I’ve been doing a lot of development on Arm based systems with embedded Linux. These workhorses just compute and sip power. I’ve developed on both the 32bit and 64bit versions and with Buildroot and some proper DTB setup you can have all the available peripherals nicely bootstrapped by the time the shell is loaded.
NORDIC NRF 51/52
Nordic was first out of the gate with a solid(ish) working Arm Cortext m4 based BLE system on a chip. I’ve made extensive use of Nordic’s offerings during my time at VirTra (Starting with SDK 9). Each SDK has progressively gotten better and almost always addresses hardware issues on the silicon (I’m looking at you USB and TWI). None the less, I’ve integrated pressure sensors, motion sensors, battery monitors, and even microphones. Nordic has an excellent configuration methodology allowing pin by pin configuration and routing. In addition, they added support for Zigbee via their “Soft Device” system. A soft device is essentially a hardware configuration for the on-board receiver and transmitter that allows NRF devices to meet specific standards such as BLE 4.0, BLE 5.0, and now Zigbee! Heck, it’s even got an implementation of Zephyr RTOS now. My biggest complaint regarding the NRF series is that they are not designed like a traditional micro-controller, so unfortunately care must be taken by your EE to assure proper brown-out behavior and at immediate power on as many of the pins can have transients before their proper configuration state is asserted. I leverage VSCode for my NRF development, it has the ability to debug using OpenOCD. You can see some of the devices I brought to life here. Most of these are weapon magazines and peripherals.
Solid little 8-bit processor series. These devices are ideal for low cost, low power products. Using C and Atmel’s device headers and *poof* you’re off to the races. The assembler is straight forward but I can’t recall in any recent projects the need for going that low level, nor have any applications come close to running out of code space. I won’t say the same for RAM, as depending on the version and the application things could get tight. Atmel Studio was also nice, I see that Microchip is slowly phasing it out — too bad — the new MPLab is a decent cross-platform environment. I may have to look into some VSCode integration so I can unify my embedded environments.
Marketed as network processors these Harvard Architecture (Separated program and data) base RISC devices were excellent at AES encryption and were the basis for my smart card cashless system. Their GNU based compiler and debugger worked fine although debugging was not as polished as it is today.
MICROCHIP 16x SERIES
Fast RISC based processors. They are very cost-effective and low power. At the time, not the friendliest beasts but once you got your head around the banking and the accumulator and bit flags they could get a lot done!