I'm using Arduino UNO R3 and it's pins D2&3 to communicate with LM339 (connected to car ECU) via softserial. Everything works with no LCD SHIELD (showed at serial port monitor), when I add LCD SHIELD... communication just stops.
D1 - TX
D2 - RX
A0 - KEYPAD
D4...D10 - LCD
I'm using this shield: Arduino_LCD_KeyPad_Shield__SKU__DFR0009_-DFRobot
This make no sense - pins are not interfering...
...or are there any limits that I don't know of?