Embedded hardware, interfaces and timing assumptions
Relate the program to the device
An embedded system controls or observes a particular environment through a specified processor, memory and input/output design. A microcontroller commonly integrates a processor core with peripherals, but the actual memory map, bus widths, interrupt rules and register semantics come from its documentation. Do not infer that an address means one byte or that a peripheral register behaves like ordinary RAM. Harvard and von Neumann teaching models explain instruction/data paths; modern implementations can combine caches and address spaces in ways that need the actual block diagram.
Read interfaces and supplied limits
GPIO pins can have input, output, pull, drive and alternate-function settings. A logic-high voltage level is not a promise that a pin can safely power a motor or relay. Compare the supplied per-pin, port and device-current limits, voltage tolerance and load behavior; an appropriate driver and protection may be required. This material does not authorize wiring equipment or replacing electrical safety guidance. An ADC maps an input range to codes under a stated resolution and reference; a DAC maps codes to an output under its own transfer function. Quantization, clipping, reference error and sample timing are different issues.
For a supplied ideal 12-bit ADC spanning 0 to 3.3 volts with 4096 uniform bins, bin width is 3.3/4096 volts, approximately 0.806 millivolts. A different endpoint-code convention can use another scale expression, so state the model rather than silently substituting it. A sample rate must meet the actual signal and filtering requirements; merely sampling twice a named frequency is not a complete practical anti-alias design.
Transfer and observe correctly
Polling repeatedly tests a condition; an interrupt requests attention when an enabled event occurs. Interrupt priority, masking and latency affect response. DMA can transfer data without the CPU copying every item, but completion, cache coherence, ownership and buffer lifetime still need a protocol. The C volatile qualifier can require particular compiler-visible accesses to a hardware register; it is not a mutex, an atomic read-modify-write operation or a general memory-ordering solution for concurrent threads.
UART, SPI, I 2 C and network interfaces differ in clocking, addressing, framing and electrical requirements. A schematic label alone does not establish a compatible voltage or shared-clock configuration. For timing calculations use the supplied clock, prescaler, counter width and tick definition. For example, a 1 MHz timer with a divide-by 100 prescaler advances at 10 kHz, or one tick per 100 microseconds. Overflow and off-by-one compare conventions must come from the stated device model. Test boundary values and recorded observations before concluding that a firmware change meets the intended real-world requirement.