MicroPython Air Boat

My daughter’s and I have built a number of air boat projects, but this time I thought that I’d try it using MicroPython. MicroPython is a lean and efficient implementation of the Python 3 programming language that includes a small subset of the Python standard library and is optimised to run on microcontrollers.

For this project my goal was to create a MicroPython application that was a standalone WiFi access point, and its used a small web server for controlling the air boat fans.

Hardware

The hardware that I used on this project included:

• 1 – ESP8266 module ($5-$10)
• 2 – L9110 Fans ($5 each)
• 1 – Uno proto shield (optional) or use a small breadboard
• 9V battery or portable phone charger
• K-Nex blocks
• small plastic box
• 2 – plastic water bottles
• duct tape

MicroPython is supported on a number of Wifi enabled ESP32 and ESP8266 modules. These modules are well priced with the NodeMCU modules starting around $5. It’s important to note that most of the ESP-8266 modules also support Lua and Arduino C/C++ programming.

nodemcu

For this project I used an Wemos ESP-8266 module, that comes in a Arduino Uno form factor. I like the Wemos modules because I can used my Uno proto shields and these modules supports 5V DC, as opposed to the typical MicroPython modules that only support 3.3V. The fans will work with 3.3V but they generate a lot more wind power at 5V.

The L9110 fans are designed for Arduino projects and they only cost about $5. These fans have four pins: VCC, GND, INA (direction), and INB (on/off). For this project I only used forward spinning fans, so only pin INB was used.

L9110_fan

Boat Construction

For the boat frame I used K’Nex pieces because they are light weight and sturdy, however there a lot of other materials that could be used. Water bottles were used for flotation, and duct tape was used to secure the bottles to the frame. To help protect the electronics a small plastic snack container was used. I wire wrapped the fans to the boat frame.

airboat

MicroPython Setup

There are a few choices for MicroPython development. I found that the uPyCraft IDE offered a nice integrated environment (Figure 5), and there are some excellent tutorials to help you get started.

upycraft

For MicroPython projects you typically create 2 Python applications, a boot.py and a main.py file. I like to equate this to Arduino where you have a setup() function and a loop() function. For this example I wanted to keep the documentation simple so I put everything in the boot.py file, but it’s recommended to use main.py for larger projects.

Creating an Access Point

The picture below shows how to setup an access point in just a few lines of code. For this example the access point is called ‘ESP32’ with a password of ‘12345678’. When the code is run you will be able to see when a remote user connects and disconnects to the access point.

access_point

MicroPython Web Server

After getting the Access Point working the next step is to create a Web server. This is a simple Web server project so I embedded the HTML content into my Python code, however for a more complex application I would definitely have my web pages as files that are independent from the code.

For the Web Server example application , we start with the access point connection code, then we setup a socket on port 80. The HTTP request/response sequence is passed through a function called web_page(request). In web_page(request) the code looks for keywords in the HREF request.

# MicroPython boot.py - Access Point Web Server

try:
  import usocket as socket
except:
  import socket

import network

station = network.WLAN(network.AP_IF)
station.active(True)
station.config(essid='ESP32')
station.config(authmode=3,password='12345678')

while station.isconnected() == False:
  pass

print('Connection successful')
print(station.ifconfig())

def web_page(request):
  
  fans_state = ""
  if request.find('/?forward') > 0:
    fans_state="Going Forward"
  if request.find('/?Stopped') > 0:
    fans_state="Stopped" 
  
  html = """<html><head> <title>Ice Boat Web Server</title> 
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="icon" href="data:,"> <style>
  html{font-family: Helvetica; display:inline-block; margin: 0px auto; text-align: center;}
  h1{color: #0F3376; padding: 2vh;}p{font-size: 1.5rem;}
  .button{display: inline-block; background-color: #e7bd3b; border: none; 
  border-radius: 4px; color: white; text-decoration: none; font-size: 30px; width:100%}
  </style></head>
  <body> <h1>Ice Boat Web Server</h1> 
  <p>ICE Boat : <strong>""" + fans_state + """</strong></p>
  <p><a href='/?forward'><button class="button">Forward</button></a></p>
  <p><a href='/?stop'><button class="button button">STOP</button></a></p>
  
  </body></html>"""
  
  return html

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(('', 80))
s.listen(5)

while True:
  conn, addr = s.accept()
  print('Got a connection from %s' % str(addr))
  request = conn.recv(1024)
  request = str(request)
  print('The Content = %s' % request)
  response = web_page(request)
  conn.send(response)
  conn.close()

The embedded HTML code passes keywords using anchor tags, for example: <a href=’/?forward’>. Often we use mobile frameworks like Bootstrap to help with formatting, however because we’re running a standalone access point we need to manually define all our style codes.

