Yeah, I didn't know that existed but I created my own make environment a while back. My arduinos have been gathering dust for about 5 years, ever since I discovered the ST nucleo64 line ... 80MHz, 1M flash, 256K sram, 4 UARTs, 4 SPI, 4 I2C, 20+ GPIO, 4 ADCs for under US$15 ... I pretty much stopped using Arduino everything.
Me, too. But now that I've found the Teensy 3.6, it's my new goto. It's too expensive, but it has all the power. Also, I've been doing embedded for over 20 years and I'm starting to appreciate the simplicity of Arduino. It does get most of the job done. And when I had to modify the drivres, I was able to write completely low-level code. Only walls I've run into are tweaking the linker file. I haven't been able to locate that :(
