USB testers: getting device speed etc. - Page 1
Forum section: electronics / testgear

author: MarkMLl
author_rank: Frequent Contributor
timestamp: March 21, 2024, 06:00:00 pm
content: 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/processand in particular the linkedhttps://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-Shizukulumps several designs together: "YK-Lab Shizuku USB tester (a.k.a. YK-Lab YK001, AVHzY CT-3, Power-Z KT002, ATORCH UT18)".MarkMLl

author: ataradov
author_rank: Super Contributor
timestamp: March 21, 2024, 08:25:12 pm
content: 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.

author: thm_w
author_rank: Super Contributor
timestamp: March 21, 2024, 09:30:08 pm
content: 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.

author: MarkMLl
author_rank: Frequent Contributor
timestamp: March 22, 2024, 07:00:39 am
content: Quote from: thm_w on March 21, 2024, 09:30:08 pmBut 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

author: ataradov
author_rank: Super Contributor
timestamp: March 22, 2024, 02:46:18 pm
content: 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.

author: MarkMLl
author_rank: Frequent Contributor
timestamp: March 23, 2024, 09:10:42 am
content: Quote from: ataradov on March 22, 2024, 02:46:18 pmThe ones I cited in my OP> in particular the linkedhttps://learn.adafruit.com/minty-boost/icharging)MarkMLl

author: JohnC
author_rank: Contributor
timestamp: March 23, 2024, 01:29:11 pm
content: You are confusing Charging current with DATA SPEED.You first ask about reliable "Full Speed USB" which relates to data transfer.Yet then you start talking about Apple and Mintyboost which relates to Charging Current negotiation. The Hackaday link doesn't refer to anything that you are talking about.So, how about you start again, and clarify what exactly you are trying to determine?

author: ataradov
author_rank: Super Contributor
timestamp: March 23, 2024, 03:00:49 pm
content: Quote from: MarkMLl on March 23, 2024, 09:10:42 amThis article does not tell what is different in Apple devices at all. And then just describes a primitive boost converter.The only thing I could find in the FAQ is that iPad will not try to conserve power if it thinks it is being charged. This is not a USB issue, this is iPadt issue, and I don't know how applicable is the article from 2013 to today.