To access our MicroPython web server, use the address: 192.168.4.1. This is the default address (in the access point setup you can change this). When our web server is running we should be able to toggle the stop/forward states.

screen2

Writing Outputs

The MicroPython command line interface is good way to test outputs. To access the command line interface, use the connect button and then enter “Control-C”.

To manage pins on the hardware, machine library is used :

from machine import Pin

Then pin objects can be defined as either inputs or outputs:

Pin14 = Pin(14, Pin.IN)
Pin5 = Pin(5, Pin.OUT)

The value of a pin is read using: pinobject.value(), and set with: pinobject.value(thevalue) .

motor_test

Final Application

Now that we have all the pieces working independently we can pull it all together. For the final code I’ve defined two fans (motorR and motorL), and a fan control function is called from the web requests.

# MicroPython boot.py - Access Point and Airboat Web Controls
import time
try:
  import usocket as socket
except:
  import socket

from machine import Pin
import network

# Define the left, right and back fans pin
motorR = Pin(12,Pin.OUT)
motorL = Pin(4,Pin.OUT)

# start with fans stopped, Note: my FANs are 0=run
motorR.value(1)
motorL.value(1)


station = network.WLAN(network.AP_IF)
station.active(True)
station.config(essid='ESP32')
station.config(authmode=3,password='12345678')

while station.isconnected() == False:
  pass

print('Connection successful')
print(station.ifconfig())

def fancontrol(left,right):
  motorL.value(left)
  motorR.value(right)

def web_page(request):
  
  fans_state = "Stopped"
  if request.find('/?forward') > 0:
    fans_state="Going Forward"
    fancontrol(0,0)
  if request.find('/?left') > 0:
    fans_state="Going Left"
    fancontrol(1,0)
  if request.find('/?right') > 0:
    fans_state="Going Right" 
    fancontrol(0,1)
  if request.find('/?stop') > 0:
    fans_state="Stopped"
    fancontrol(1,1)
  
  html = """<html><head> <title>Air Boat Web Server</title> 
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="icon" href="data:,"> <style>
  html{font-family: Helvetica; display:inline-block; margin: 0px auto; text-align: center;}
  h1{color: #0F3376; padding: 2vh;}p{font-size: 1.5rem;}
  .button{display: inline-block; background-color: #e7bd3b; border: none; 
  border-radius: 4px; color: white; text-decoration: none; font-size: 30px; width:100%}
  .button2{background-color: #4286f4; width:49%}
  </style></head>
  <body> <h1>Air Boat Web Server</h1> 
  <p>Air Boat : <strong>""" + fans_state + """</strong></p>
  <p><a href='/?forward'><button class="button">Forward</button></a></p>
  <p><a href='/?left'><button class="button button2">LEFT</button></a>
  <a href='/?right'><button class="button button2" >RIGHT</button></a></p>
  <p><a href='/?stop'><button class="button button">STOP</button></a></p>
  
  </body></html>"""
  
  return html

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(('', 80))
s.listen(5)

while True:
  conn, addr = s.accept()
  print('Got a connection from %s' % str(addr))
  request = conn.recv(1024)
  request = str(request)
  print('The Content = %s' % request)
  response = web_page(request)
  conn.send(response)
  conn.close()

airboat_moving

Summary

You’ll be quite surprised about how fast even 2 fans will move the air boat. Balancing the direction of the fans or adding a simple rudder may be required to ensure that it keeps a straight forward direction.

I’ve done the same project on the exact same hardware in Anduino C++ and I would say the response speed is similar but the Python code might be slightly leaner. I found that the MicroPython IDE wasn’t as robust as the Arduino IDE, but I really enjoyed doing interactive Python testing from a command prompt.

I won’t be giving up on Arduino C++, but I can definitely see a place for MicroPython, especially for projects with lots of string manipulation.

 

PSP Controlled Arduino Airboat

We thought that it would be fun to try and use an old PlayStation Portable (PSP) on some Arduino and Pi Projects. If you don’t a have PSP you can usually find a used one at a good price.

Some smart people were able to modify or “mod” the PSP firmware so that it is possible to run open source applications on the PSP. We tried using Python, Lua, sdlBasic and SSH to talk between our PSP  and our Arduinos and Pi’s, but none of these methods were simple or 100% reliable. In the end we found that basic built-in PSP Web browser worked the best and it didn’t require a ‘moded’ PSP.

airboat

PSP Setup and Limitations

We were using an older PSP-1000 so if you have a newer PSP GO or PSP Vita you may not have the same limitation that we found. However we think if you stick to our ‘worst case’ setup you should be good to go.

Our recommended setup was:

  • Simple Web Pages
  • No Browser Cache
  • Simple Wireless Network

For the PSP-1000 the web pages had to be very simple, no CSS (Cascading Style Sheets) and no advanced HTML tagging. We had hoped to show Node-Red Web pages from the PI but this was not possible.

