I’m downscaling from a Pi Pico prototype, to the simple AtMega328/AtTiny85.

Im trying to get a grasp on what is possible with slow MCU’s.

Do you have rule of thumb when guestimating, if a 8MHz single core is up to the task, without missing a ISR?

Case 1, ATMega328:

Read 2x simultaneously 9600 baud UART with bitbanging.

ACCURATELY count 1-300 pulses/second.

Send the above, with very light processing, to UART.

Realistic?

Case 2, ATTiny85:

Read 2x 100sps from a I2C ADC.

Multiply & sum readings with float!

Save value to I2C 25LC flash.

Send value as bitbanged UART.

Realistic?