• I've got extra time in a 10m EMC test chamber next week!

    02/09/2018 at 21:07 3 comments

    [EDIT: I didn't have the form configured right and folks couldn't access the questions. That has been fixed, so try the link again!]

    We're headed back for #NeuroBytes EMC testing next week (unintentional radiator) and the chamber requires a 2-hour minimum reservation. If you have a project that you are considering commercializing, I'll run a pre-test scan for you FOR FREE! Some requirements:

    • I prefer to only work with open source projects, and I want to share the results publicly. EMC testing is expensive and mysterious (at least for hobbyists), and building a public record of known-good / tested boards would be a great thing for the community.
    • Time is short. We are looking at Friday, February 16th, at 8AM in Minneapolis, MN. So you need to be ready to ship your project to me NOW.
    • I will need you to provide a self-addressed and postmarked envelope for return shipment.
    • Tests sweep from 30 MHz to 1 GHz. Standard unintentional radiator stuff. That means no radios -- ESP32, ESP8266, Bluetooth, Wifi, etc. Sorry folks.
    • Your project needs to set up and tear down quickly. As in, I plug it in (or insert batteries) and put it in the chamber, and we go. 5 minutes max.
    • This is just a pre-test -- you'll get a report but it won't give you certification.

    If you're interested, fill out this Google Form and we'll start the conversation. Again, time is of the essence here.



  • How To Fix Your Broken Onion Omega2 Board For Only $3.20

    02/03/2017 at 16:26 8 comments

    Yes, it is broken. Step One is to accept this fact:

    Above: a $5 Linux computer that uses 2mm header pins, meaning it requires a $10 - $15 dock to use.

    Step Two is to bitch about the problem on Hack Chat (you have to scroll back a few weeks to see the post). Half an hour later, be gracious when @davedarko throws together a quick PCB design and sends you the @oshpark purchase link. Get stoked and order the boards immediately (including one free!):

    Step Three: wait two weeks, find an envelope in the mail, snap apart a header, solder 64 thru-hole joints, and be excited that you saved money:

    Yes, it fits -- the board straddles half a breadboard and gives you plenty of space to pick up all 32 pins. @Onion.io: please consider changing to 0.1"/2.54mm headers like the rest of the world for your next spin, it wouldn't change the board dimensions by much and would make your product substantially more user-friendly!

    Thanks again, Dave!

  • PiZero curiosities

    01/05/2017 at 16:02 13 comments

    I picked up a Pi Zero the other day and haven't done much with it. I should have gotten the kit, since I don't have an extra uSD card lying around and I sure as heck don't have any mini-HDMI cables. Ah well.

    [photo from Adafruit]

    It's a pretty nifty board, as ten billion people (give or take) have already said at this point. As I sometimes do with circuit boards when I need to procrastinate, I grabbed my loupe and gave it a close examination. A few interesting items popped out which I've attempted to image below using an exceedingly crappy 'macro' setup (F1.8/D40, 10x loupe, remote shutter release, steady hands).

    The picture above shows a close-up of the space between the SD card slot (top) and the mini-HDMI port (not quite visible on the bottom). I was curious about the little flip-chip marked U8--it's a tiny 8 or 9 ball raw silicon chunk tied in with a few of the HDMI lines. The official RPi Zero schematic is only partial (it's missing the SD card and HDMI bits), but based on the RPi A/B schematic I believe this is a BAV99 high-speed switching diode array, as it seems to be connected to the same lines (HDMI_CEC_DAT, _SCL, and _SDA). However, I couldn't find a datasheet with a matching package, so that may be incorrect.

    The picture above shows a close-up of the mysterious(ish) Broadcom BCM2835 SOC that runs the whole board. What was most interesting to me here is the double-stack BGA arrangement; from what I can tell, the BCM2835 rides on an FR4 plate that pretty much changes the ball pitch from ~0.4mm (guess) to ~0.65mm (another guess), presumably adding an extra row or two to make up for the decreased density or perhaps dropping a bunch of connections entirely. My theory -- the high ball density of the SOC requires a higher layer count PCB for proper escape routing, so the in-between plate allows them to use the chip with a cheaper 4 layer PCB. Anyone ever seen this before that could confirm this suspicion?