Hellooooo #VCFMW!
Remote
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@bytex64@awesome.garden
hometown 4.5.10+hometown-1.2.1Professional hacker. Amateur artist. Hobbyist ne'er-do-well.
584 Followers
190 Following
50 Posts
Joined December 28, 2022
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This dissected mouse is a Logitech M-BD58, one of the first popular optical mice from around the turn of the century. If you're over 30, you've probably seen one. The other mouse is a M-BJ58, which looks identical. Clearly one is a later version of the other, but I don't know which.
Boosted by @GroupNebula563@mastodon.social
In other shenanigans, did I melt a PLA cup into a plastic puck on the stove? Yes. Did it become irrevocably fused to the aluminum? Also yes.
(And shout out to Loaves and Witches, they’re awesome)
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But I have made another mistake that helps here. I went to order more solder braid and didn’t think about the size, I just got the smallest one I could find. Last time that was 2.5mm. This time it was 1.5mm. Which is almost unusably small unless you’re cleaning up things like this.
Some wick, tacky flux, and drag soldering, and it looks much better.
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IT LIVES!
It needs the display connected to boot, and it’s making an annoying whine. But this is a working system!
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For short bodges like this, I like to strip piece of wire and use the wire itself as a handle when soldering. Then bend it where it needs to go, solder, then cut off the rest of the wire. This went pretty smoothly, thankfully.
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@NanoRaptor@bitbang.social Probably ~$21K? They made us memorize either the Gettysburg Address or “O Captain My Captain” in eighth grade. I chose Gettysburg and I think I’d probably get to “dedicated” before I bunged it up.
Alternatively, I can recite all the words to Mr Weebl’s “Badgers” and it doesn’t ever end. So if that counts… infinite money?
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I just removed the load caps, and it completely fixed it. Rock solid now, even at the usual SPI flash clock divisor (2).
I'm not sure I've used this footprint with a full ground flood front and back before. I guess those wings for the SMD HC49 are providing the needed load capacitance? Now there's a fun PCB hack. 😆
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I think that’s everything I need to test the RP2040. For some reason when I designed this, I thought I had 27 ohm resistors in 0603. I don’t. So I’ve just bridged them. It’s in the USB 2 data path, it’s probably okay.
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Finally getting back to the MFM emulator. Let’s do some hot plate work!
What’s my paste technique? “Uh, just put that anywhere.”
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#*%$@! I wired the CC pins into the SBU pins. This is going to be an annoying bodge.
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Some of you may be asking, “how on earth do you see those pins, let alone get an iron on them?” You don’t. At this size, you load them up with flux, put a blob of solder on your iron tip, and pray to the chemistry gods that your flux and solder mask keep the solder where it’s supposed to go. I just slowly drag that blob down one edge and check it with a loupe afterwards. I use a meter to check shorts at the other end of these traces, and I have a program that strobes each GPIO to make sure they’re all connected.
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There is, predictably, a reason you don’t do this. Unless you get really good at micro-metering the paste, you tend to make a mess that takes you almost as long to clean up as doing it manually.
It does look like the RP2040 self-centered just fine, though.
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So I could track down a proper power supply or an adapter for this huge barrel jack. Orrrrr I could just replace the jack with a modern 5.5mm jack. It’s rated for 24V 5A, it’ll work fine. And it’s fully reversible.
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Well that sounds more promising. The T1200 does give up on it after a bit and continue now, so I’m guessing this is just no data found. Time to find a low level format tool.
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The load capacitance of this Würth crystal is 15pF, so 22pF is a lot closer to what I need. And I have those… in 0805.
Thankfully we’ve got extra pads to work with. Footprints are just like, an idea, man.
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Slapped a Winbond chip on it, let’s see how that does.
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Oh right. This isn't designed to run from flash. It runs from RAM so I don't need to have the flash installed. It's been a while since I've used this.
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I built a little rig to test this thing manually. Buttons for drive select, head select, direction, and step. LEDs to indicate ready, track 0, seek complete, index, write fault, and servo gate. And one extra line for the read pin.
I spent some time tracking down things plugged into the wrong pins, but it didn't seem to show any problems with the device itself. Polarities look right, track 0 behavior is right, seek complete works right, index pulse looks right, servo gate looks right. So yeah, maybe a better cable will fix it. 🤷♂️
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Built the software without too much drama (what compiler defines ulong by default?), and loaded it up. There are no instructions on what the hard drive image needs to be, so I trial and errored my way through that. And when it appeared to load the image and work properly, I got a whole lot of nothing.
Then I thought about it for a second, realized that this thing works on raw flux streams, and I fed it a file full of zeroes. I rewrote the image with random data and voila! Garbage in, garbage out.
