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#TIL TI MSP430 CPU's instruction set is basically "what if we redesign the PDP-11, but more RISC-like."
Wow, I spent a month on PDP-11 assembly this year, who knows it has practical applications?! Shut up and take my money? #electronics#retrocomputing#PDP11#MSP430
Just found a good way to photograph and reverse engineer small PCBs - a copy stand. Image quality has dramatically improved compared to the previous attempt. Recent smartphones should also work with a mount adapter if you don't have a camera. #electronics
The result from the flatbed scanner looks good but the focus and resolution are still not good enough for reverse engineering. I need to try again with a camera. #electronics
Adding copper fills and stitching hundreds of vias to ground is always the most satisfying step in PCB routing. "Never trust a copper fill's opinion unless it's well grounded," #electronics
Low-noise DCDC converter is a success. 🎉 The buck converter's output noise is 8.2 mV peak to peak, and noise after the post filter is less than 1 mV, undetectable on this oscilloscope, it's under the noise floor.
I even appear to "beat" the published results by National/TI by not having any switching spikes. Though, I don't think it's because my layout is better, more likely my SMA test ports with full 50-ohm signal paths simply have less measurement artifacts than the banana plugs on the official reference design. #electronics
My circuit board arrived. I found a stupid bug immediately: the 3.3 V power supply could not turn on - there was no ENABLE signal whatsoever, but the pull-up resistor for ENABLE is right there, why?
Then I noticed the ENABLE signal is pulled up to... 3.3 V. :blobfacepalm: 🤣 #electronics
The SFP+ power supply specification is the most convoluted standard I've seen so far. First, your power supply, preferably, should use a reference LC filter. Then you take a measurement at the output side the PSU. Finally you import the data to your computer and divide the results by the transfer function H(f) of that LC filter to deembed that filter and reconstruct the noise voltage before the reference filter.
/me starts hunting for another forbidden USB ASIC you cannot buy - Norelsys NS1021. This chip can transparently convert the USB 2.0 electrical signals to a true AC-balanced form for transmission over CAT-6 or coax cable, with capacitor or transformer isolation.
Not sure if I can use it. There's nothing you can't get from Shenzhen with enough persistence, but getting a leaked datasheet is more difficult...
Found vintage #Tektronix sampling oscilloscope online with 20 GHz sampling + TDR modules installed at a great price. 🤓 But the screen in the photo actually displays a self-test failure :oh_no: Can either be a module fault (replaceable) or a mainframe fault (can be impossible to fix), let's see if I can convince the seller to do some tests... #electronics
Continue my hunt of old test equipment above 1 GHz. Last week I ordered a similar Tektronix sampling oscilloscope from another seller, but it's still not shipped yet. I'm not sure whether the vendor wants to sell it at this point... :blobshrug: Finding a cheap one is the exception rather than the rule (*), but I'll continue searching for them... #electronics
(*) unless you live in the Silicon Valley or near the MIT, both locations have the biggest electronic flea markets in the U.S., you can find a lot of unusual equipment there...
Sad ending. The vendor said the oscilloscope I wanted was listed online for a long time without any buyer, so it has already been completely dismantled by the company for parts. :oh_no: RIP, scope. Tektronix CSA803 & 11801 were the best engineered sampling oscilloscopes from the early 1990s. #electronics
Too bad that a vintage 20 GHz oscilloscope is still unable to do any USB 3.0 testing because there's no clock recovery, and you CANNOT trigger the scope from an external clock either because USB uses spread spectrum clock. The best thing it can do is TDR, which should be good enough, but still leaves a lot to be desired. The brutal reality of high-speed digital systems - $30,000 test equipment needed to verify a $10 disposable computer gadget. #electronics#usb