Products > Test Equipment

USB testers: getting device speed etc.

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MarkMLl:
I've twice now been caught by microcontroller chips which are supposed to support "Full Speed" USB but in actual fact are only reliable at "Low Speed", at least in certain (e.g. firmware update) modes. I'd rather not "name names" since it's pretty amazing to have /any/ USB capability in a cheap chip, and a simple fix is making sure that they're connected via a USB v1 hub.

Noting the simplicity of the low/full-speed circuitry (https://hackaday.com/2023/05/09/minimal-usb-device-connects-with-just-a-couple-of-resistors/), it would obviously be easy enough to make up a tester in a project box that showed which line was being pulled up (and how strongly). However there are other situations in which D+/- are pulled or shorted, in particular by chargers (https://learn.adafruit.com/minty-boost/process and in particular the linked https://learn.adafruit.com/minty-boost/icharging), and there is a related issue with the newer connectors' ID pin (https://xdaforums.com/t/the-samsung-anyway-jig.1629359/).

Do any of the current crop of USB PD etc. testers ** report usefully on this kind of static configuration?

** https://github.com/ginbot86/DingoCharge-Shizuku lumps several designs together: "YK-Lab Shizuku USB tester (a.k.a. YK-Lab YK001, AVHzY CT-3, Power-Z KT002, ATORCH UT18)".

MarkMLl

ataradov:
It is not clear what you want to test exactly.  Are you sure you are not confusing HS and FS/LS? In most devices those resistors are not static, but configurable by the firmware on FS/LS devices. I'm not even sure there is an official way to force FS device into LS mode. There is a fallback from HS to FS, but not for FS to LS.

Also, operation at USB FS is so dead simple, that there is no reason why it would not be reliable.

thm_w:
USB PD is just using CC pins for negotiation so PD testers don't need to look at D+/D- for that.
Though they do check for other purposes, so you can easily find a tester that will display the D+/D- voltages, eg Fnirsi fnb48s, probably many others.

For the microcontroller you can just tell us the name and part number so we know what you are talking about.

MarkMLl:

--- Quote from: thm_w on March 21, 2024, 09:30:08 pm ---Though they do check for other purposes, so you can easily find a tester that will display the D+/D- voltages, eg Fnirsi fnb48s, probably many others.

--- End quote ---

But the voltage measured on the pin is distinct from the value of the pullup/down, and particularly looking at some of those Apple circuits knowing that appears to be important.

MarkMLl

ataradov:
I'm not sure what Apple circuits you are looking for, but for compliant USB devices pull-up and pull-down values on the D+/D- lines are fixed. There is no variability for any of the standard versions.

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