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Rongzhong Li
May 30, 2019
Edited: May 30, 2019

The logic behind calibration process

The full process of calibration in WriteInstinct.ino is:

1. You don't know where the servos are pointing at before calibration. So you don't attach the legs.


2. Upload skills, which include one "calib" posture, it's a posture with all joints at zero position. There's also a "rest" posture. Of course, you won't see the postures because you haven't attached the legs. But you can imagine that the servos will rotate when switching between the two postures.



These postures are also shown in 6.4.3 of the instruction document.

You have to enter 'Y' for saving saving skills to EEPROM. Right after that, the program will read the rest posture and rotate all servos to rest position, then shut them down to avoid vibration. Still don't attach the legs.


4. The program will ask you whether to calibrate MPU. You can enter 'n' to skip if you have already did so. You can now understand why I put Nybble to rest state before calibrating MPU. It's much easier to lay Nybble level on the table, and it won't vibrate due to the shaking of servos.


5. Now if you enter 'c', the program will read the calib posture and execute. All the servos are supposed to rotate like crazy (but they are actually transforming from rest position) until they stop at calibrate position. Then you can attach the legs one joint by one joint, perpendicular to nearby references on frames. It's easier to attach knee joints before shoulder joints.


Even if you attach legs in the direction of calibrate posture before entering 'c', the servos are actually in rest posture. Once you enter 'c', the legs are going to move, but would probably hit something in the middle. In that case, the motor will be forced to stop, and becomes a pure resistor. It will pull large current, generate heat and cause a voltage drop on the chip. That will further disturb the signals, causing more abnormal behaviors.


6. After attaching all the joints, Nybble will stand on its knees as in the calibrate state. The directions of legs won't be perfect. Use the included L-shape tuner for fine tuning each joint. You can enter 's' after calibrating each servo in case of any interruption in the process.

7. The calibration values are saved to ATmega328P's onboard EEPROM. They won't change unless some voltage shock happen to cause "bit flip" when the processor is accessing the memory location. But it's very rare. Next time you want to calibrate, you don't need to take off the legs. You can also calibrate within Nybble.ino.

2 comments10 replies
JF Marseau
Jun 29, 2019Edited: Jun 29, 2019

Hello,

I can't use 'c' command in WriteInstinct.ino , or other command (h, c9 4, d, ...).

After calibrate EEprom and MPU, I just have "Gotcha !" ...


I change the "V0_*" in "#define NyBoard_V0_2" in Instinct.h

But I have some warning before transfert to ardruino (IDE v1.8.9) :


In file included from C:\temp\OpenCat-master.20190604\OpenCat-master\Nybble\WriteInstinct\WriteInstinct.ino:31:0:

sketch\OpenCat.h:604:1: warning: narrowing conversion of '-4.5e+1' from 'double' to 'int8_t {aka signed char}' inside { } [-Wnarrowing]

 };

 ^

sketch\OpenCat.h:604:1: warning: narrowing conversion of '-4.5e+1' from 'double' to 'int8_t {aka signed char}' inside { } [-Wnarrowing]

sketch\OpenCat.h:604:1: warning: narrowing conversion of '-4.5e+1' from 'double' to 'int8_t {aka signed char}' inside { } [-Wnarrowing]

sketch\OpenCat.h:604:1: warning: narrowing conversion of '-4.5e+1' from 'double' to 'int8_t {aka signed char}' inside { } [-Wnarrowing]

sketch\OpenCat.h:604:1: warning: narrowing conversion of '4.5e+1' from 'double' to 'int8_t {aka signed char}' inside { } [-Wnarrowing]

sketch\OpenCat.h:604:1: warning: narrowing conversion of '-4.5e+1' from 'double' to 'int8_t {aka signed char}' inside { } [-Wnarrowing]

sketch\OpenCat.h:604:1: warning: narrowing conversion of '4.5e+1' from 'double' to 'int8_t {aka signed char}' inside { } [-Wnarrowing]

sketch\OpenCat.h:604:1: warning: narrowing conversion of '-4.5e+1' from 'double' to 'int8_t {aka signed char}' inside { } [-Wnarrowing]

