Assembling Instructions

(1) The ultrasound sensor connects to D8, D9, D10, GND. At this moment the sensing code has not been integrated into Nybble.ino. The LED is optional to indicate the sensor's status, and will flash according to the distance once in function. It can also be programed to be decorative dynamic colors.

(2) Yes, I can feel your frustration and am very sorry for that. I'm adding more details to the tutorial every day. For the screws, I just listed them and display them in different colors. The last animation in the tutorial shows how it will look like.

(3) The two videos (body and battery) are relatively independent. In the battery video I show only the belly piece for clarity. I just swapped their orders as you wish.

(4) The assembling of the new battery holder will be a scene during a long animation (I'm making it right now. It's like directing a long-take film clip). I just added a screenshot to show the correct holes before uploading the full animation.

(5) The dents design came before the rubber. It's intended to provide sufficient friction even without the rubber toe. So I'd keep it.

Hope the above answers your question! And please keep asking questions so I can add more bits to enrich the tutorial.

The main body animation has been updated: https://youtu.be/B8N2KAf8p28

Quick answer to your questions:

- I'm uncertain what the intent was for mounting the tail.

The tail is used for posturing and recovering. It's half constrained to allow pitch rotation.

- I don't know what the 5 small hexagons and 1 small circle are used for.

They are optional nuts if you want to mount some board on with self tapping screws. A circuit board usually has 4 mounting holes but I included one extra. The small circle on the tip of shank is for calibration reference.

- It would be really helpful to have instructions on preparing it for use with a Pi.

The included 2x5 female socket is the only thing you need to solder for Pi. The animation in the post shows the configuration for Pi.

- I'm thinking of remapping the joint indices. The cable length for the rear shoulder joints is a very tight fit.

Tight but works. I also noticed that and your remapping should work. In my new servo orders I increased the wire length by 1cm.

It's all up to you to change the joint mapping. Remember to changed it if you pull my future updates though.

- With the RPi configuration you've posted, the header for connecting to the FTDI chip is unreachable.

You are right. It's supposed to be bent towards another side of the board, opposite to the NyBoard alone configuration. The animation in the post shows the adjustment for Pi. I also mentioned it in this new tutorial video, at 2:00. I showed the Pi configuration under multiple occasions. Maybe I should group them in one post and have more close-up photos.

I love the tutorial you shared. It allows sectional comments in a long document. Do you by any chance know how it's done? Or I could split this instruction to multiple posts. The TOC of OpenCat Wiki shows my intent of the chapter plan. It will be like a book or graduate thesis.

I'm out for a conference and will return on Saturday. I'll add more bits during the gaps of meetings.

@Rongzhong Li Thanks for the rapid response during your travel! My question about the tail was not about what it's used for, but about how to mount it.

Thank you for the new video. I think you posted that after I ran into my trouble. It's great to see such rapid progress in getting everything together.

The tutorial I posted is by Dozuki. It's one of the best sites I've seen for maintaining instructions such as these. You can always do something similar via a wiki, but I really like how these are done. Each image you can click on to get the high resolution version, which is sometimes incredibly helpful with small electronics projects. Here's their pricing plan for open source projects. The lowest tier one is free, but will have some ad content. https://www.dozuki.com/Document/qJj2gAd2bhFZocYC/.pdf

I'm currently having trouble with the calibration using WriteInstinct.ino. It isn't moving to the calibration position. I'm going to add some debug lines to the code to troubleshoot on my own, though. I've tested each servo operation through the driver using Adafruit's test servo. BTW, I don't understand the pins definition in your servo test module. It doesn't look like it corresponds to the correct pinout of Nybble.

Great job so far. I know it probably seems like a lot of growing pains, but these early issues will work out and make a better experience for the rest of your users in the near future!

First check, have you dialed the I2C switch (SW2) to "Ar" meaning Arduino? If it doesn't solve the problem, download the new version code. In my updated Nybble.ino, I increased the delay on line 267 to allow more time for connecting.

