Re: Raspberry Pi 3B USB Printing Issue
- Reply: Archimedes Gaviola : "Re: Raspberry Pi 3B USB Printing Issue"
- In reply to: Hans Petter Selasky : "Re: Raspberry Pi 3B USB Printing Issue"
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Date: Sun, 13 Mar 2022 06:27:09 UTC
On Sun, Mar 13, 2022 at 12:38 AM Hans Petter Selasky <hps@selasky.org> wrote: > 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! > Thank you so much Hans for answering my questions, really appreciate it! I have a much better understanding now. I came from testing with 13.0-RELEASE having the same RPi 3B hardware and setup and it's very stable. I haven't encountered any IOERROR and incomplete printed outputs that were encountered with 14.0-CURRENT (February 24, 2022). By the way, I found in the repository here https://download.freebsd.org/snapshots/arm64/aarch64/ISO-IMAGES/14.0/ that there were two latest snapshots released dated March 3 and March 10, respectively. I need to take printing tests first, especially the latest to check if it also manifests before I go back to the Feb. 24 snapshot and do a thorough test with debugging. I'll provide updates for any observations. Thanks, Archimedes