whether you need them or not.  It's $10, what can you expect.
>
> Here's on for $9, but mine is by hiletgo and cost $12 for the "kit".  It
> looks just like this one.  As long as you don't use Salea software, no
> crime has occurred, nobody was harmed in any way, just a reappropriated
> USB
> VID and PID.  It's certainly not the same quality hardware as the origina=
l
> version.
>
> https://www.amazon.com/Comidox-Analyzer-Device-Channel-Arduino/dp/B07KW44=
5DJ/ref=3Dasc_df_B07KW445DJ/?tag=3Dhyprod-20&linkCode=3Ddf0&hvadid=3D366289=
581070&hvpos=3D&hvnetw=3Dg&hvrand=3D2425961148164562015&hvpone=3D&hvptwo=3D=
&hvqmt=3D&hvdev=3Dm&hvdvcmdl=3D&hvlocint=3D&hvlocphy=3D9052205&hvtargid=3Dp=
la-804742835968&psc=3D1&tag=3D&ref=3D&adgrpid=3D71490160010&hvpone=3D&hvptw=
o=3D&hvadid=3D366289581070&hvpos=3D&hvnetw=3Dg&hvrand=3D2425961148164562015=
&hvqmt=3D&hvdev=3Dm&hvdvcmdl=3D&hvlocint=3D&hvlocphy=3D9052205&hvtargid=3Dp=
la-804742835968
>
>
> On Thu, Oct 1, 2020, 15:38 mbaum7901 <mbaum7901@gmail.com> wrote:
>
>> I have used a free software package called TAL Breakout for over 15
>> years.
>> It is actually a demo of a commercial offering, but the free version
>> works
>> very well
>>
>> https://www.taltech.com/blog/post/tal_breakout_software_freeware
>>
>>
>> -----Original Message-----
>> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
>> Of
>> Harold Hallikainen
>> Sent: Thursday, October 01, 2020 15:04
>> To: Microcontroller discussion list - Public. <piclist@mit.edu>
>> Subject: Re: [EE] RS-485 analyzer/sniffer?
>>
>> I've used a logic analyzer like the thech-tools DigiView to watch a 485
>> bus
>> directly. No 485 receiver required since one wire or the other is 5V
>> serial
>> data. Also, RealTerm can capture serial data and display it in hex.
>> I use an FTDI TTL-232R-5V-WE cable to get TTL or similar level data into
>> a
>> USB comm port.
>>
>> Harold
>>
>>
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