The shield for Ferduino Mega has full isolation too.
As you told the Tentacle can work with UART, there any special reason to use I2C instead UART?
As I can see in documentation and sample code for 1 shield only this pins are needed.
SoftwareSerial sSerial(11, 10); // RX, TX - Name the software serial library sftSerial (this cannot be omitted)
int s0 = 7; // Tentacle uses pin 7 for multiplexer control S0
int s1 = 6; // Tentacle uses pin 6 for multiplexer control S1
int enable_1 = 5; // Tentacle uses pin 5 to control pin E on shield 1
To make it work without change the code you can wire this pins like this:
10 -11 to 15 - 14 (RX3 and TX3);
6 - 7 to 17 - 16 (S1 and S0);
Pin 5 to GND or 5V I don't know what's default status to use only 1 shield maybe Patrick can help.
And don't forget to change jumpers for this position:
-------------------------------- Last edited Mon Mar 20, 2017 1:21 pm --------------------------------
Use this code for tests:
https://create.arduino.cc/editor/Fernan ... 4c/preview