[HN Gopher] More than you wanted to know about how Game Boy cart...
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       More than you wanted to know about how Game Boy cartridges work
        
       Author : todsacerdoti
       Score  : 105 points
       Date   : 2025-07-22 19:17 UTC (3 hours ago)
        
 (HTM) web link (abc.decontextualize.com)
 (TXT) w3m dump (abc.decontextualize.com)
        
       | CaliforniaKarl wrote:
       | See also the Ultimate Game Boy Talk from 33c3:
       | https://www.youtube.com/watch?v=HyzD8pNlpwI
        
       | exmadscientist wrote:
       | > TI's TXB0108 for this purpose as well, which has an automatic
       | direction sensing feature that obviates the need for all of the
       | direction logic that I mentioned above.
       | 
       | Yeah, don't use these guys. They have a tendency to swap
       | translation direction in the presence of electrical noise, which
       | means your input is now an output, cross-driving something.
       | Sometimes everything survives just fine and switches back on the
       | next edge. Sometimes the magic smoke comes out. And sometimes, if
       | the stars align just wrong, you get an industrial accident.
       | 
       | This is one of those classes of parts that has hidden dangers and
       | really should not be as prominently advertised as it is. They
       | look simple, but they're for experts only. Don't use them unless
       | you really know their failure modes and don't have another
       | reasonable option.
        
       | exmadscientist wrote:
       | Also (because I feel like it/am procrastinating on other stuff),
       | some first-glance review on the design at
       | https://git.sr.ht/~aparrish/abc-pcb/tree/main/docs/abc-pcb.p... :
       | 
       | - U6 and U8 need nearby decoupling. LVC logic has horrid power
       | consumption during transitions, so best to feed it well if you
       | expect any kind of transition rate out of these gates. It doesn't
       | have to be explicitly dedicated to these parts but it needs to be
       | physically close.
       | 
       | - That goes extra for the big fat WideBus 16-wide level
       | translators. They have multiple power pins for a reason. They are
       | vicious little devices. Decouple every last power input pin with
       | its own individual capacitor.
       | 
       | - U6 outputs appear to have wrong bus directions? Probably not
       | important (also maybe not a problem at all, I usually do Altium
       | not KiCad)
       | 
       | - VBUS is not logic level, so you shouldn't use it as a logic
       | signal if you want reliability (it will work... mostly... but
       | also be weird sometimes), but you absolutely _cannot_ drive
       | multiple things with it and expect them to work (their input
       | thresholds will be slightly different and you will be sad when
       | they switch at slightly different times because it 's moving
       | slowly). Clean it up with a Schmitt trigger (1G17 etc).
       | 
       | - No ESD protection on the USB port. Do you want it to live? Try
       | something like ECMF02-4CMX8, nice and simple to implement (mildly
       | annoying to solder though).
       | 
       | - Whatever is going on with Q1 is poorly enough drawn that I
       | can't understand it at a glance. Best to just draw these parts as
       | two ordinary MOSFETS with A and B suffixes, then the circuits can
       | be legible.
       | 
       | - On IC2 (why not U2?) lines 4, 5, 6, 7 are being cross-driven.
       | Do _not_ ground both sides, you will be sad. Ground the input
       | sides and let the outputs be unconnected, because they 're
       | strongly driven by the chip. Or use resistors to pull things
       | places if you must satisfy someone somewhere who loves that kind
       | of stuff (medical! medical? medical.).
       | 
       | - U7 SENSE pin draws not-much current (~25nA) so no reason to
       | burn power in that resistor divider
       | 
       | - Consider stuffing a big fat electrolytic or two down somewhere
       | and making your PDN nicely damped.
        
       | HardwareLust wrote:
       | I find this really fascinating, thanks for sharing!
        
       | CommenterPerson wrote:
       | Congrats, Nice work!
       | 
       | .. Now go build and sell some nice IOT gadgets that do not track
       | users, and become a millionaire. Like a simple water leak
       | detector.
        
       | sigpwned wrote:
       | False, this is _exactly_ as much as I wanted to know about how
       | Game Boy cartridges work. Thank you! :)
        
         | Andrex wrote:
         | Stole my comment!
        
       | phendrenad2 wrote:
       | I was sad to see that one of my old favorite GB dev resources is
       | gone:
       | https://web.archive.org/web/20150410063839/http://www.devrs....
       | 
       | Most of the links were already long-long-dead, but there were
       | some cool inspirational projects on there.
        
       | asdff wrote:
       | My Pokemon blue version went through the washer and dryer
       | probably 20 years ago and it still works to this day. Talk about
       | some hardware. I wonder if an SD card would take that sort of
       | abuse.
        
       | toast0 wrote:
       | > You don't need to circumvent copy protection or region lockout
       | hardware to write custom software for the Game Boy, since the
       | Game Boy has none.
       | 
       | While there's no region lockout, don't you need to pass the logo
       | check?
        
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       (page generated 2025-07-22 23:00 UTC)