Arduino with SC16IS750

Projects Programming
6

Okay, I have added some 4.7k resistors and get this on my serial monitor from the Arduino 2 where RX/TX is connected:

⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A⸮B⸮C⸮A

And on the serial monitor from the Arduino 1 where I2C is connected I get only an output if the TX/RX on my Arduino 2 is not connected:

A = -26963
A = -26963
A = -1749
B = -212
B = -19867
B = 8212
A = -256
B = -21179
B = -31702
A = -14940
A = 23060
A = 5209
C = 17750
A = 5209
C = -39
C = 5209
A = 5209
C = 5209
A = 23060
A = 17750
A = -2983
A = 5209
C = 5209
A = 5209
A = 23060
A = -14940
A = 23060
A = -14940
A = 23060
A = 23060
B = 17664
A = -20014
B = 17664
A = 23072
B = 25889
B = 22921
A = -13403
B = 18720
B = -28160
B = 18577
A = -20016
B = 4096
B = -20480
A = 20736
B = 5120
A = 5120
B = -28272
B = 22893
B = 25741
B = 25805
B = 25701
B = 25877
B = -13771
B = -27568
B = 19093
B = -23552
A = -30126
A = -20014
B = 18688
A = -256
B = 5120
A = -27055
A = -27819
B = 25957
B = 26005
B = 25925
B = 25965
A = 5193
B = 25933
B = 25965
C = -27371
B = -14059
C = 5209
A = 5209
A = 17109

But both outputs are not as expected. What is wrong with the code?