I'm building a portable 8x8 LED matrix with an attiny85 and two SN74HC164s shift registers, powered off of two CR2450 coin cell batteries and having trouble determining where to put resistors in my design.
To test the SN74HC164, I connected and powered it directly to an arduino with resistors coming from the cathodes of the LEDs ( connected to the outputs of the shift register ) and nowhere else in the circuit, like shown in many tutorials.
Would there be any reason to add any resistors to the connections of the shift register, other than the outputs when powered off of the batteries or are all of the pins designed to consume only as much current as they need? I will have pins A, B and CLK connected to the I/O pins of the attiny85, VCC and GND connected directly the the batteries, with CLR connected to the voltage supply.
Do I need to limit the current through VCC and GND on the attiny85?