Post B7gou1boF3NabjAy2q by whitequark@social.treehouse.systems
(DIR) More posts by whitequark@social.treehouse.systems
(DIR) Post #B7fEMJRLeFUYYYwqq8 by mntmn@mastodon.social
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any experience with how usb-c to displayport cables with chrontel chip are "activated"? my guess is i need VCONN, otherwise it won't respond to VDMs? or do i need to send VDMs to SOP' / SOP''?
(DIR) Post #B7fMQKAZg3KHbuWhDE by whitequark@social.treehouse.systems
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@mntmn former is almost certainly true at least
(DIR) Post #B7fMQKOOqeNwImzjlI by mntmn@mastodon.social
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@whitequark OK. gonna bodge it and see (past me was like, who needs vconn anyway?!)
(DIR) Post #B7fMnIR8HogetdE1iq by whitequark@social.treehouse.systems
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@mntmn isn't it required by the spec
(DIR) Post #B7fMnIhnHs0xjJ1Kgy by mntmn@mastodon.social
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@whitequark afaik (i might certainly be wrong) only for USB-C PD sources >=3A and for USB4
(DIR) Post #B7fMq6HvuUiS5UG8XY by mntmn@mastodon.social
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@whitequark and, i guess, for alt-mode stuff...
(DIR) Post #B7fTG4yxzHzvI89uE4 by mntmn@mastodon.social
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@whitequark ah yeah the billboard's USB descriptor says it wants 1W VCONN power (lowest possible)
(DIR) Post #B7fg05peMLCMhJVaTI by whitequark@social.treehouse.systems
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@mntmn oh i think i see how this happened now
(DIR) Post #B7fg060zgAGxGUoe9Y by mntmn@mastodon.social
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@whitequark btw i can't snoop on USB-CC with glasgow by any chance right?
(DIR) Post #B7gn5dfQsk0vv9HTI8 by whitequark@social.treehouse.systems
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@mntmn not as-is with revC (it is too low voltage), revD does have Vio low enough for it. you could fudge something with FUSB302 (easy) or add a comparator and use an LA (less easy)
(DIR) Post #B7gn5dqQDsnwTEQFQ8 by mntmn@mastodon.social
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@whitequark i have plenty of fusb302 (because i use that to talk PD in the pocket reform and in the next) buuut i don't know if it works in a 3-way configuration (as a sniffer listening on CC lines between 2 other devices so i can record that). but maybe it does? and with glasgow i could script fusb302 over i2c?
(DIR) Post #B7gn8YAVmZpLjfCpiy by mntmn@mastodon.social
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@whitequark and/or low tech option might be to sniff with oscilloscope and transfer waveform to computer, decode
(DIR) Post #B7gnZDX0cR0TY7Rdmi by 23n27@dgc.social
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@mntmn Sorry to hijack this thread. I love the FUS302 but I have had problems with when trying to talk to PD3.0 peers in the past. Have you seen similar problems or am I just holding it wrong after all?(Screenshot from the commit message of my patch for working around this on Linux by disabling PD3.0 support)
(DIR) Post #B7gou1JjKGuxheiWrg by whitequark@social.treehouse.systems
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@mntmn looking into it
(DIR) Post #B7gou1boF3NabjAy2q by whitequark@social.treehouse.systems
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@mntmn i have not tested this but going by the datasheet, if you set:AUTO_CRC=0TXCC1=0TXCC2=0AUTO_PRE=0TOGGLE=0then it shoooould be passive?
(DIR) Post #B7gou1mnaCAb9oJkAq by mntmn@mastodon.social
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@whitequark aw many thanks for researching that, will try it out!
(DIR) Post #B7gou2zx4mHkutTlJY by whitequark@social.treehouse.systems
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@mntmn and yeah scripting fusb302 with glasgow should be pretty easy, see https://glasgow-embedded.org/latest/applets/interface/i2c_controller.html#module-glasgow.applet.interface.i2c_controller
(DIR) Post #B7gou4ORtBTVF9wq8W by whitequark@social.treehouse.systems
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@mntmn if you doglasgow script myscript.py i2c-controller -V 3.3 --scl A0 --sda A1then you can write code as described in the docs in myscript.py, with i2c_iface being your I2C controller interface
(DIR) Post #B7hFyzR4RkoM4skFSC by mntmn@mastodon.social
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@rwhitby @whitequark wow ok, kind of exactly what i need
(DIR) Post #B7hifc5JwBt8pDgU3k by mntmn@mastodon.social
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@23n27 interesting. so far i've been sending pd specrev 2
(DIR) Post #B7hihfjnKMj0jWb6HI by mntmn@mastodon.social
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@whitequark well it's going slowly
(DIR) Post #B7hizJnrcM11uwunVQ by mntmn@mastodon.social
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@whitequark phone and the displayport cable discussing something
(DIR) Post #B7hk0Fn47fsRiQYFzk by 23n27@dgc.social
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@mntmn I checked this with an USB-PD analyzer but didn't really chart the exact shape of the problem because throwing in this workaround (simply nuking PD3 support in the kernel) was good enough back then.At some point I should look into this and maybe add a quirk to the upstream driver.
(DIR) Post #B7hm71FklorWZ3K8kC by whitequark@social.treehouse.systems
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@mntmn went with the scope route?
(DIR) Post #B7hm71RS4KDh9KnTyi by mntmn@mastodon.social
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@whitequark yeah that's step 1, to see if there is a signal at all and that it looks ok (that my very improvised sniffer pcb works). and thennn someone told me that my dusty DS16 pro can do very low logic levels. so i tried it right now:
(DIR) Post #B7ifjhIEPTl5QqwGzA by magnetic_tape@infosec.exchange
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@mntmn(Sorry for hijacking this thread but do you have issues with your DS16pro and Pulseview/Sigrok? I heard about some drama years ago and I remember not being able to use the DS16 with vanilla Pulseview/Sigrok and had to use a custom build from DS. I wonder whether this has been fixed or not nowadays)
(DIR) Post #B7ipHSjPxGSzhgpXZQ by mntmn@mastodon.social
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@magnetic_tape it seems to be fixed, it works with sigrok/pulseview from debian. it needs 2 firmware files that it uploads automatically, i got them from the sigrok wiki
(DIR) Post #B7isYd5wycoUdAFOSG by magnetic_tape@infosec.exchange
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@mntmnThanks for the info!