Microcontroller Questions

Had a short interview on microcontrollers, I was pretty rusty…

1) How to share information between multiple IC’s?

I interpreted this question as testing my knowledge of working between different time domains, and whipped up a response using a shared memory bank and inverting the write enables of the connected IC’s.

Turns out they were asking for more high level stuff…like using an UART, SPI, I2C, CAN and DMA. DMA seems to be a really popular question in embedded and digital design.

DMA: “This feature is useful any time the CPU cannot keep up with the rate of data transfer, or where the CPU needs to perform useful work while waiting for a relatively slow I/O data transfer.”

2) How to get a slower clock signal from a source clock? Use interrupts on fixed counts of the faster clock.

3) How to generate a PWM signal…output high on (duty_cycle)*period, the rest output low.

4) Talk about using data structures on a micro vs. a PC…
Ex. Storing a value table to generate sine waves. Pre-store strings. Use shifts instead of divisions, etc

4) An ADC is sampling a signal, how do you sync the ADC’s clock to the source’s?
-Easy case: You have access to the signal clock, use the same clock for ADC.
-The question was then modified to use a sinusoidal signal, this makes it easier…use either peak-detector, or count the time between positive/negative crossings to find the period.
-Quadrature sampling…use two reference signals offset by 90 degrees.
-Phase-lock loop? Not familiar with that at all 😦

5) Different micro platforms…PIC, Arduino/Atmega, Microchip, 8051, etc.

Overall, need to be a bit more polished and articulate in explaining technical concepts.


About collapsedwavefn

I have a lot of thoughts. Some of them I'd like to share.
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