Genuinely curious, what kinds of projects are better suited to a Teensy than an Arduino, ESP32 or some form of Raspberry Pi?
Is the main advantage the pin count?
Is the main advantage the pin count?
Now that Arduino is running an ESP32 or ARM chip or has FPGA acceleration and such I'd say the difference is mostly just size. I do think some of the core libraries for the Teensy are better written though, the Arduino authors don't seem to focus as much as Paul does on optimizations. Paul also frequently posts in the forums to respond to questions, which is unusual in my experience.
Edit: In response to the Raspberry Pi, it's just a totally different beast. The Teensy is probably not well suited to run much of an OS (nor is the Arduino). Both are better suited to things that require more pins available; embedded controllers rather than computer substitutes.
I recently used a Teensy for exactly the reasons you gave, but I'm not familiar with Arduino's with ARM or FPGA. That sounds very interesting, do you have some links where we can learn more?
The Arduino Due has been around for probably seven years and runs on ARM. There are many other versions now that are all ARM. The FPGA coprocessor one... hmm, I don't see it so maybe I just read it in the news or got confused by the Portenta that is supposed to be released about now.
The ESP32 one... I thought Arduino was moving to that for the RF capabilities but might be wrong, I can't find one for that either anymore. I know for sure you can get a ESP32 dev board and program it with the Arduino IDE and their Arduino-IDF libraries compile nearly Arduino-identical code with a few limitations (relative to the Teensy, which I think is basically perfect library API duplication).
The "FPGA acceleration", on the other hand, is pretty limited. Arduino has one board -- the MKR Vidor 4000 [1] -- with an onboard FPGA. The FPGA can be configured with one of a couple prepackaged bitstreams to add I/Os or perform some specific video processing tasks; it does not accelerate processing on the Arduino MCU. The documentation for the board is minimal, and support for generating your own bitstreams is basically nonexistent. The whole thing has a half-baked feel to it; I'd avoid it.
I await the day when I can be like "nah, pin 2 will be a 16-bit 10MHz PWM output controlled by this register and pin 7 will be a frequency counter" and then access that with code on the microcontroller as if it was a built in peripheral.
I'm kind of skeptical I'll ever really get into FPGAs otherwise, my use case for them is always so simple, at the level of... well... PWM outputs and PID loops. But a microcontroller is fast enough for most PID loops so really to me the advantage is customizable function-pin mappings. I can't imagine trying to implement something like an ethernet stack on an FPGA though, although I guess you can run DOOM on one so maybe there will be a compiler from C++ to FPGA somehow that's not comically bad. ;-)
http://papilio.cc/index.php?n=Papilio.PapilioDUOHardwareGuid...
edit: yep...still for sale http://store.gadgetfactory.net/fpga/
In practice using this library/ecosystem/whatever is different enough from "normal" embedded C/C++ libraries that to me at least to me it does feel like a different language.
I think most people call it a language out of ignorance or laziness though.
I just write standard C++ or C code and it compiles fine. Hard to complain about that too much if I don't care to use the extra features. You can just access registers directly even if you use the Arduino IDE and configure things yourself if you want.
But yeah, I'd personally use visual studio code if I wasn't going to want to use the arduino libraries anyway. It's not a great editor. VS Code probably isn't that great either, but it's good enough for the little coding I do (I mostly design circuit boards that frequently use these little boards as brains).
If you don't care about premade environments then yeah, it's mainly about which pins and embedded peripheral the board supports. Pin count is not everything, nobody wants to bitbang USB or even high-speed SPI. For instance I see that this teensy board supports up to 18 analog inputs when Arduino supports between 6 and 15 according to this: https://www.arduino.cc/reference/en/language/functions/analo...
Basically the choice of controller should be the last step in your design: first thing about your inputs and outputs, then find a controller with suitable I/O and processing power (and preferably with standard header spacing).
