12 responses to “EEVblog #12 Part 2 of 2 – Shanghai Special – Dodgy USB hubs”

• Jonno June 8th, 2009 at 00:05

  Funny coincidence. I’ve had a cheapy usb hub and 2 of the 4 ports slowly died. Still powered up but all errors in dmesg. Took it apart and could not believe my eyes. Utter-crap. Didn’t even bother going any further and chucked it.

  Reply

• Daniel June 8th, 2009 at 04:08

  I dont think I have ever encountered a good usb hub!

  I enjoyed both videos, the first was very interesting.

  If you need an idea for a future episode: why don’t you delve more into why you do not like ceramic resonators?

  I use:
  http://www.abracon.com/Resonators/AWCR_MD.pdf

  Quite often, and actually prefer it to crystal resonators. It is faster, pre-balanced with capacitors, better package, and more apt to handle shock vibration than any crystal. I know there is a little more clocking error but it is minimal, on anything you would probably use it for anyways? I think its more per application. If you need high precision/speed communication, then I would use a crystal, and I have yet to use an application where it was unacceptable.

  Although I am only just starting out in my Design career.

  An example of what was acceptable, a project I recently did to graduate, I used a PIC18F4550 if you are familiar, and used a 20Mhz ceramic resonator because it was available. When you input 20Mhz to that uC I opted to use the chips fastest clockspeed. So I used internal hardware and PLL of the chip to effectively transform my clock:

  Clock >> 20M >> 4M >>PLL=96M >> 48M >> CPU.

  You would think this just propagated and expanded the initial error of the resonator and would have made my serial communication terrible, but I had no problems at all, even at the moderate speed I was communicating with my GPS module (38400 Baud)

  Reply

  • admin June 9th, 2009 at 08:47

    Ceramic resonators are fine for general CPU usage and serial UART communications, but are not the best for USB communication for example.
    With Serial UART communications can even get away with using the internal trimmed RC oscillator in todays micro’s, no need for any external parts at all.
    You can actually get special ceramic resonators designed for high speed USB application (e.g. Murata Ceraloc), but generic ones are a dodgy choice.

    Reply

• Ford June 9th, 2009 at 05:49

  Thanks for making such an easy to follow blog with practical information!

  Do you have any suggestions for decent, low cost soldering equipment? I have a cheap Radio Shack iron that is OK for basic through hole stuff but no good for anything else. Trying to solder a LCC-8 package was a nightmare.

  Reply

  • admin June 9th, 2009 at 08:49

    Without hesitation – the Hakko 936.

    Reply

• Daniel June 9th, 2009 at 09:11

  @Ford,

  Anything from Hakko and Weller are good choices.
  I am personally a Weller fan and have a WESD51. Thinnest Soldering pen I have come across.

  http://www.amazon.com/Weller-WESD51-Digital-Soldering-Station/dp/B000ARU9PO

  I have read that SparkFun uses Aoyue brand which is also available on amazon. And from what i’ve seen for the price of a Goodiron and station, you can get an iron and a hot air rework setup.

  http://www.amazon.com/Aoyue-968-Digital-Rework-Station/dp/B000HDG0AO

  Have any of you seen the Hakko FM-2026 Nitrogen Soldering System?

  As far as I can tell, it strips Nitrogen out of the atmosphere and burns it, being hotter and ideal for Lead Free applications. Way too hardcore though.

  Reply

• Aaron June 11th, 2009 at 15:44

  Hi David, I recently stumbled across your website and have spent the past day or two watching all the videos. They’re great! Thanks for all the information. Reading over some of the comments others have made, it seems there are a lot of people interested in equipment reviews and recommendations (I know I am!). Perhaps you could do a segment on test equipment everyone who is serious about electronics should have, and recommend some entry level hardware. Things like oscilloscopes, power supplies, function generators and whatever else you think everyone should have in their lab. Just a suggestion of course.

  Thanks again for great videos, I’m already looking forward to the next one!

  Reply

• Dan June 17th, 2009 at 08:32

  I find myself frequently visiting this blog, hoping for an update. Fantastic to follow, always something interesting, and there’s very few good EE blogs out there, if any.

  Reply

• Alex June 18th, 2009 at 13:37

  Speaking of oscillators, I don’t understand why Microchip have put RC oscillators on their dsPIC family and the “precision” oscillators on the lower-performance PIC18 family. PIC24 have both types. I’ve played with a dsPIC, and the frequency was way off… At the same time, the PIC18 chips were spot on. Is it the cost? I would assume more precision is needed on DSP applications, to get sample rates right… Or is nobody using the internal oscillator in the real world? (I’m a student)

  Reply

• Jim H. July 22nd, 2009 at 03:11

  Great presentations.

  I noticed on the cheap USB hub that all of the USB connectors have pin 1 (Vcc) tied in parallel. Each PC is supposed to supply some power to this pin. Connecting these all together seems like an extremely poor practice.

  cheers

  Reply

• John W. August 18th, 2009 at 10:14

  I love the differences shown between the cheapo soldered-in-the-back-alley glop-top USB hub and the higher-quality unit, which lacks the blob of epoxy around the IC’s and actually has decoupling/filtering caps (at least that’s what they LOOK like they are. They’re pretty large.)

  Another fantastic video. Keep ‘em coming

  Reply

• Bob August 24th, 2009 at 23:18

  I once bought a usb A->B cable for $1.80 at dealextreme, hooked up my homemade pickit2 with it, and found that it didn’t work that well.

  So I started measuring on the thing, thinking that I made a mistake, and found that the 3.3 volt dspic I had on there only got 2.5 volts on its power supply.

  Well that was a bit strange, so I measured the usb voltage and saw that it was only about 4 volts.
  I hooked up another usb cable and with that one the usb voltage was fine.

  Well maybe I had a broken usb cable, so I measured the resistance of the wires and found that all four of them had a resistance of 3 ohms, which is ridiculous for a 1.5 meter cable.

  I didn’t cut the cable to see what’s inside, but I have a suspicion the manufacturer used iron instead of copper for the wires.

  Reply