Project Help: Writing values to an array, interrupts, and printing arrays

Hello, I am currently working on a project for a coding class. We are using at STM32 board and have been assigned a project that combines a lot of things we have recently been working on, including interrupts, array, ADC, etc.

The project is for us to write a code that will read the ADC in the STM32, and will put the read value into a 512 space array, that will then be printed out on our Kitty serial monitor. Individually, I haven't had issues getting the interrupts or serial monitor to work, but I'm having trouble combining the interrupts with the array. For the project, we are trying to get the interrupt to occur ever millisecond based on the hardware clock on the board. Below, I've attached the first bit of code I have written for this, but I'm honestly just not sure about it or what I need to do to move forward from this point. Any help would be appreciated.

Thing.ino (295 Bytes)

The code does something. You expect it to do something. You appear to have forgotten to tell us what either thing is.

Why do you need a 512 byte array to write a 3 digit string? 4 bytes would be sufficient.

You understand that overflow() is an interrupt service routine, right? You understand that interrupts are disabled when an ISR is running, right? You understand that Serial.print() relies on interrupts, right?