We$$re receiving data over a UART without a DMA, so a simple RX shift register is getting individual bits clocked into the receiver at the link$$s baud rate. When a full byte arrives, we get an interrupt and must read the register before the next byte starts getting clocked in$,$ or we$$ll get an overrun error from the UART. We also can$$t immediately process the byte; we need to save it for later. Eventually, the firmware application will get around to asking how many bytes have arrived and, if $$enough$$ are present, will read them out and process them.

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Please sketch out the API for the data structure you would use to accumulate these received bytes from the UART for later retrieval. Assume that there$$s a UART RX interrupt that uses your data structure$$s API to say $$hey$,$ I just got a byte from over there, please hang on to it for me$.$

What does the data structure$$s API look like for storing newly$-$received bytes from the ISR?

What does the data structure$$s API look like, that the application uses to retrieve a buffer of N bytes?

If there$$s memory involved, who provides it to the data structure?

If you have time, try implementing it$!$

If you have more time, try changing it from receiving one byte at a time $($shift register$)$ to receiving N bytes at a time $($DMA$).$