Command Line

Published on 2016-04-10 in Tote HaD.

The robots are built, but due to a bug in the communication code, they didn’t walk “straight out of the box”. The bug makes them wait for a connection before they start walking, and I will be fixing this soon, and I will provide new firmware to flash soon.

In the mean time, you can play with your robots by using a serial connection. In fact, you will have access to the Python console on them. All you need is a 3.3V USB2TTL converter (I gave out a couple at the workshop, it’s that red thing with USB plug on it). If you don’t have one, I highly recommend you get it anyways, because they are extremely useful in debugging all sorts of projects anyways, and you will also need to to flash the new firmware, both for the Arduino and the ESP8266 parts of the robot.

Connecting

To connect the serial interface of the ESP8266 on your robot to your computer, you will need to use the three pins on the left side of the robots. If you look at the bottom side of the board, you will see they are labeled, from front to back, “gnd”, “tx” and “rx”. Use three female-female dupont cables, and connect the “gnd” pin on the robot with the “gnd” pin on the USB2TTL, the “rx” pin of the robot with the “tx” pin on the USB2TTL, and the “tx” pin on the robot with the “rx” pin on the USB2TTL.

  • gnd ↔ gnd

  • rx ↔ tx

  • tx ↔ rx

Next, plug the USB2TTL into your computer (or even better, a USB hub connected to your computer), and open a serial terminal with speed 115200 on the serial port that appears. On Linux, I use the_screen_ program for that, with the command:

$ screen /dev/ttyUSB0 115200

On Windows you can use PuTTY for that (you might need to have the drivers for the USB2TTL installed first). I have no idea how to do that on macs, but there must be some way. Once you do that, you should see black screen… Then switch on the robot, and you should see something like this:

rll��|�l�|�l�b|����r�b�b��nn�lnn���bplblrlp�n��lbn�|쌌��b��nn�l��l`�nnl`nr���nr�`p�n�r�����bn�|lb��nn�l`�nnl`nr���nrrl`p�n�r�����쌜bn�|쌎b��nn�l`�nnl`nr���nl`r��nl`�l��|��rrnb��l��b�lb쌜���l��b�lrldon't use rtc mem data
ll��|��rrnb��ll�p�b�b쌜���l��b��lrl�l��|��rrnb��ll�|�b�b쌜����b�lblrl��rl���bl�br|�bll���lb��n�nn��l�|�l�l��l������l`�n��

That’s the booting messages of the ESP8266 received at a wrong baud rate. Don’t worry about that. Now, if you press Ctrl+C, the program that is executing on the robot will be interrupted, and you will see this:

MicroPython v1.6-374-g2c407bc-dirty on 2016-04-07; ESP module with ESP8266
Type "help()" for more information.
>>>

That’s the Python console prompt, also known as the REPL console. You can type Python code in there, and it will get executed on the robot.

Walking

So how do you make it walk? Type in this code:

from robot import Robot
from gait import Creep
robot = Robot()
gait = Creep(robot)
for frame in gait.run():
    pass

That should get the robot creeping forward. To change the directions you can set the_dx_,dy and_rotation_ attributes on the_gait_ object, and repeat the_for_ loop.

Network

By default the robot will create its own network, and act as an access point – that’s because I didn’t know what networks will be available at the conference, and of course I wanted the robots to still work after you have taken them home. Unfortunately, when I tested the code, I did it with the robot connected to my home network, for convenience. That’s how the bug crept in – I didn’t test it in the access point mode, just assumed it would work the same way.

But that means that you should be able to work around the bug by connecting the robot to your home network. Here is how to do it. First, disable the “access point” interface:

import network
network.WLAN(network.AP_IF).active(False)

Then enable the “station” interface:

wlan = network.WLAN(network.STA_IF)
wlan.active(True)

And then make it connect to your network:

wlan.connect("ssid", "password")

The robot will remember this, and will re-connect to that network automatically on every boot from now on.

Remote Control

The robot has very simple remote control through WiFi for now. Once you restart it, you should be able to connect to it on port 1010 with Telnet or Netcat, and send it “wasd” letters for arrows, and space for “stop”. Depending on the program you use, you might need to press enter after each of the letters. To simplify that, there is a client.py program in the repository, which uses PyGame to read the arrow keypresses, and sends them to the robot. You run it with the IP address of the robot as the first argument.

Moving Individual Legs

There isn’t much other functionality implemented yet, but if you want, you can make the robot move its legs however you want from Python, and even make it dance or do something else… You can do it using the “robot” object above. For instance, to make the front left leg move 20mm forward and 10mm up, you would do:

robot.legs[0].move_to(0, 20, -10)
robot.update()

The “update” step is where the command is actually sent to the servos. The coordinate system for the legs is simple: X axis is left-right, with negative numbers being closer to the body, and positive numbers further from it. The Y axis is front-back, with positive numbers being forward, and negative – backward. The Z axis is up-down, with positive being down, and negative – up. The (0, 0, 0) position is the robot’s starting position, with all servos centered.

Updates

I will definitely fix the bug, and maybe even figure a better way to control the robot remotely. When I do, the new firmware and instructions for flashing it will be available here on this project page. I will also make updates as the amazing developers of Micropython add more features to it. At the moment they are working on a web-based interactive Python console, including file upload, which should make hacking on this robot super-convenient. However, this is all still in the alpha stage of development at the moment, so we will have to make do with what we have now.