Power Playground Project


Power Playground

Here's a few pictures of my latest project: "Power Playground."  It's a PMOS/NMOS H-Bridge with FETs that can handle 3 amps or so, plus a SPI current sensor, some switches & a rotary encoder (not stuffed yet), and a 7-segment display, all controlled by a Teensy-3.1 running FreeRTOS.

DorkbotPDX Code of Conduct

DorkbotPDX Code of Conduct


DorkbotPDX is committed to providing a socially safe and friendly environment for people doing strange things with electricity.  We welcome all, regardless of techical experience, gender, sexual orientation/identity, age, ability, ethnicity, religion, or physical/biological cybernetics.

DorkbotPDX expects attendees to be:

  • respectful - Don't seek to irritate, annoy, or otherwise disrupt others.
  • cautiously helpful - Share what you know, but don't assume you know more than someone else.
  • engaged - If you're curious and wondering, just ask.  If you're asked, try to answer or brainstorm.

Because we wish to foster an open, diverse, and engaged community, DorkbotPDX does not tolerate discrimination or harassment.  We are particularly sensitive to discrimination against and harassment of socially marginalized groups.

Any person in violation of these guidelines may be warned or asked to leave.  If you are aware of any behavior in violation of these guidelines, please notify a DorkbotPDX organizer.

Art and tech events this week!

We are extremely lucky this week to have THREE art/tech events happening here in Portland featuring artwork from some of our favorite creative coders. Have fun and support your art/tech community by coming out for these events! The first two are part of First Thursday and you can easily walk between them.

Dungeon Hacker at DIODE Gallery Thursday Feb 5 6PM-9PM 514 NW Couch Featuring Dan Cohen, Ryan Johnson, Andy Lunday, and Gabe Shaughnessy http://www.augmentedart.com/hack-the-dungeon/

Electric Fields by Jeremy Rotsztain at UPFOR Gallery Thursday Feb 5 6PM-8PM - 929 NW Flanders http://www.upforgallery.com/future/


ByteMe 4.0 at AFRU Gallery Friday Feb 6 6PM-11PM - 534 SE Oak St. Featuring Church of Robotron, Libby White, John Brown, Ben Purdy, and more! http://www.afrugallery.com/event/byte-me-4-0/

A few of us worked on the Church of Robotron install for ByteMe, so here's a far too large flier for it!

VS1053 Troubleshooting

Last night, I looked into why Adafruit's VS1053 only works with Teensy 3.1 at 24 MHz, but not 48, 72 or 96 MHz.

Turns out, the library depends SD.begin() to reconfiguring SPI.  It also runs data transfer code from both main program & interrupt context (causing havoc if the interrupt occurs at the wrong moment).  Pretty amazing it's worked on AVR for so long, but apparently it does crash sometimes.  Faster processors increase the opportunity for the problem to strike.

Hopefully my edits from last night will fix these problems for good.

Christmas lights notes

PySerial will tell you that the following baud rates are supported:
(50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000, 2500000, 3000000, 3500000, 4000000)

Improving Arduino's Serial Monitor Performance

Today I worked on the toughest Arduino bug... keeping the serial monitor from locking up or crashing with maximum speed printing from Teensy 3.1 and Arduino Due.

Here's Technical details and mini rant about Java performance.  Hopefully this (and other good work) will lead to future Arduino versions with a serial monitor that doesn't suck.

Strain Relief

I've struggled with appropriate wire-to-board connections over the years.
 

Six Years of USB Development

Six years ago, in early Deceber 2008, I left the simple world of serial-based development behind and went native USB, releasing Teensy 1.0.  So much has happened and I've learned a lot in just 6 years.  I used to do everything by 9 pin RS-232 serial ports.  Those days seem so distant.

I'm now working on new and really awesome USB features for 2015...

Better SPI Bus Design in 3 Steps

Most Arduino SPI tutorials show this simple but poor SPI bus design:

A much better SPI bus design can prevent conflicts.  3 simple improvements are needed:

  1. Use pullup resistors on all chip select signals.

  2. Verify tri-state behavior on MISO: use a tri-state buffer chip if necessary.

  3. Protect bus access with SPI.beginTransaction(settings) and SPI.endTransaction().

Click "Read more" for details on these 3 steps.

Making nRF8001 (Bluetooth LE) and SD cards play nice together

Been working on making Adafruit_nRF8001 and the SD library work together.  Details are on this forum thread, and also this one.

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