Early last month I came across with this charlieplexing thing, something new for me, and the first that came to my mind was a clock, specifically the Wordclock. I've already built it in a simple way adressing each word using Shift registers and ULN's but sincerely I don't like it. I want a matrix, draw seconds and animations just like the original, and this method is perfect becouse it doesn't need any aditional hardware. So, I managed to build the matrix and set up the code for the 11X10 matrix, tweaking here and there everything was going just ok until I hit this wall
I'm using a Pro mini chinese. The pinout is something like this:
0 - 1 Serial communication.
2 Interrupt SQR signal RTC
3 - 13 Matrix
A4 - A5 RTC
A3 - A6 - A7 Buttons
As you can see there is only two pins left and I need four for the minute pointers.
I thought, well, maybe I can expand the matrix and integrate them and adapt the routine for display the minutes with the rest. And there's where the wall appears. Pocking through the charlieplexing code I dont find the way to do it. I mean, I want to use one pin from the analog side which is PORTC of the ATmega328p and they doesn't include it in the code.
I've use instead Pin 2 and it works but I dont want to get rid of the signal from the RTC.
So, is there any way to modified the code and make use of the PORTC, maybe just A0? I've tried but I'm lost with bitwise stuff.
Sorry if there is any mistake, English isn't my main language