In our testing we found that it was important to turn off the browser cache, otherwise we found that our commands would only work once. To turn off the PSP browser cache, go into the PSP browser and select “Tools”, then “Settings”, and “Cache Settings”.

cache

Our older PSP-1000 had some problems with the newer WPA2 wireless encryption, so to simplify things we created a small standalone open network. For Arduino projects this isn’t a problem because the Arduino can be made into a standalone access point. On Pi projects where you are using an existing wireless network you might need to do some tweeking to add a guest account.

To add a new connection on the PSP go to the “Network Settings” and select “Infrastructure Mode”. Then select “[New Connection]” and “Scan”. The scan will only show networks that the PSP is able to connect to.

networksettings

A Simple Web Form

An HTML form supports two types of action, a POST and a GET. The GET method is the simpler (but less secure) approach and it passes parameters on the URL command line.

Below is a simple Web form:

<html>
<body>
<h1>Click a button to control the car</h1>
<form action='GO' method='GET' >
<INPUT TYPE='submit' VALUE="GO" >
</form>
<form action='STOP' method='GET' >
<INPUT TYPE="submit" VALUE="STOP" >
</form>
<form action='LEFT' method='GET' >
<INPUT TYPE='submit' VALUE="LEFT" >
</form>
<form action='RIGHT' method='GET' >
<INPUT TYPE="submit" VALUE="RIGHT" >
</form>

</body>
</html>

menu

An Arduino Web Server

To create Arduino WiFi projects the ESP8266 based modules are low cost way to go. There are some good ESP8266 libraries and the examples are fairly easy to follow. The ESP8266 module can be wired into an Arduino Uno/Nano/Mega module or you can by buy boards with the ESP8266 chip integrated in. For our testing we used an older WeMo board, but other options like the NodeMCU, Adafruit HUZZAH or even the Arduino Yún could be used.

The ESP8266WebServer library has a simple standalone access point example. We modified this example (WifiAccessPoint) to include HTML form tags for all our required action.

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>

int pinleft = 12;
int pinright = 13;
int pinfront = 14;

/* Set these to your desired credentials. */
const char *ssid = "MY8266";
const char *password = "";

char *webpage = "<html><head><title>My8266 Control</title> \
</head><body> \
<h1>Click a button to control the car</h1>

<hr>

\
<form action='/go' method='GET' > \
<input type='submit' style='font-size:150px;color:lime' value='GO'></form>

\
<form action='/stop' method='GET'> \
<input type='submit' style='font-size:150px;color:red' value='STOP'></form>

 \
<form action='/left' method='GET'> \
<input type='submit' style='font-size:150px' value='LEFT'></form>

 \
<form action='/right' method='GET'> \
<input type='submit' style='font-size:150px' value='RIGHT'></form>

 \
</body></html>";

ESP8266WebServer server(80);

/* Just a little test message. Go to http://192.168.4.1 in a web browser
* connected to this access point to see it.
*/
void handleRoot() {
Serial.println("Base page");
server.send(200, "text/html", webpage);
}

void go() {
Serial.println("Go forward");
server.send(200, "text/html", webpage);
digitalWrite(pinleft,LOW);
digitalWrite(pinright,LOW);
digitalWrite(pinfront,LOW);

}
void stop() {
Serial.println("Stop");
server.send(200, "text/html", webpage);
digitalWrite(pinleft,HIGH);
digitalWrite(pinright,HIGH);
digitalWrite(pinfront,HIGH);
}
void left() {
Serial.println("Go left");
server.send(200, "text/html", webpage);
digitalWrite(pinleft,HIGH);
digitalWrite(pinright,LOW);
digitalWrite(pinfront,HIGH);

}
void right() {
Serial.println("Go right");
server.send(200, "text/html", webpage);
digitalWrite(pinleft,LOW);
digitalWrite(pinright,HIGH);
digitalWrite(pinfront,HIGH);
}

void setup() {
delay(1000);
Serial.begin(115200);
Serial.println();
pinMode(pinleft,OUTPUT);
pinMode(pinright,OUTPUT);
pinMode(pinfront,OUTPUT);

digitalWrite(pinleft,HIGH);
digitalWrite(pinright,HIGH);
digitalWrite(pinfront,HIGH);

Serial.print("Configuring access point...");
/* You can remove the password parameter if you want the AP to be open. */
WiFi.softAP(ssid, password);

IPAddress myIP = WiFi.softAPIP();
Serial.print("AP IP address: ");
Serial.println(myIP);
server.on("/", handleRoot);
server.on("/go",go);
server.on("/stop",stop);
server.on("/left",left);
server.on("/right",right);
server.begin();
Serial.println("HTTP server started");
}

void loop() {
server.handleClient();
}