Not long after I posted the project log "The anatomy of feature creep", @Xasin  posted a comment suggesting that I try something other than an AVR chip for this project. For example, many ARM chips have a built-in USB peripheral and bootloader, which would remove some of the complexity & hardware from the previous plan.

I have been looking for an excuse to play with ARM chips and this was all I needed to go foraging down the path to learn everything I could. ARM is very different than AVR and I spent several days with my head spinning trying to figure everything out.

This may have removed some hardware from the design, but replaced it with some new mental gymnastics.

Which Chip?

I started with the STM32F070RB (via a Nucleo-64 dev board). From what I could find, the STM32 line of chips has a great following and quite a bit of online support.  I've been really enjoying playing with this chip, so far. The only problem is that it doesn't have an integrated EEPROM; which the final device will need.

This week I'll be giving the STM32L053R8 a try. It looks very similar to the F070, and has an EEPROM built-in. If it works, it'll have everything I need in a single chip.

The original suggestion from @Xasin was to use a ESP32 Pico for this project and I'll be giving that dev board a try soon. This chip would give the project wifi and bluetooth, however, I'd have to add a UART/USB bridge and an external EEPROM chip.

Software Stack

Here are the tools I'm using for ARM development:

• GCC toolchain
• VS Code IDE
• ChibiOS RTOS & HAL

IDE

I tried to use Eclipse, I really did. My problem is, I really f***ing hate eclipse. It's large and clunky and I'm just used to more streamlined IDEs. When I use eclipse, I feel like I spend more time dealing with the IDE than actually working.

I read about people using Visual Studio Code and decided to give it a try. Once I got it up and running I was floored by the level of integration it has with ARM development through the plugins. Everything from compiling & flashing to debugging & stepping through the execution of the program is all in the IDE.

ChibiOS

This part is probably complete overkill. Do I really need a RTOS for fading some LEDs? Probably not...but, it does make fading without blocking a hell of a lot nicer than traditional methods. Also, the HAL it includes for interfacing chips is quite nice.

What's Next?

After I prototype a little more with the dev boards, I'll decide on a chip and send off another order to OSH Park for more purple PCBs.