RPi is more like a mini-computer than a controller, it's a lot more powerful and comes with massively more overhead. You program something like a teensy on "bare metal" with only a very minimal runtime. On an RPi you'd typically run a full blown OS. That opens up many possibilities but it's also generally more expensive and more power hungry. If you just want to drive 5 GPIOs it's completely overkill.
It would be nice if there was a Teensy board with analog audio output, though.
What I'd like is a Teensy board with SERIOUS analog output that still works with my Chord Organ firmware. Like 192k (or indeed 96k) and 24 bit… but I could get a lot of use out of even low-bit at elevated sample rates, because one of my options for coding stuff on the firmware and Tom's eurorack module hardware is using the Teensy's library to produce multiple square waves.
If I'm outputting square waves I can use almost arbitrarily low-bit word length, but high sample rate will greatly reduce aliasing, and not just for high frequencies. The Teensy raw audio stuff has a characteristic grunginess on squares and saws that is mostly or entirely about aliasing.
[1] https://www.nxp.com/products/audio/audio-converters/ultra-lo...
Also exist a neat workflow where you design your keyb on http://www.keyboard-layout-editor.com and then import it on https://kbfirmware.com and you get your keyb up and running very fast.
But it's also very encouraging that on the Teensy the issue was identified and a solution provided so quickly.
On the responsiveness note, I found a typo in the ESP32 datasheet and reported it to them through the forum. They responded very quickly and noted that it was indeed a typo (their chip as described didn't have a ground pin) and promised to fix it.
So on speed that's great. But their most recent datasheet had the same typo so...
IMO, the Teensy boards have historically not only completely duplicated the functionality of most Arduino boards (including supporting the Arduino IDE), they've also provided additional features/peripherals not present on most Arduino boards. (Increased RAM, flash, CPU, peripherals like onboard CAN controllers, ability to enumerate as a variety of USB devices, and yes, more available pins)
I've also felt that that the Arduino boards are engineered (physically and feature-wise) to sell their branded daughtercards (Arduino "shields"). This is not necessarily a bad thing for beginner-level classroom environments. However, if you're looking to do something practical, it's a lot easier to throw a Teensy into a breadboard.
The Teensy also has a DSP on board which can be useful in many applications, from music to signal processing. Here's a SDR radio built around a Teensy some years back. http://theradioboard.com/rb/viewtopic.php?f=4&t=6641 Does anyone know of any kits like that around?
I can see why the Raspberry might not be a good replacement for Teensy - power hungry (ESP32/STM32 have fantastic ULP/Deep sleep) and/or form factor.
> pin count?
maybe but there are ultra cheap analog and digital multiplexers available.
It was really easy to setup and start pushing code to it
Automatic window blind opener? Teensy 2.0 if you like AVR, Teensy LC if you like ARM.
Camera watching your 3d printer using computer vision to detect if it catches on fire? Raspberry Pi.
Basically, if you want an Arduino that's roughly a thousand times faster, you want a Teensy 4.
In my experience, all projects I would do with an Arduino. Thus far, it's just been LED stuff. On Arduino I very quickly ran out of resources, then had to redo my entire project wiring to switch over to a Teensy.
firmware does not have the overhead of a host OS. super low power modes, instant sleep/wake, exact control of instructions/clock, far fewer security issues.
Teensy and ESP32 are just souped up Arduinos.
Cheaper, more powerful, more feature-rich Arduinos, if you squint. I'm not sure why you would actually use an Arduino™ unless they've really improved their lineup since I last looked.
The clones are so much less expensive than the official Arduinos that there's no comparison. Even the versions that Adafruit makes that IMHO, improve the design cost less than the official arduinos. So it's not a surprise that the Chinese clones will be dirt cheap. I'm not complaining though. I have a board where the Nano (clone) itself is by far the cheapest "chip" in the BOM. Precision analog devices are expensive and my 50 or so boards sold each year can't compete with the Shenzen manufacturers' economies of scale.