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what will it do?

I'd suggest that the DMA chaining scheme could interleave the bytes: 1st pass does half, second pass does others. But DMA hardware requires address aligned buffers.

Pogo-pins... I use "fixtures" for test and programming with pogo pins. Fixture is Plexiglass pieces screwed together to form a fixed platform and a moving platform. PC board under test (UIT) gets sandwhiched between the plexiglas halves. My fixture is slightly similar to this...

Reverse how the radios are placed and connected to see if the problem follows the radio hardware or if not, the problem is the software and how it configs the radio

The RFM69 and Radiohead are a big overkiull for the app you describe, but being two-way, and having the option in Radiohead for reliable datagrams (ACK w/retransmission), allows that button-push to be assured of receipt. Low latency, like what? Narrower the channel width (channel bandwidth)...

Hmm. I've used many RFM69s and with just short-wire antennas and they provide 100m+ non-line-of-sight in 433MHz, and about 25% less in 900MHz band. Not using the sparkfun board, but rather, I used the RFM68 version, with radio+Arduino-compatible microprocessor+RealTimeClock+SPI flash data...

SDIO in 1 bit mode is faster than SPI. But SDIO shines when you implement the 4 bit mode and of course DMA on all this. Most all SDIO uses 4 bit mode. So it's wise to wire up those bits and not try to use those pins off-board. The protocol and the data are on different serial data paths to...

See post #38 on this thread https://forum.pjrc.com/threads/540-ChibiOS-RTand-FreeRTOS-for-Teensy-3-0?highlight=freertos I recall running this FreeRTOS port on T3. There are two different ports of FreeRTOS for T3, as I recall. Beware the config options: preemption and cooperative scheduler...

Why not use the existing FreeRTOS adaptation to the Teensy? There is a CMSIS RTOS port that is just API wrappers for FreeRTOS. The CMSIS RTOS wrappers add no value other that vague RTOS independence which, in the end, won't be independent and/or isn't essential, since FreeRTOS is stable and...

Hardware debounce often reduces but doesn't eliminate the false detections. There are several good ways to do this in software (firmware). My favorite is: Most MCU apps have a recurring timer interrupt, say 100 or 1,000 Hz. In the ISR for that, you read the switch bit(s) from GPIO. If a switch...

Internal pull-ups are weak.. like 30-40K.

@bigpilot... not wanting to use Teensyduino libraries but rather code for direct hardware access? Hand-near-wire = interrupts is simply this: That GPIO pin is an input and there is no chip-internal or external pull-up resistor. Thus, the pin is "floating" and is therefore high impedance. This...

IMO, it's quite probable that Oracle will dump Java into the public domain as they did SUN OS. It's not a revenue generator, or is quite the opposite. That and HTML5 and AJAX and so on might relegate Java to disuse. I'll draw a distinction between a browser-based IDE and a Web server based...

Most often, unused pins are programmed early in startup as GPIO Input, no pull-up. But some vendors recommend "analog" input. The internal pull-ups, if enabled, are on the order or 40K.

Here's current transformer I'm using (5A for gas dryer on/off and same for washer). 1V peak to peak sine wave at full load. Resistor divider on one leg of signal to bias up to mid-range of ADC. Other lead from transformer goes to ADC or GPIO. Current transformer clips over one lead of extension...

I'd expect Microchip/MPLAB for PIC to require Windows 3. :eek:

need proper driver with block buffered I/O.

Not Zigbee unless you must have a mesh/repeater. And for a potable water tank, you need a super reliable data link with a supervision mode and lost-link alarms. My brother struggled with this as the prez of a small private water company (20 subs). He had a leased pair of wires from ma Bell for...

I agree on Digitstump Oak. I have it and Particle IO and various ESP8266 boards. mbed started the browser IDE for embedded MCUs but they ran out of motivation or life moved on. "The" browser IDE plugin is ATOM, and add-ons to it (including the pre-alpha Platform IO may do the same, as another...

based on my extensive use of ST's HAL for 8 or IO devices, in complex apps, I have to disagree with the generalization. But this is Not applicable to current Teensy and next.

I agree with not preferring web based MCU programming. BUT, forf modest sized programs, and for people younger than we, I think it's a good thing. Improves access to a rather complicated set of tools for the casual/new users.

Re your question on IDEs.... On Windows, I very much prefer VIsual Micro with Visual Studio Community 2015. Both are free. High quality. Teensy specific choice in board targets. Software debug low cost option. For $90 there's Visual GDB which is a step up from the Visual Micro. And has...

ex·pert ˈekˌspurt noun 1. Past tense of a drip

30 gauge! Not teflon insulation - requires special razor blade stripper

have an LED blinky "I'm alive" on the Teensy? What does ("no /dev/ttyACM0" stuff)" mean? Is that an error displayed on the RPi? I have an RPi connected to an XBee via fast UART and don't have faults with the serial. When you say "connection" between the Teensy and RPi, is there a certain...

