Microcontroller RTC Functionality

[NicoleMaggard]

Introduction

Flight Controller V4B will feature an RTC: RV-3028-C7
The intention of utilizing this RTC will be to enable Satellite Real-Time Telemetry! The design intent of utilizing the real time clock is to do the math of the time it takes from ground transmission to satellite reception and calculate the distance knowing the speed of light. With the implementation of multiple ground stations at known separation distances, the satellite may then be able to calculate its position.

The RTC Idea

The RTC will be powered with supercapacitors through launch but the registers only track time with a resolution of 1 Hz. A function will be needed to calibrate the Microcontroller time which will tick on a ns-ms basis (and will be useful to determining the time difference in transmission). The main idea is that the microcontroller will require a function to synchronize with the first tick of the RTC. On this first tick after an update to the "seconds" register the microcontroller should then synchronize with the RTC. The I2C Fast Mode should be used to continuously poll the RTC until the change in time is no longer "unexpected." The Microcontroller should expect the time on the RTC to update after a certain tick, and if the RTC updates the register before or after the expected tick, the microcontroller should readjust its time and wait for the next second to check calibration.