Pololu Robotics & Electronics
Menu
My account Comments or questions? About Pololu Contact Ordering information Distributors

3pi - Remote controlled by BlueTooth!


#1

Hello together,

ever wanted to remote control your 3pi via your BlueTooth enabled notebook? While the hardware is easy to hook up (just attach the RX- and TX signals of bluetooth module to 3pi’s PD0 and PD1 I/Os taking care of the 3,3V <-> 5V issue), the remote control software running at the PC can be really hard to develop. At least it is for me as a very inexperienced PC coder. So I wrote a little Python script that allows the use of the arrow keys for remote controlling the 3pi.

Have fun!

PS: Please excuse the poor formatting of the sourcecode, the board software seems to have it’s own head!

#########################################
# Remote Control Software for 3pi Robot #
# ===================================== #
#										#
# Purpose:								#
# --------								#
# Control 3pi's movements using the		#
# direction keys of a PC's keyboard 	#
#										#
# Prerequisities:						#
# ---------------						#
# - 3pi robot running 3pi-serial-slave  #
#	program example by Pololu			#
# - Python 2.7 and the modules:			#
#   serial, pygame						#
# - RF connection from PC to 3pi's UART #
#   (PD0 and PD1)						#
#				* * *					#
# Tested with Pololus 3pi (Atmega168),	#
# Seeed Studios "Bluetooth Bee",		#
# Sparkfuns "XBee Xplorer Regulated", 	#
# and notebook with built-in BlueTooth 	#
#     ---------------------------       #
#      (C) 2011 Stefan Guenther			#
#        sguenther@elmicro.com			#
#########################################

import pygame, serial, time

#setting the movement parameters
MotorMax 		= 130								#maximum speed
MaxMultiSteer 	= int(round(MotorMax/float(40)))	#maximum nr. of steps for steering
MotorMulti 		= int(round(MotorMax/float(30)))	#multiplier per step of acceleration/deceleration
MotorMultiSteer = int(round(MotorMax/float(12))) 	#maximum nr. of steps for acc/dec

#calculate the maximum nr. of steps for acc/dec
MaxMulti 		= int(round(MotorMax/float(MotorMulti)))
Correction 		= 1.04									#correction factor if motors are uneven

#content: nr. of UP,LEFT,RIGHT,DOWN, states of UP,LEFT,RIGHT,DOWN
Times 			= [0,0,0,0,0,0,0,0]

#Codes for motor movement
Motor1FWD 		= 193
Motor1BWD 		= 194
Motor2FWD 		= 197
Motor2BWD 		= 198

#initialize motor speeds to zero
Motor1Speed 	= 0
Motor2Speed 	= 0

#prepare serial port
port 			= serial.Serial()

#variable that contains the data to be sent to the 3pi
TransmitData	= [Motor1FWD,0,Motor2FWD,0]

#to be developed...
#NothingHappened = 1

#routine for starting the serial connection
def cmdConnect():
	global port
	port.baudrate 	= 115200
	port.port 		= 18
	port.open()

def main():
	global port
	#global NothingHappened
	
	cmdConnect()					#start serial connection
	pygame.init()					#init pygame library
	screen 		= pygame.display.set_mode((200,200)) 
									#"dummy" window needed for key capturing
	app_running = True				#flag used to quit the main loop
	
	global Motor1Speed, Motor2Speed	
	
	while app_running:				#main loop
	
		time.sleep(0.05)			#time pitch for key inputs (in seconds)
		events = pygame.event.get()	#capture mouse and keyboard inputs
		
		for e in events:			#look for interesting events
			
			if e.type == pygame.QUIT:			#"dummy" window has been closed
				app_running = False				#forces exit from main loop on next loop
				break
				
			elif e.type == pygame.KEYDOWN:		#at least one key is pressed
				#NothingHappened = 0		
				if e.key == pygame.K_UP:		#<Up Arrow> is pressed
					Times[4] = 1				#set the corresponding flag
				elif e.key == pygame.K_DOWN:	#(and so on)
					Times[7] = 1
				elif e.key == pygame.K_LEFT:
					Times[5] = 1
				elif e.key == pygame.K_RIGHT:
					Times[6] = 1
				if e.key == pygame.K_ESCAPE:	#<Escape> is pressed
					print "EXITING"				
					app_running = False			
					
			elif e.type == pygame.KEYUP:		#at least one key was released
				#NothingHappened = 0
				if e.key == pygame.K_UP:		#<Up Arrow> was released
					Times[4] = 0				#clears corresponding flag
				elif e.key == pygame.K_DOWN:	#(repeat)
					Times[7] = 0
				elif e.key == pygame.K_LEFT:
					Times[5] = 0
				elif e.key == pygame.K_RIGHT:
					Times[6] = 0
					
