Products > Test Equipment
Picoscope Hack
_Wim_:
--- Quote from: voltsandjolts on November 26, 2022, 02:02:44 pm ---Nice!
Dave did a teardown of this scope a few years back, but didn't open up the front end cans.
youtu.be/TM7HGFOc74M?t=351
--- End quote ---
Thanks. I watched that one. It is also the version with the protocol analyzer, and hence has a different board layout. It does however not have any unpopulated chips in contrast to mine, so those unpopulated sections will probably be the culprit for some of the remaining "issues".
voltsandjolts:
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.
_Wim_:
--- Quote from: voltsandjolts on November 26, 2022, 03:44:48 pm ---Did you try figuring out the checksum algorithm at all?
--- End quote ---
No, I did not. As the Sigrok paged showed bytes were summed and the checksum was just the position in the LFSR series that matches the sum, I just ensured the sum would not change by altering the serial number... I briefly thought about programming a generator in C#, but as my trick appeared to work, I did not invest any additional time in this.
--- Quote from: voltsandjolts on November 26, 2022, 03:44:48 pm ---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.
--- End quote ---
I have also no idea how they found that out, that would have been certainly far beyond my skills!
_Wim_:
To fix the memory, I would need to change the memory chip which I consider too risky.
My board has a D9MNJ Micron Technologie (DDR3 SDRAM 1G-Bit 64Mx16), so that would mean max 128M samples @8bit, and I suspect that in 12bit mode they just half the amount of samples and leave those 4-bits unused. Remark: the 5444B from Dave's review had a D9SHD (256Mx16).
This explains why I start to see glitches going above 100MS, and no software hack will be able to fix this...
_Wim_:
Rise time measurements (which confirms the 200Mhz bandwidth)
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