There's a test code for MPU on GitHub. You can validate whether the module is connected and working. If the test code works alone, but not inside Nybble.ino, comment out the do while loop from line 263 as:

//do  
{ PTLF("Connecting MPU6050...");    
mpu.initialize(); 
delay(2000); // verify connection PTLF("Testing connections..."); PTL(mpu.testConnection() ? F("MPU successful") : F("MPU failed"));  } //while (!mpu.testConnection());

Adding photos and screenshots will also help to locate the problem!

@Rongzhong Li The switch was in the wrong position I believe but it didn't change anything after I set to arduino. The MPU test code fails also. It will just keep scrolling those numbers forever. Not sure what other photos you are looking for.

Chris

Q: "Sometimes the servos (and thus limbs) just go nuts"

Fully charged 2S battery is 8.4V. The signal that drives servos will be unstable once the batteries' voltage drops below 7.4V, causing the servos to rotate out of control. If Nybble is doing intense motion, like trot, the requirement for voltage is even higher. Dial the resistor clockwisely will lower the requirement for battery voltage, and extends the battery life after one charge. Though the running speed will be correspondingly slower.

The physics here is:

The battery has a limit on power, P=VxI, where P is output power, V is voltage, and I is the current.

Nybble does work through servos. The higher voltage the servo gets, the larger current it will draw from the battery, until the power exceeds the battery's capacity. It will result in a fluctuation in the batteries' voltage, or trigger the batteries' over-current protection.

Q: "After the last of such events it didn't react to anything anymore"

In rare cases the fluctuation in voltage may flip the bits in the onboard or I2C EEPROM, where all the skills are stored as a linked list. If one bit flips, the program won't be able to load the following skills to its memory. But according to your output info (which is quite helpful), it shows the onboard EEPROM is working fine. So it may be the I2C EEPROM. You may fix it by re-uploading the writeInstinct and Nybble. Make sure you are uploading the files downloaded at the same time (i.e. the same version).

Just another possible cause: Did you closed the switch on the battery holder? And have you charged the batteries? The servos requires external power to work.

Yet another note on handling Li-ion batteries: Remember to remove them from the battery holder after use to avoid over discharging. When charging, use the smart charger and keep them in your reach.

The FTDI female socket is supposed to be bent to the other side (belly) if a Pi is mounted. Check the animation on the configuration with Pi. That's why the socket has long legs. I agree that it's still inconvenient to get access to. With a Pi I'm assuming the code on Arduino is pretty done, and most of the commands will be sent through the 2x5 port.

The NyBoard is basically an Arduino Pro Mini with several integrated peripherals. The RXD and TXD in the 2x5 socket are 3.3V, while the FTDI is 5V.

I was going to test using a bluetooth FTDI for uploading sketches and communication, following this tutorial. I should be able to plug it in the FTDI female socket to get rid of the usb cable.

If you get any alternative configuration or customization, please open a post under the other categories of this forum. We'd love to see!

@Rongzhong Li I got the programming working directly from RPi using the GPIO pins. The only addition is another GPIO pin to be used for connecting Pi to DTR. Apart from that a few settings are needed for Arduino IDE setups (namely for avrdude). I'll make another post as soon as I verify the steps with a vanilla RPi Zero W, which is a lot nicer from current consumption perspective than RPi 3B+, which I used as the initial test vehicle.

I would also like to completely get rid of the Desktop environment and use RPi in headless mode. For this I still need to figure out how to compile INO files into HEX files without invoking Arduino IDE. Transferring HEX to Arduino is straightforward from the command line, but I didn't find a way to do the compilation into HEX without the IDE. If someone has the knowledge already then feel free to save me some time on this one!

MemoryFree is a probe for me to test the performance of the code. Maybe I should comment it out in the public version.

Just want to confirm, did you type 'Y' or 'y' in the serial monitor? It's case sensitive. And have you set the "no line ending"?

@Rongzhong Li We do have "no line ending" selected, and I was following WriteInstinct.ino along with the console output and followed the case in the 'if' statement -- which looks to be a 'Y'.

Thanks you for your tip.

What’s the version of your Arduino IDE?

@Rongzhong Li 1.8.9 on both Linux and Mac