Date: Sat, 12 Mar 2022 17:38:34 +0100 From: Hans Petter Selasky <hps@selasky.org> To: Archimedes Gaviola <archimedes.gaviola@gmail.com> Cc: freebsd-arm@freebsd.org Subject: Re: Raspberry Pi 3B USB Printing Issue Message-ID: <dabb798c-435c-6dd3-ac9b-8db3fb02a43c@selasky.org> In-Reply-To: <CAJFbk7GwjFA-=GrJG3KTCnqVfEPhRSY1g8xyws_nE8pAohErEg@mail.gmail.com> References: <CAJFbk7EzSfPNbaGxiweKrivwNrKXCPVzA1b7_=0_bTvbs8oBow@mail.gmail.com> <7c67118e-f6ec-c87d-9a81-3ee6a5952f49@selasky.org> <CAJFbk7GYbLAFTJY077Nzh3CTBJM6bk8swr4AkgGMaukCxrfcHQ@mail.gmail.com> <60f98b10-dcdc-cdf4-3d7a-fe9fd4dff223@selasky.org> <CAJFbk7EAjrQG5Kj_upVKW72opOS%2B8d63VrMnQdLxcJjUcfsd=g@mail.gmail.com> <8226461b-5740-9c19-0575-2740bd952e16@selasky.org> <CAJFbk7GwjFA-=GrJG3KTCnqVfEPhRSY1g8xyws_nE8pAohErEg@mail.gmail.com>
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On 3/12/22 16:31, Archimedes Gaviola wrote: >> >> IOERROR usually means an electrical error. The RPI3B will use a >> transaction translator for the FULL speed traffic, which is driven by >> software. > Hi Archimedes, > Hi Hans, > > I'm curious about the transaction translator you've mentioned, any idea why > there's a need for translation and what is being translated? When the High Speed USB HUB was invented, there was a need to support FULL and LOW speed USB transactions. Because FULL and LOW speed transactions are slow and take up much bandwidth, a transactions translator was invented which translates between High Speed USB and FULL/LOW speed USB. That means the RPi 3B consists of a single USB HIGH speed port, followed by a USB HUB. These transactions are not visible in usbdump . >Does this only > happen when RPi 3B (acting as host controller) is transmitting data to the > Epson printer? Are translation events visible in the usbdump? In this case > there's a way to possibly track what's going on and how to identify any > info that is being translated? By turning on the HC debugging, you can possibly track via debug messages what is going on. Maybe it is a timing issue, that the SW is too slow serving the micro transactions. Any idea also if translation is being > performed in RPi 4B? The later RPi's do the transaction translator bits in HW or via the XHCI block. As I have conducted several printing cases with my > Epson printer without any issues with either of the 4 ports. > > Sorry for these questions as I am catching-up to the USB technology > internal workings under the hood. You are welcome! --HPS
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