Bots-hitechnic-compass

Back to Robotics Main Page

---

HiTechnic compass

• Detailed design and usage information for the HiTechnic compass sensor
• Because of the way the registers are mapped you can use the UltrasonicSensor class to work with this compass. The value returned by get_sample()is 1/2 the actual heading in degrees, that is you multiply the returned value by 2 to calculate the heading.
• Calibration is rarely necessary and shouldn't be an issue for us in the near-term.
• Example code:

#!/usr/bin/env python
# This example uses the "plain" UltraSonic (i.e. digital) sensor interface 
# with the HiTechnic compass sensor.  The compass_heading() function 
# attempts to do the conversion to degrees (but omits the adder register 
# as documented by HiTechnic).  

import time
import nxt.locator
from nxt.sensor import *

def id_nxt(b):
	name, host, signal_strength, user_flash = b.get_device_info()
	print 'NXT brick name: %s' % name
	print 'Host address: %s' % host
	print 'Bluetooth signal strength: %s' % signal_strength
	print 'Free user flash: %s' % user_flash
              
def compass_heading(b, p):
	# Because of limitations in the UltraSonic interface it returns 1/2 the 
	# actual heading.
	return UltrasonicSensor(b, p).get_sample() * 2

print 'Looking for brick 1 ...'
sock = nxt.locator.find_one_brick(host='00:16:53:06:ED:B8', name='NXT')

if sock:
	print 'Found brick 1' 
else:
	print 'Timed-out, no NXT bricks found, exiting' 
	exit

if sock:
	print 'Connecting to the brick ...'
	bot = sock.connect()
 	
	if bot:
		print 'Connected to the brick'
	else:
		print 'Timed-out connecting to brick 1, exiting'
		exit

	if bot:
		id_nxt(bot)

		while 1:
			print 'Compass heading: ', compass_heading(bot, PORT_4) 
			time.sleep(1)