Lab 1 tasks

Work in labs/rtc/. Turn the protocol into clear C code. Keep helpers boring: a function that builds a mask should build a mask, not hide controller reads or formatting.

Requested functions

• uint8_t bit_clear(uint8_t value, uint8_t bit)
• uint8_t bit_set(uint8_t value, uint8_t bit)
• int bit_is_set(uint8_t value, uint8_t bit)
• uint8_t bit_lsb(uint16_t value)
• uint8_t bit_msb(uint16_t value)
• uint8_t bit_mask(unsigned first_bit, ...)
• int rtc_read_date(lcom_rtc_date_t *date)
• int rtc_read_time(lcom_rtc_time_t *time)

Guided gaps

• Build bit masks from bit positions and handle out-of-range bits predictably.
• End the variadic bit_mask argument list with BIT_MASK_END.
• Poll RTC_REG_A until RTC_UIP is clear.
• Keep BCD conversion small and inspectable.
• Check output pointers before writing.

Decide which helpers are exercise-only and which deserve to become reusable library code. A bcd_to_binary helper likely stays near the RTC implementation. Generic bit helpers may serve several labs if their names and behavior are precise.

IMPORTANT

Do not change RTC configuration. Interpret the mode reported by the device instead of forcing the device into the mode you prefer.

Common mistakes

Treating BCD as binary, forgetting that bit positions start at zero, returning a mask when the API asks for boolean-like output, and writing a partial structure after a failed read. Tests should lead you to these bugs if each helper stays focused.

Next: checks and references.