But as I ran low on pin I wanted to extend my number of pin.
First I used 2 shift register (SN74HC595).
I writed a little library to use "new pin" as virtual pin and keep SevSeg library usage.
But is cause some flinkering. And the display wasn't nice looking.
Then I tested with a port expander (MCP23017).
I writed an other wrapping of these "new" pins.
And the flinkering is still there.
Do you think it is an hardware issue or more software side ?
Is it atmega, expander or library fault ?
Any suggestions, ideas, experience to share ?