Very recently I just wanted to speak some SPI to some RF IC on a breakout board. I narrowed down the quickest options to this:
* Use my UM232H (FTDI FT232H dev board) to do SPI from my Mac. Dismissed pretty quickly, since I did not feel like dealing with the drivers and FTDI library.
* Boot Linux on one of my FPGA/ARM combos and hope that the generic SPI driver also exposes itself to user space, so that I can just pipe my data on the shell using xxd -r to /dev/spi-foo or whatever. But even if the case, I had to probably at least mess with the device tree to get the I/O pins assigned (and boot Linux, and have the proper tools).
* Use the Arduino Uno that I got as a gift, but never used so far, and either use its SPI library or hope someone made a "Sketch" already that I could just paste.
In the end, the last option won out, because someone actually had made a Sketch already that I could literally just paste and run.
But that was kind of lucky. I feel like such a self-contained Forth computer that is always ready to accept some Forth (instead of having to mess with a C toolchain) could make tasks like this super quick and simple, with flexibility.
Experiences?
In the mountains of Italy, drivers give a short honk before entering a turn on a serpentine road, which usually can't be seen around. If there is no responding honk, they will take the full width of the road (making the very tight turn easier and faster). Tourist drivers have to pick up on this :)
In much of Europe oncoming cars flash their lights to warn others about dangers and (especially) speed traps or police checks, so they can slow down in time.
Here in Lithuania, flashing your warning lights (the four orange ones on the corners of the car) means thanks, for example if you let someone merge from one of the very short onramps. I've never seen this in Germany, where onramps are however much longer.
And amongst truck drivers it's pretty wide-spread to blink right to tell a following car you think it's safe for them to overtake you and blink left when you think it no longer is. At least on long roads where there are no obvious right turns. I flash them a grateful hand sign when passing their mirror.
I flash lights for oncoming traffics because of danger or police checks.
I flash warning lights (or raise right hand) for thank you. Others do as well (especially buses, when you let them out of the bus stop, since in Germany they don't have the right of passage leaving a bus stop)
I learned that truck drivers (and buses) flash left, when it's not safe to overtake.
There are also some official rules regarding bus flashing at a bus stop (right, warning). But most of drivers ignore that.