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   ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Monday, 02-Jun-2025 00:04:56 JST ✧✦Catherine✦✧

   • Inter-Integrated Catgirl

   samtec has an obscene JTAG cable assembly (via @G_glop)

   i think the moment you start rating your JTAG connector at "7 dB insertion loss", something has went very, very... strange

   • Embed this notice
     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Monday, 02-Jun-2025 00:09:06 JST ✧✦Catherine✦✧

     in reply to

     this looks like a shitpost i would made about JTAG except it's inexplicably real https://suddendocs.samtec.com/catalog_english/hhsc.pdf

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     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Monday, 02-Jun-2025 00:12:45 JST ✧✦Catherine✦✧

     in reply to

     people say things like "breadboards are 10 MHz max" (basically true) from which they derive conclusions like "pin headers, which have the same pitch as a breadboard, are 10 MHz max" which are entirely false. although you do need to treat it like a transmission line above ~20 MHz or nothing will work

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     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Monday, 02-Jun-2025 00:16:23 JST ✧✦Catherine✦✧

     in reply to

     • Henning Paul DC4HP

     @hennichodernich this is exactly what glasgow does! though 30 ohms still results in a lot of crosstalk

   • Embed this notice
     Henning Paul DC4HP (hennichodernich@radiosocial.de)'s status on Monday, 02-Jun-2025 00:16:24 JST Henning Paul DC4HP

     in reply to

     @whitequark yes. Yes, yes, yes.
     Use IDC cables with every second wire grounded and 22 to 33 ohms series resistors on the TX side.

   • Embed this notice
     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Monday, 02-Jun-2025 00:17:21 JST ✧✦Catherine✦✧

     in reply to

     • Henning Paul DC4HP

     @hennichodernich edit: i now realize i've never properly measured crosstalk where every data line has been a part of a twisted pair, it might be okay already. 100 ohm more inline definitely helps

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     slaeshjag (slaeshjag@bitbang.social)'s status on Monday, 02-Jun-2025 00:31:15 JST slaeshjag

     in reply to

     @whitequark My favourite example of a connector that does. not. look high speed, is probably the subconn DBH13M. Good for gigabit ethernet (and separate power!), just remember to lube it up well first

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     dram🎀 (dramforever@mastodon.social)'s status on Monday, 02-Jun-2025 01:28:27 JST dram🎀

     in reply to

     @whitequark pmods can run differential pairs. i've always wanted to try to get pmod hdmi working. granted, hdmi can tolerate a bit more BER

     there's no standard on how the pins pair up on a pmod so that's always fun.

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     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Monday, 02-Jun-2025 04:34:54 JST ✧✦Catherine✦✧

     in reply to

     • Manawyrm | Sarah
     • Henning Paul DC4HP

     @hennichodernich @manawyrm yup! this is actually somewhat of a happy accident: at the time I came up with the pinout I only had a cursory idea about signal integrity, but I figured that the Cortex JTAG connector can't be that bad, so I copied it almost verbatim. It worked out flawlessly

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     Henning Paul DC4HP (hennichodernich@radiosocial.de)'s status on Monday, 02-Jun-2025 04:34:56 JST Henning Paul DC4HP

     in reply to

     • Manawyrm | Sarah

     @manawyrm @whitequark Indeed, and fortunately the Glasgow supports this by putting GND on even pins 4-18.

   • Embed this notice
     Manawyrm | Sarah (manawyrm@chaos.social)'s status on Monday, 02-Jun-2025 04:34:57 JST Manawyrm | Sarah

     in reply to

     • Henning Paul DC4HP

     @hennichodernich @whitequark that's basically parallel ATA :D

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     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Monday, 02-Jun-2025 06:16:31 JST ✧✦Catherine✦✧

     in reply to

     • Chartreuse
     • Inter-Integrated Catgirl

     @ChartreuseK @G_glop exactly my question!!

   • Embed this notice
     Chartreuse (chartreusek@social.restless.systems)'s status on Monday, 02-Jun-2025 06:16:32 JST Chartreuse

     in reply to

     • Inter-Integrated Catgirl

     @whitequark @G_glop who's doing JTAG at 2.7GHz?

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     🇺🇦 haxadecimal (brouhaha@mastodon.social)'s status on Monday, 02-Jun-2025 06:42:53 JST 🇺🇦 haxadecimal

     in reply to

     • Inter-Integrated Catgirl

     @whitequark @G_glop
     I love the 38 AWG coax ribbon. Awesome stuff!
     OTOH, I don't love anything that needs that for JTAG.

   • Embed this notice
     poleguy (poleguy@mastodon.social)'s status on Monday, 02-Jun-2025 06:50:25 JST poleguy

     in reply to

     • Inter-Integrated Catgirl

     @whitequark @G_glop How much does this cost... hmmm... (What's the part number?)

     Can confirm pin headers don't fail at 10 MHz. I currently have 800Mbps data running on a 0.100" pitch header on my bench:

     https://mastodon.social/@poleguy/114512955425762180

     I did solder in a 0201 differential termination and added 4 dB attenuation to get the voltage down within spec, because the input signals are HSTL and the receiver is set to LVDS.

     If cheap enough these cables could make cheap/fast board-to-board serial links possible.

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     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Monday, 02-Jun-2025 07:07:28 JST ✧✦Catherine✦✧

     in reply to

     • poleguy

     @poleguy
     HHSC–105–10.00–SE–TE
     HHSC–108–06.00–SU–TU

   • Embed this notice
     poleguy (poleguy@mastodon.social)'s status on Monday, 02-Jun-2025 07:11:30 JST poleguy

     in reply to

     @whitequark Our samtec rep seems to get a bonus based on how many free samples he hands out, so cost is not really a concern if I just need a couple.

     But anything that requires a quote to get a price is hopefully never something that I specify on a board that I design. Oh well, no surprise really.

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     Tube❄️Time (tubetime@mastodon.social)'s status on Monday, 02-Jun-2025 11:23:43 JST Tube❄️Time

     in reply to

     @whitequark sudden strangeness

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     🇺🇦 haxadecimal (brouhaha@mastodon.social)'s status on Tuesday, 03-Jun-2025 06:46:53 JST 🇺🇦 haxadecimal

     in reply to

     • Inter-Integrated Catgirl

     @whitequark @G_glop
     Full catalog page is
     https://suddendocs.samtec.com/catalog_english/hhsc.pdf
     (You already had this, but I had to dig a bit to find it.)
     There seems to be nothing JTAG specific about it; I wonder why they reference JTAG at all.
     They say it's ribbon coax, but I don't understand how they wire it, as they appear to have one coax per connector pin position. I assume that goes to the center pin, but then what is tied to the shield? They don't designate any connector pins as being ground or shield.