Here’s what the little Skunkworks from Jim N5IB in collaboration witih W0EB and W2CTX has been up to!
Jim says he has “A wee PC board that accepts a Teensy 3.5 or 3.6 processor, then plugs into the space that would have been occupied by a NANO”.
Corresponding I/O lines are routed to maintain compatibility with the uBITX. Since the Teensy has a RTC (real time clock) there’s a spot for its backup battery.
In principle, the adapter could be used to plug in a Teensy anywhere a NANO used to live. On a stock Raduino (you would have to remove the NANO and socket the space). On an enhanced Raduino, such as the RadI2Cino (developed by N5IB/W0EB and W2CTX) it is simply a matter of inserting the plug.
The Teensy brings lots more memory, more I/O lines including lots of analogue ports, an on-card microSD slot, and of course a Real Time Clock.
The Teensy 3.5 runs on 3-6 volts, with 3.3V logic, but has 5 V tolerant digital inputs. The Teensy 3.6 also runs on 3-6 V, but its logic is 3.3V only. It is faster and has more memory than the Teensy 3.5.
Prototype boards are in hand and will be beta tested within the next few days. Firmware portability is of course the thing that must be confirmed.
Jim promises to keep us up to date.
N5IB reports, “ALPS, a maker of rotary encoders, recommends 10K pullup to Vcc, then 10K in series with 0.01 uF to ground. The internal pullup in the ATMega is loosely specified – somewhere in the tens of K, max 50K.
Jim Sheldon W0EB responded with, “This settled the really cheap and modified (to take the detents out) encoder on the test set right down. Tuning is extremely smooth and I don’t notice ANY digits showing up and then backing up again as it did before.
“I can highly recommend adding a 10K external pullup to both the encoder A and B inputs as well as an additional 10K in series with .1uF capacitor to ground on both the A and B inputs to the Raduino card.
“It was a nice surprise addition and I won’t leave them out again.”
Hans G0UPL responds, “Debouncing and pullups are also possible in the firmware. This is the method I use in the QRP Labs kits like QCX http://qrp-labs.com/qcx – look at the schematic: no pull-ups, no RC-debounce. Saves 6 components (4 resistors, 2 capacitors). It’s not important in a one-off build or modification but in a kit where you are trying to optimise cost, every resistor helps! The firmware method also gives you more control over how you do your debounce. I prefer the state-machine approach to rotary encoder handling, it implicitly debounces without involving any time constants.”