Post AkbsfKebhbo13PZ2hs by violator@mathstodon.xyz
(DIR) More posts by violator@mathstodon.xyz
(DIR) Post #Akbrg6xpzDfgvnMnfE by foone@digipres.club
2024-08-04T02:43:34Z
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So I have a PCB which has a QFP-64 mcu on it that I can't reprogram. So I'm going to remove it, and drive the LCD display pins directly.Does anyone know an easy way to do this? Either a flat flex cable with the right pitch so I can solder one end to the qfp-64 footprint, or some kind of reverse Qfp64 breakout?
(DIR) Post #AkbsfKebhbo13PZ2hs by violator@mathstodon.xyz
2024-08-04T02:48:32Z
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@foone my go-to would be to solder magnet wire to each pad of interest, especially if the LCD interface doesn't consume the full 64 pin pinout
(DIR) Post #AkbskdD08yD434B8r2 by foone@digipres.club
2024-08-04T02:49:43Z
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@violator yeah that's my backup idea. I'd just love to avoid having to do something like 30 wires manually
(DIR) Post #Akbsr0pHFQWr2A7mr2 by violator@mathstodon.xyz
2024-08-04T02:57:31Z
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@foone have you ever used a z-axis elastomer? They're very handy, particularly when constructing custom test sockets. It would not be a permanent solution (I assume), but would allow for testing as to whether the pitch of your ribbon cable is correct
(DIR) Post #AkbtR2EfU6eHpYB5wu by foone@digipres.club
2024-08-04T03:04:07Z
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@violator that's actually what I'm trying to do here! I'm connecting to the microcontroller footprint because it's easier than attaching to the elastomeric connector
(DIR) Post #Akbtb30zRRh98xYRLU by violator@mathstodon.xyz
2024-08-04T03:05:44Z
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@foone ah, well, the larger footprint at least allows for a wider pitch ribbon maybe? what are you trying to drive with, that interface might inform the approach, if you don't mind me asking
(DIR) Post #Akc0OcRd6S9UwQ2H5s by abrasive@digipres.club
2024-08-04T04:21:21Z
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@foone could you use a zebra strip and mush an 0.5mm pitch FFC down on it? though that's probably harder than directly soldering an FFC to the QFP pads
(DIR) Post #AkcQ7wmSq3PPtiUXia by byteborg@chaos.social
2024-08-04T09:10:03Z
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@fooneWould it be viable for you to design a small breakout board in KiCad? I imagine a qfp64 footprint with shortened traces that end in half vias, such as the esp modules do. So you'd get a drop in to be soldered with a heat gun. You could even produce it as flex and have the cable directly integrated.
(DIR) Post #AkcTrbSuij0uyMoEpU by dtelder@mastodon.nu
2024-08-04T09:52:08Z
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@foone Put a wide ffc between pcb and elastomer and lead to an external mcu?But I have no idea if possible to drive the lcd using io-pins directly. Perhaps there are general lcd-driver-ics?
(DIR) Post #AkdTReYkmuyMCL7vGa by foone@digipres.club
2024-08-04T21:22:09Z
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okay these are approximately .4mm pitch. that is not going to be fun to solder. so I'm not gonna. I'm going to have to take a different approach
(DIR) Post #AkdU19VfhvIqK9c2XQ by myersjustinc@mastodon.sdf.org
2024-08-04T21:28:36Z
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@foone Chip Quik, a _lot_ of flux and a (hopefully) good layer of existing soldermask?
(DIR) Post #AkdUGOjrMx9dtoWDLs by foone@digipres.club
2024-08-04T21:30:51Z
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This is the PCB I want to modify.Soldering to the chip's pads is going to be too much of a pain, so either I'm gonna try to solder onto those small test pads on the bottom, or I just make my own PCB with pads in the same places.
(DIR) Post #AkdURqDpWjP4K4zf04 by futurebird@sauropods.win
2024-08-04T21:34:13Z
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@foone What kind of iron do you use? I like the TS101 it heats up very fast, and with the extra pointy tip you can set it to 350C and it's great for this kind of thing. The same company makes a tiny little hotplate for SMD work that's pretty great.
(DIR) Post #AkdVnstoM0fux0hklU by blinken@hachyderm.io
2024-08-04T21:48:01Z
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@foone any way you slice it will be a pita, but in the past I've had success with "fine wire and solder paste + hot air"Tape the fine wire to the board with kapton tape until it lines up perfectly with the pin you need in steady state (this may take 30 minutes of retrying), dab on the finest amount of solder paste (I use a fine-point plastic spudger), then when you're sure hot air + very fine tweezers to clear the inevitable bridges.I've never had success with a soldering iron directly
(DIR) Post #AkdZqHpL2kmSev0thg by abrasive@digipres.club
2024-08-04T22:33:53Z
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@foone I don't suppose that's a 1mm pitch on that thar LCD connector? if the LCD frame is friendly you could stick a 1mm FFC under there and poke the other end into a breakout eg. https://www.aliexpress.com/item/1005005319261974.html
(DIR) Post #AkdbQ2blCkG9pyH8W8 by foone@digipres.club
2024-08-04T22:51:37Z
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@abrasive good idea. I'll look into that. thanks!
(DIR) Post #AkddgkvwN439qsoRAO by Specialist_Being_677@hachyderm.io
2024-08-04T23:17:00Z
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@foone ooh that's interesting. I usually only see that company on Bluetooth ICs (Bluetooth audio mostly) but I don't see an inverted F antenna on the PCB...
(DIR) Post #Akdg1vH3Jua1ubuNaS by foone@digipres.club
2024-08-04T23:43:15Z
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@Specialist_Being_677 yeah, no bluetooth in this one. it's just a wrist bloodpressure monitor
(DIR) Post #AkdgRT3KrunDulfn7Y by Specialist_Being_677@hachyderm.io
2024-08-04T23:47:46Z
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@foone oooh I bet there's a Bluetooth version of it though.
(DIR) Post #AkdhOrt4B7x81SC5wW by foone@digipres.club
2024-08-04T23:58:25Z
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@Specialist_Being_677 oh I'm sure.
(DIR) Post #AkeBqmRF1mLprAP9pA by simon_bitdiddle@mastodon.sandwich.net
2024-08-05T05:39:48Z
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@foone Couldn't you put a socket over the chip?
(DIR) Post #AkliZw8cMuehbtzOrY by todbot@mastodon.social
2024-08-08T20:36:54Z
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@foone If you don’t care about the chip, use a sharp hobby knife or scalpel to cut the chip legs, then desolder them. Otherwise, I’ve used a hotplate as a pre-heater and a heat gun and flux to lift up the chip
(DIR) Post #AkllqbyUt73brPtkga by doctormo@floss.social
2024-08-08T21:26:52Z
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@futurebird @foone Out of context I thought at first iron was some special mix of iron, like what do you use in your forge. On a second reading an hour later, I thought oh, it must be for clothes, like a model of iron for cloths.As a double fool, I click to read the thread and it's electronics. This makes the most sense 😅🤭