			else:								#no change in keyboard state and no key pressed
				Times[4] = 0					#clear all key flags
				Times[5] = 0					#(just for security reason
				Times[6] = 0					# - flags _should_ get cleared if their
				Times[7] = 0					#corresponding key was released)
				#NothingHappened = 1
				
		if Times[4] == 0 and Times[0] > 0:		#if flag for <Up Arrow> is cleared,
			Times[0] -= 1  						#decrement counter for <Up Arrow> if not already zero	
		if Times[5] == 0 and Times[1] > 0:		#(like above)
			Times[1] -= 1
		if Times[6] == 0 and Times[2] > 0:
			Times[2] -= 1
		if Times[7] == 0 and Times[3] > 0:
			Times[3] -= 1
		
		if Times[4] == 1 and Times[0] < MaxMulti:		#flag of <Up Arrow> is set -> counter increment
			Times[0] += 1  								#if not already at maximum
		if Times[5] == 1 and Times[1] < MaxMultiSteer:	#(repeat for each key)
			Times[1] += 1
		if Times[6] == 1 and Times[2] < MaxMultiSteer:
			Times[2] += 1
		if Times[7] == 1 and Times[3] < MaxMulti:
			Times[3] += 1
					
		#calculating the motor speed for linear movement
		Motor1Speed = (Times[0]-Times[3])*MotorMulti
			
		#calculating a temporary variable
		MotorPercentage = Motor1Speed/float(MotorMax)
		
		#calculating the current steering movement
		SteerSpeed = (Times[2]-Times[1])*MotorMultiSteer*MotorPercentage
		
		#limit the accumulated motor speeds so that steering can take effect
		if Motor1Speed+abs(SteerSpeed) >= MotorMax:
			Motor1Speed = MotorMax-abs(SteerSpeed)
		if Motor1Speed-abs(SteerSpeed) <= -MotorMax:
			Motor1Speed = -MotorMax+abs(SteerSpeed)
		
		#linear movement --> both motors running at the same speed
		Motor2Speed = Motor1Speed
		
		#adding the steering speed to the both motors
		Motor1Speed += SteerSpeed
		Motor2Speed += -SteerSpeed		#invert the steering at one motor for more effect
			
		#3pi can't handle negative motor speeds; instead, it uses different
		#control codes for forward/backward movement
		if Motor1Speed < 0:
			TransmitData[0] = Motor1BWD
			#use the Correction value on one motor to equalize both motors
			#float() has to be used if fractal part is necessary for the calulation
			TransmitData[1] = -int(round(Motor1Speed*float(Correction)))				
		else:
			TransmitData[0] = Motor1FWD
			TransmitData[1] = int(round(Motor1Speed*float(Correction)))

		if Motor2Speed < 0:
			TransmitData[2] = Motor2BWD
			TransmitData[3] = -int(round(Motor2Speed))
		else:
			TransmitData[2] = Motor2FWD
			TransmitData[3] = int(round(Motor2Speed))
		
		#Now all values are calculated and can be sent to the 3pi! chr() converts the integer values
		#to single bytes that can be understood by the 3pi
		port.write(chr(TransmitData[0])+chr(TransmitData[1])+chr(TransmitData[2])+chr(TransmitData[3]))

	#these commands are executed after the main loop was left
	pygame.quit()		#close "dummy" windows
	port.close()		#close serial communication
	
if __name__ == '__main__':
	main()

3pi remote control
#2

Hello.

Thanks for sharing your code! A couple of weeks ago, I made a 3pi controlled using 2 Wixels. It was fun to drive it around the office. Do you have any plans for what you will do with it now that it is working?

- Ryan


#3

Hi Ryan,

this is mainly an evaluation project for a bluetooth connection via the BTBee by Seeed Studios (I’m working in a company that sells them). And, of course, just for fun!

As a next step I’ll try to implement some kind of obstacle detection using infrared sensors and/or ultrasonic devices. For these “higher functions”, I think I’ll connect a second controller to the 3pi.

Your Wixels also seems like a nice product - quite similar to the RFBee from Seeed (which uses the 900MHz frequency). The USB port adds even more usability to it. Remarkable is, that the RFBee is based on the Arduino project and can be programmed with the Processing IDE. Besides, after trying to flash the 3pi while it was turned off and the 328p got defective, i desoldered the Atmega168 from one of the RFBees and replaced it with the dead 328p on the 3pi - and it worked! :o)

Best regards,
Stefan.