Hello, I want to make module display to work(2 numbers each with 7 leds) and 1 for dot . This are 15 pins + 3 pins for buttons (start, "+" and "-"). I need another one for relay, but I have only a6 , a7 , tx and rx pins . Can I use any of them for digital input or for powering led ?
Sorry for my bad English.
I using arduino Nano atmega328
A6, A7, input yes. analogRead() and compare to <300, > 600 for example.
Rx, Tx can be used also. If as inputs may interfere with serial downloads if driver cannot be tristated.
Go slightly bigger, '1284P, 32 total IO. 24 digital, 8 digital/analog input. Use FTDI Basic plugged on for serial downloads.
http://www.crossroadsfencing.com/BobuinoRev17/
Or use some shift register or port expander. 74HC595 should work well.
Thank you CrossRoads, I will use a6 and a7 for buttons.