HI Jeff, i work in UAV project with nrf52, i use a gy+-87 as motion's sensor . i have update your library of mpu 6050 for nrf 51 to nrf52 and it worked well based on the i2cdev library of nrf. i wrote a similar lirary for the hmc5883 inspired from yours for adruino, but i have some problem, the first that when i set a bypass to MPU6050, it seems that didnt work because i don't receve any data from the mag sensor, second when i try a lonely mag sensor hmc5883, i get data but the function of set gain and set mode seems didnt work because the when i receive data , all parameters of the sensor are the default parameters.
can u take an eye please in my library and try to fixed the problem because i see that all the code was right
mpu6500.c
mpu6500.h
i2cdev.c
i2cdev.h
main.c