hi I was so much inspired by your project and decided to make one myself I 3d printed the parts I followed wiring diagram given below similar to your's
I used ardiuno uno instead of nano,and a lab bench power supply instead of battery ,also I didnt used infrared receiver,buzzer and raspberry pi since i want to test it with serial communication through usb initially.I wired up the servo's in correct manner and followed the calibration procedure
1)First i uploaded WriteInstinct and open serial monitor typed y to reset the joints make the arms 90 degree and fitted the servo arm but i cant calibarate mpu module it is showing me image below
But if press c command in serial monitor i can see the index and offset value and my servo are responding if i change offset values with commands(say c0 20,etc) after that i saved the calibration
if i try r command or k balance it showing wrong key! but it shut down servos for d command then i tried to upload the Nybble code .After uploading some value keep on displaying after some strings like in image, there is no response for the any command (i have tried k sit,k balance,rest) .how can fix it.