C:\temp\OpenCat-master.20190604\OpenCat-master\Nybble\WriteInstinct\WriteInstinct.ino: In function 'void setup()':

C:\temp\OpenCat-master.20190604\OpenCat-master\Nybble\WriteInstinct\WriteInstinct.ino:231:34: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]

     motion.loadBySkillName("rest");

                                  ^

C:\temp\OpenCat-master.20190604\OpenCat-master\Nybble\WriteInstinct\WriteInstinct.ino: In function 'void loop()':

C:\temp\OpenCat-master.20190604\OpenCat-master\Nybble\WriteInstinct\WriteInstinct.ino:327:36: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]

       motion.loadBySkillName("rest");

                                    ^

C:\temp\OpenCat-master.20190604\OpenCat-master\Nybble\WriteInstinct\WriteInstinct.ino:360:41: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]

           motion.loadBySkillName("calib");

                                         ^

C:\Users\Documents\Arduino\libraries\Adafruit_PWM_Servo_Driver_Library\Adafruit_PWMServoDriver.cpp: In member function 'uint8_t Adafruit_PWMServoDriver::getPWM(uint8_t)':

C:\Users\Documents\Arduino\libraries\Adafruit_PWM_Servo_Driver_Library\Adafruit_PWMServoDriver.cpp:167:71: warning: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:

   _i2c->requestFrom((uint8_t)_i2caddr, LED0_ON_L + 4 * num, (uint8_t)4);

                                                                       ^

In file included from C:\Users\Documents\Arduino\libraries\Adafruit_PWM_Servo_Driver_Library\Adafruit_PWMServoDriver.h:27:0,

                 from C:\Users\Documents\Arduino\libraries\Adafruit_PWM_Servo_Driver_Library\Adafruit_PWMServoDriver.cpp:30:

C:\Program Files (x86)\Arduino\hardware\arduino\avr\libraries\Wire\src/Wire.h:65:13: note: candidate 1: uint8_t TwoWire::requestFrom(int, int, int)

     uint8_t requestFrom(int, int, int);

             ^

C:\Program Files (x86)\Arduino\hardware\arduino\avr\libraries\Wire\src/Wire.h:62:13: note: candidate 2: uint8_t TwoWire::requestFrom(uint8_t, uint8_t, uint8_t)

     uint8_t requestFrom(uint8_t, uint8_t, uint8_t);

             ^


0
Rongzhong Li
Jun 29, 2019

The warnings are not related to the calibration. Try connect the jumper switch SW3 between BATT and V_S.

0
JF Marseau
Jul 2, 2019

Thanks.

Nothing new.

I don't have any table with all offset ...


0
Rongzhong Li
Jul 2, 2019

You can send me a video showing how you connect the cat and send commands. Make sure the information on the screen is clear to see.

0
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leukipp
Jun 30, 2019

Watch out, I did following mistake:

- First i noticed that the Joint Map in the instruction has changed for board v0_2

- So i made my own mapping table and reverted/switched PWM pins and Joint Indices (here i made the first mistake)

- Started calibration with 'c' and servos moved all to 0 position. Everything looks good so I mounted all servos.

- I didn't do a servo by servo 'c* *' calibration and moved on to deploy Nybble.ino. (here i made the second mistake)

- Started Nybble and in rest position everything looks fine. Started a skill and boom, crazy moves. So I spend a lot of time searching for batterie issues.


After all I noticed my mapping issue and sorted it out. You just have to change the numbers in the PWM Pin row with the printed numbers on the v0_2 board, then you will have a new encoding array.


@Rongzhong Li Maybe you could update the instruction to show the different Joint Maps between v0_1 and v0_2 board!?

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Rongzhong Li
Jun 30, 2019Edited: Jul 2, 2019

You don’t need to define a new joint map yourself. It’s handled in OpenCat.h. The physical servo connection are also the same for two versions of boards. You just need to adjust the board version definition in Instinct.h, which can be considered as a configuration file.

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