Monday, April 3, 2017

Badly Behaving USB 3.0 Hub?

I just ran into an interesting issue with my desktop computer:

I have a 7-port USB 3.0 hub attached. It has been part of my system for a short while and have had no issues until recently.

I usually just plug in USB 3.0 thumb drives into the hub, so I haven't had a need to use the +5V/2A adaptor that comes with the hub. But recently, I have been plugging in a portable USB-powered hard disk into it and I decided I had better use the adaptor to make sure all current requirements are met.

Well, I started having some weird keyboard issues this morning, and I decided to shutdown (turn off) my system for a short bit and then reboot. But when the system shutdown, the drive LED was still lit!

I didn't want to do a hard shutdown, for fear that something being written to the hard disk would get corrupted (although, I didn't hear any typical hard disk noises).

Then I happened to look at the USB hub with the power plug going into it. I removed the plug and ... the drive LED went out! It turns out that the USB Hub was feeding the external +5V from the adaptor back into the motherboard! YIKES!

So - I opened the hub and identified the trace that was bringing +5V from motherboard via the main USB plug of the hub and ... just cut it.

Now, I will _always_ have to have the +5V adaptor plugged into the hub - it will no longer power by itself when plugged into the motherboard USB. But that's okay, because I planned to use the +5V adaptor anyway, and now the USB hub power does not feed back into the system. Annnnd it shuts down properly now.

But ... I wonder who is at fault? Is the motherboard supposed to block +5V coming back in from a hub? Or is the hub supposed to keep it's +5V from feeding back into the motherboard?

I could install a 1N4007 diode as a blocker between the +5V from the hub and the +5V from the desktop, so it won't feed back into the motherboard, but ... I worry about the 0.7V drop across the diode. Would the voltage inside the hub be only +4.3V when connected with the AC adaptor? Maybe. 

I need to do a few experiments to confirm that but not today. I have work to do and everything is working well enough. For now.

Monday, March 20, 2017

Fisher RVR-4910 Remote with Shuttle

My favorite remote for development / debugging. An old Fisher RVR-4910 with a Shuttle Knob. For some reason I felt compelled to document it.

Monday, March 7, 2016

Still Building Parols

Aside from the Arduino post I just published - has it really been almost 2 years since I've written anything for the blog? Oy, vey. Too busy for my own good, I guess.

Still building Filipino Christmas parols. Lots and lots of them. Playing with WS2812B IA RGB LEDs, too, but I'm having a hard time figuring out the right way to mount them in the parols so that they look best and are somewhat equivalent in brightness to standard 1 color LEDs.

Oh well.

It may be another 2 years before I publish anything else. Don't be surprised.

Dipping A Toe Into The Arduino Pond

Arduino MEGA with Ethernet Shield

Training Shield
I bought an Arduino board, training shield, and ethernet shield this weekend at the SM Megamall. Never too old to learn new things. So far, not really impressed - I'm still convinced that the right MicroChip PIC, chosen for the job at hand, is far superior (and cost effective). I'm still wading through the Arduino, however, so it still has the opportunity to win me over.

BTW: what is it with 'sketch' and 'sketches'? WTH? Wasn't 'programs' and/or 'source code' and/or 'projects' good enough for Italians? Too cute for it's own good.

Also BTW: not digging the 'C'-like language. Give me assembly any day. You can write faster, leaner, more efficient code in assembly. At least all of the code is open source, so you can dig into it and know what all it is doing.

Also also BTW: I _am_ digging the shield concept. Nice for initial prototyping. I will have to come up with my own 'proto-board' shield, tho. They didn't have one at the store I visited at SM Megamall.

*UPDATE - 2016.0311*
I made my own "prototyping shield". Cool. Now to figure out something nice to prototype on it.

Left: Arduino Mega           Right: Prototyping Shield

Prototyping Shield installed on Arduino Mega