Using AVR microcontrollers.
The classic easy to interface and quite self contained 8-bit controller.
Chips are available from china and local shops for local people. If you can order from a large vendor, they probably carry AVR. Boards are also common. Especially things labeled as somethingduino. They can generally be flashed regularly as well.
USB ASP clones are incredibly cheap. RPi and other GPIO happy computers may be able to use essentially no hardware. A "BSD" adapter for PC parallel ports is essentially four resistors for protection and works great. Bus Pirate is one more (slow!) option.
- LC-tech STM32 and AVR testing
- My old ATMega8515 board
- Minimal target boards
- Attiny13 SOIC on adapter, DIP as is
The avr-gcc set and either uisp or avrdude work just great on most platforms.
Projects, examples, tutorials etc are abundant.