That's the interview I mentioned yesterday (but couldn't find the URL). Also touches on the platformIO "IDE" (seems a mess). Codebender not mentioned. Both not for profit.

I can't find the link to the interview done by Elliot Williams. I think it was at this most recent hackaday conference. Both Companies exhibited? The interview touched on the legal battle status (no news, stalemate) and their new push to promote ST *and* Intel's Quark and not Atmel/MCHP. And...

Does the unusual Arduino build process cause the linker to include functions that are explicitly defined via function prototypes, but those functions are not referenced/called in the actual code?

Interview... Great words of wisdom!

Adding to Paul's comments... since you're adding a chip or more, you could greatly reduce the risk by multiplexing the MOSI/MISO/Clock to go to/from only the connection affiliated with the corresponding chip select. If the wires are very short, like 6 inches, you might get away with a wired...

Is Arduino really going towards PlatformIO and the two other as yet not integrated dependencies it has? As was said in Hackaday interview? Will that change the build concept?

+1 Tools should be used efficiently and should not be inferior or a big time-distraction. The bifurcated Arduino world is enamored with Platformio (.org), IDE. It's github's Atom browser editor + user-integrated additional software = IDE...

There are several manufacturers of the NAND Flash controller chip (die) within SD cards. Some are better than others, esp. at error correction code (ECC) processing which is the Achilles heel of MLC NAND flash. COmputations for ECC for 16GB and up are rather complex. The retail brand names...

Not sure about GCC (Arduino) using DSP instructions, or by default, versus other compilers like IAR, Keil. If you use floating point, the current Teensy's don't have that ARM feature. Next one will. May not matter to your app. Don't most such transforms use a lot of transcendental functions...

10m range is an issue?

re post #14.. could this be an idiosyncrasy of the Arduino non-standard preprocessor? ANSI C permits the [] syntax.

You can simply use all C for your work, yes? And either no C++, or use someone's library in C++, but write a C wrapper so your C code can use wrappers to call C++ functions. The wrappers are easy to do. And if you can avoid using C++ in your app, things will be SO much easier. The horrors of...

ah, yes. My comment was more aimed at less experienced people. Do you know about this: What does GCC default to for string literals? Like char text[] = "hello world"; or a better example printf("%d hello world\n", millis()); Would both default to having the const attribute? In some C...

With the initializer (the constants enclosed with curly braces), you need not hard code the array size, i.e., 36929 in this case. You just use empty brackets like []. I have a program that has several 46KB images in the compile time code. As big lists of hex numbers where those numbers came...

Murphy was an optimist. :p

Rare to find exception handling in a modest RAM-size MCU. Compiler warnings can be disabled but I suggest leaving them on since some can indicate must-fix issues. I'd beware using New or malloc() or free() in small RAM MCUs. Or overuse of the heap in general, or the String class...

Or, if your code goes berzerk (wild jump, stack corruption, etc., or uses a library such that the library goes berzerk, the Teensy can get into a state where it cannot respond to a software-invoked download. So the PROGRAM Button forces the download to start and preempts the berzerk program...

Wow. How'd that happen?

if pressed, you could omit all floating point in calculations and I/O, and use a fixed point library instead, for real numbers. Much faster, too.

Be sure to read up and know when/if to use the SPI Transactions library from PJRC.

I may have misunderstood... we're talking about Teensy, not Teensy 3, right? And Teensy++ 2 allows for a 32768MHz crystal, per its schematic (scroll down to it). Yes, that grey-out crystal on the Teensy++ 2 schematic would be added. Or you wire up an external RTC chip as described on PJRC's...

Four GPIO bits fed to a 4 to 16 logic level decoder chip. Now you have 16 chip select signals, all mutually exclusive. The switching time would be super fast. That decoder chip needs to have an Enable which you set true after changing the 4 bit code sent to the GPIO bits. Then set the Enable...

On the schematic, you'll note the optionally installed 32768 crystal on pins 19,20 of the MCU. https://www.pjrc.com/teensy/schematic.html Many MCUs of varied type have that option for the crystal. If installed, software can enable the oscillator controlled by the 32768 crystal and utilize the...

@xxxajk From Wikipedia - - Software usable only by the author is unfortunate if it is publicized.

Opinion alert... I'll take a pass on Intel's schizophrenic CurieQuark - with its x86 core that has no floating point and a 2nd core that's not ARM based. This schizophrenia is Intel Marketing driving the ship, paranoid about the sea state shift to ARM. The ARM world, with lots and lots of...