Products > Test Equipment
Picoscope Hack
MrAl:
--- Quote from: voltsandjolts on November 26, 2022, 03:44:48 pm ---Did you try figuring out the checksum algorithm at all? The sigrok page you pointed to hints at its workings:
--- Quote --- There is a checksum, but is very weak and overly complicated. The last two bytes contain the number of iterations that have to be done to a 14 bit LFSR to get a value that equals the sum of the preceding data when interpreted as signed bytes. The weakness comes from their method of reducing the sum to 14 bits: During summing they reset the intermediate value to zero as soon as it uses more than 14 bits. As the bytes added are signed, this happens very often.
--- End quote ---
Not sure how they worked that out.
Don't think I've never seen LFSR used as a checksum method...ahh, well I suppose crc is an LFSR method.
There is another picotech device that interests me but the checksum there is a PITA. It might be the same as this one.
--- End quote ---
Yes it's an interesting idea to use the LFSR as part of a checksum. It generates a pseudo random number but with the same seed all the time the sequence will repeat, and thus you can always recreate the sequence if you know the seed.
Since the result of the LFSR is not very related to the input, it's interesting in that even with a string of 0's we'll get full register length outputs. That kinda makes the sum more unique. That's basically how CRC works too.
Basically CRC looks at the bytes and produces a result that is dependent on all the bytes in the sequence, and if any bytes change the chance of generating the same result is very small, so the result pseudo represents a unique values for a set of unique bytes. I would think that would be better than any simple checksum although the calculation is more costly time wise.
markone:
--- Quote from: tautech on December 05, 2022, 09:57:32 am ----snip
IIRC you required triggering on a specific bit, is that still the case ?
Been pretty busy getting newly arrived product out so only getting to touch base with you now.
--- End quote ---
Not on this specific case, i.e. Picoscope 6/7 do not support trigger on serial content, it's enough to react to a falling edge (first byte start bit) to let start the capture segment / serial decoding.
Of course a feature like that would be a nice addition.
_Wim_:
--- Quote from: markone on December 04, 2022, 09:35:47 pm ---Just out of curiosity : how much you paid your Pico and which cost difference there is with your "upgraded" model ?
--- End quote ---
I paid around 1.100€ ex. VAT, but I do not remember exactly what the highend model price was, but would estimate around 1700€? Off course, my upgraded version is not a "full" 5444B, I was mainly interest in the FFT extension (even if it had high frequency roll-off).
markone:
--- Quote from: _Wim_ on December 05, 2022, 06:24:34 pm ---
--- Quote from: markone on December 04, 2022, 09:35:47 pm ---Just out of curiosity : how much you paid your Pico and which cost difference there is with your "upgraded" model ?
--- End quote ---
I paid around 1.100€ ex. VAT, but I do not remember exactly what the highend model price was, but would estimate around 1700€? Off course, my upgraded version is not a "full" 5444B, I was mainly interest in the FFT extension (even if it had high frequency roll-off).
--- End quote ---
So you confirm that prices "went crazy" lately, right now this model cost much more, I guess you wouldn't have bought it at 1500-1600 plus taxes.
In my opinion current listing is no more justified, especially considering that now desktop DSOs are equipped with much more memory compared to the past and 12bits models are much cheaper.
In addition Picoscope 6 starts to be outdated, version 7 is far to be complete or stable and very few people are able (or have time) to develop custom application with SDK library.
_Wim_:
--- Quote from: markone on December 05, 2022, 07:00:20 pm ---So you confirm that prices "went crazy" lately, right now this model cost much more, I guess you wouldn't have bought it at 1500-1600 plus taxes.
--- End quote ---
I do not know. Back then (2017) there were not too many options for a 12bit scope, and the Picoscope was the (the only?) affordable option (and the fact that I already was a Picoscope user).
Today I would probably buy the 12 bit Siglent or Rigol.
As to the price I paid, there was also some price reduction as the follow up for the A/B series was coming to the market, so back then this model was also more expensive. If you compare Picoscope with Tek, Keysight and R&S, their pricing is still quite reasonable. But if you look at Siglent & Rigol, they cannot beat that kind of value for money, but they never could.
Their value has always been in the software, and this is in my opinion were lately they have not made much progress unfortunately. Picosoft 7 is indeed quite buggy, and development on Picoscope 6 has halted for >3 years (apart from the introduction of some new modules and bugfixes).
Still, it is my goto scope for analog work, and I certainly do not regret having bought it.
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