Motion Tracking on the Cheap with a PIC


motion tracking

Ever need a cheap motion tracker for very basic object following? Did you know you can throw one together with a few IR distance sensors and a PIC?

The setup is fairly simple. [Aron Horan] is using a dsPIC30F4011 PIC, a SHARP infrared distance sensor, an RC servo, and a PICkit2 for testing. It works by scanning left and right using the servo motor. When the edge of an object is detected, it will turn away from the object until it can no longer detect the edge — then it turns back. Unfortunately this does mean it will always be twitching, even when it’s tracking an object.

Like many of the other projects [Aron] has documented, he’s included everything you need to know to be able to recreate the project yourself. Flowcharts, wiring diagrams, and the code — written in C of course! The following video includes an excellent demonstration, but…

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Bluetooth Controlled Car

In this project I plan to control a robot via bluetooth using a serial bluetooth module the hc-05.
I firstly wanted to get familiar with changing the state of the robot with a hard wired serial to USB device. I built a simple circuit with three LED’s and code that has three different states; one state for each LED to be turned on, then a python script to send different characters via a USB to serial port.

Here is a circuit diagram of the system:


Here is a picture of the circuit:



Here is my code:

// Testing serial control with USB serial to dsPIC30F4011
// Written by Aron Horan
// 10 Dec 2013
#include <xc.h>
#include <libpic30.h>
// Configuration settings
_FOSC(CSW_FSCM_OFF & FRC_PLL16); // Fosc=16x7.5MHz, i.e. 30 MIPS
_FWDT(WDT_OFF);                  // Watchdog timer off
_FBORPOR(MCLR_DIS);              // Disable reset pin

int main(void)
	int state = 0;
    char g, h, j, c; 
    TRISB = 0;
    // Configure UART
	U1BRG = 48;            // 38400 baud @ 30 MIPS
	U1MODEbits.UARTEN = 1; // Enable UART

		// Check if any characters were received via UART
        if (U1STAbits.URXDA == 1)     
            // Check that first character was 'f,g or h'
            c = U1RXREG;
            if (c == 'g') state = 1;
            else if (c == 'h') state = 2;
            else if (c == 'j') state = 3;

		//LED on RD0
		if (state == 1) 
			LATB = 0b001;
		//LED on RD1
		if (state == 2)
			LATB = 0b010;
		//LED on RD2
		if (state == 3)
			LATB = 0b100;
	return 0;

I firstly wanted to setup the python to send a char every three seconds, after I get that going I will change it so that it will take inputs from my keyboard.
I also am using a USB to serial port for the moment, once I get that up and running I will setup the bluetooth serial port and control remotely.

Here is my python code that sends a different char every three seconds:

import time
import serial

# configure the serial connections
ser = serial.Serial(
while True:

	print "g"
	print "h"
	print "j"

Here is a video of it in action:

Now that I have that working I have edited the python script to recieve inputs from the keyboard to change state.

Here is the new python code:

import time
import serial

# configure the serial connections (the parameters differs on the device you are connecting to)
ser = serial.Serial(
while True:

#print 'Enter your commands below.\r\nInsert "exit" to leave the application.'
	# get keyboard input
	input = raw_input(">> ")
        # Python 3 users
        # input = input(">> ")
	if input == 'exit':
		# send the character to the device
		# (note that I happend a \r\n carriage return and line feed to the 			characters - this is requested by my device)
		ser.write(input + '\r\n')
		out = ''
		# wait half a second before reading output (give device time 			 	     # to answer)
		while ser.inWaiting() > 0:
			out +=
		if out != '':
			print ">>" + out

The only thing is the I must press enter (return) for the char to be sent. My next stage I will overcome this problem. Also instead of using the USB to serial port I will be using a serial Bluetooth device so I can transmit wirelessly.

So I finally got it working.

Its wirelessly switching a few LEDs (wow!) but now I have the power to do a lot more with it.

I ended up using Tkinter to create a canvas with 3 buttons. Each button sends a different character to the PIC, changing it between three different states.

My C programm is exactly the same as above the only difference is the python script.

Here is my Python script:

import time
import serial
import Tkinter
# Define a keyboard callback function. This will be called
# every time a key is pressed anywhere in the window.
def key(event):
    print "Sending", repr(event.char)
# Callback function for the 'A' button
def a_press():
    print "Sending 'g'"
# Callback function for the 'B' button
def b_press():
    print "Sending 'h'"
# Callback function for the 'C' button
def c_press():
    print "Sending 'j'"
# Open first serial port
ser = serial.Serial(port='/dev/rfcomm0', baudrate = 9600, timeout=1)
# Create a Tk GUI window
root = Tkinter.Tk()

# create canvas with a width and height
Tkinter.Canvas(root, width=600, height=600)

# Add title to window
# Bind all keypresses to the "key" function (define above)
root.bind("<Key>", key)
# Create a few buttons and connect each one to a function
a = Tkinter.Button(root, text='A', command=a_press)
b = Tkinter.Button(root, text='B', command=b_press)
c = Tkinter.Button(root, text='C', command=c_press)
# Lay out buttons in the GUI
a.grid(row=0, column=0, sticky='EW')
b.grid(row=1, column=0, sticky='EW')
c.grid(row=2, column=0, sticky='EW')
root.columnconfigure(0, weight=1)
# Enter the Tkinter main event loop. The program will stay
# in this event loop until it's time to exit.
# Close serial port

Here is a video of it in action:

Having awful trouble with my bluetooth device, possible blew it somehow 😦 gonna order a new one and will get back to this project when it arrives.