Oh also I wired up the STEP pin and the piezo clicker works. :D
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The tool is pretty simple. It outputs N+1 pulses on GPIO N. You check every pin in sequence, counting up one by one.
All pins tested good. 👍
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@thevhswizard@retro.pizza @cohentheblue@ohai.social @evedazzle@mas.to Except for the things that go bad with age or exposure instead of use, like anything made out of polymers (bushings, trim, adhesives, etc). My car is 13 years old but only has 87K miles. Lots of stuff has gone bad anyway. :/ (of course, it’s a Fiat-Chrysler so it wasn’t ever designed to last to begin with)
Also oil does degrade over time. That’s why oil changes list time and mileage recommendations. Modern synthetics are very good, but three years is probably pushing it.
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Oh god I am so relieved. I thought I had bought a brick. I need a more stout power supply to get this running properly, but this is such a win.
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@xgranade@wandering.shop This is a conclusion I came to as well. An “oh no” moment when pondering the nature of slurping down content and making yourself the intermediary. Search engines have already been there for ages, and maybe we should not have given them that power.
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It appears to be attempting to find track 0 by seeking repeatedly. But it’s stuck.
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Yes, I have forgotten to get 100 ohm 1210 resistors for two orders now. :/
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Hm. According to some calculators I'm finding online, these patches should be around 0.25pF, so I probably just got lucky (OTOH maybe the parallel plate model doesn't work with plates this small). I'll find the proper load caps and see how that goes.
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Hm. Test program isn't working. Looks like it starts to access flash, then stops. External oscillator never starts up.
This is a newer flash chip (AT25SF128A instead of the usual W25Q080). I wonder if I compiled this with an old enough SDK that it doesn't know about it.
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Oh, another tidbit I forgot to mention. The keyboard appears to be ALPS or ALPS-like? That’s not a switch I recognize, but it sure looks like a slimmed down SKCM.
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@nina_kali_nina@tech.lgbt @peterbrown@mastodon.scot I did some research on this myself lately, specifically for measuring IR transmittance of window films. The “ceramic” films were shockingly effective compared to regular metallized films. I wonder if that’s what they’re using.
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Part of the problem might be that the drive end of the cable is a slimline version that doesn’t actually fit well into this standard jack (I had to clip out some bits to get it this far). So maybe some signals are just not connecting properly. I’ve also got a male IDC to fit into the cable so I can plug in the Glasgow for some more detailed signal tracing.
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Debugging says it’s banging against the upper cylinder limit. So basically the same problem as before, but the other direction. I wonder what it’s looking for.
Ordered some longer IDC cables so I can debug this more effectively.
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Hmm. Not working. Just keeps making that chirp sound over and over again as it accesses the drive.
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It appears that the DIR pin is operating backwards. When asserted, that should step in, towards track zero, and outwards when deasserted. So the T1200 is at track 0 and wants to step to track 1, but it's instead trying to go the other direction and staying at track 0. Repeat ad infinitum. I think I can pretty easily invert the GPIO signals.
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Manual testing shows it working now (thanks to the RP2040 designers for putting selectable inverters on both inputs and outputs before the mux), but now the laptop doesn’t want to start so I guess I’ll be testing it tomorrow.
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Same problem. But it does start to work when I increase the flash SPI clock divisor. So it could be a signal integrity problem. But there's another clue.
The below scope traces are from the "hello_uart" example. Running this several times shows that the timing is changing from run to run, and it shouldn't be. At the 115200 baud rate, only the latter part of it is decodable. If you increase the baud rate, the earlier character start to decode.
I think we have a clock stability problem. I kinda just put 33pF load caps in here. I bet that's for the HC49 cans, and I need smaller ones for the SMD crystal I'm using.
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So it’s even weirder. It will run from flash when you start in bootloader mode and do a picotool reboot, but it doesn’t run from a cold boot. Still fails when I roll back to the 2.0.0 SDK. I wonder if this is a quirk in this particular flash revision.
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It doesn't seem to want to run anything from flash, though. Hm. A problem for tomorrow.
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@MLE_online@social.afront.org I always assumed they existed for regional business conferences, but I have no idea.
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@gloriouscow@oldbytes.space Maybe not on your instance. I set mine up for a 65536 character limit. 😆
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That's still failing at a SPI clock divisor of 2. With a divisor of 8, it works. The UART trace is better, but still jittery. Let's try 18pF? That's the only other thing I have.
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18pF definitely looks better, but still failing at a clock divisor of 2. I dunno. I'll just get rid of them for now. Certainly something I'll have to fix if I want to put these into production.