Sending a struct over i2c
int isn't guaranteed to be the same size across platforms. Use fixed width integer types instead.
https://en.cppreference.com/w/cpp/types/integer
struct TransmitData
{
  int32_t a;
  int32_t b;
  int32_t c;
  int32_t d;
  float e;
  float f;
  float g;
  float h;
};