You might probably involve with Crystal Real Time Clock development project before, but have you ever done it with the system interrupts?
If you don’t know what the system interrupts for, it’s a process that stops a microprocessor/microcontroller from what it is doing. By doing this step, it will enable you to do other task instead of the previous one. Please allow me to give you an example here. Let’s say that the main program is running and performing some function in a circuit, suddenly an interrupt applying into the program. It caused the program halted immediately. In the same time, another routine is carried out. When the routine had finished, the processor goes back to main routine again! Sounds simple, isn’t it?
For this project, you’ll have to use the USB NerdKits, which is already included a 14.7456MHz crystal. The main purpose of this feature is to clock each instruction that microcontroller executes. Meanwhile, we still can use the same crystal to keep track of “wall time”, either it’s measured in seconds, minutes, hours, days and so on.
Well, although it might sounds a little bit hard to develop this Crystal Real Time Clock, but it’s almost the same as the other, except it’s involving the system interrupt! So, let’s go and build it right now…