Real Time Clock: Initial Research​

A project log for PiCarts: GPIO ROM Carts

Loading from ROM cartridges plugged into the GPIO port. Just like the old days.

DustinDustin 06/12/2021 at 19:530 Comments

For a while now, I've been wanting to learn how to work with real time clock(RTC) chips. This project is a great way to get started on it. The reason I want to integrate an RTC into the carts is for running in game events after the system is turned off. I could just check the system time, but it's easy to mess with that, as well as having incorrect system time. I always loved the features of Pokemon Gold and Silver versions when they came out. Encountering different Pokemon during the day and night. I never stopped to think about how this worked when I was young. Now I understand how such features existed. With an RTC on the cart, I can duplicate in game events like that. Maybe certain enemies only come out at night, or only certain riddles can be solved with by the light of a certain moon. 

I've started looking at different RTC chips and settled on the ‎DS3231MZ/V+‎. The main problem I have with this chip is the per unit cost of $7.75. Even with bulk discounts, it's still an expensive chip. I wouldn't mind for my own use, but I want this to be an affordable board for the average hacker. I do plan to order a few of them for testing in the future and will decide if I want to integrate them or not. The chip shortage doesn't seem to be helping matters any either. 

Interfacing with this chip should be fairly simple using I2C over GPIO on the Pi 400. I haven't made too may plans for other devices to use I2C, so the interface should remain free for this chip to use. I've not gotten much done on this part of the project, but wanted to record some thoughts for future reference. Looking forward to assembling the hardware and programming for it.