Python
Embedded/hardware interfaces – UART, SPI, I²C, CAN, USB, JTAG, GPIO, PWM, ADC/DAC
Real-time operating systems (RTOS) or bare-metal development basics
Hardware description/validation tools – Oscilloscopes, logic analyzers, multimeters, power supplies, test rigs
Firmware build systems – Make, CMake for cross-compilation
Version control – Git (branching, sub-modules, pull-request workflow)
+20 more