weighdemo.py

import sys
import cwiid

def main():
	#Connect to address given on command-line, if present
	print 'Put Wiimote in discoverable mode now (press 1+2)...'
	global wiimote
	if len(sys.argv) > 1:
		wiimote = cwiid.Wiimote(sys.argv[1])
	else:
		wiimote = cwiid.Wiimote()

	wiimote.rpt_mode = cwiid.RPT_BALANCE | cwiid.RPT_BTN
	wiimote.request_status()

#	if wiimote.state['ext_type'] != cwiid.EXT_BALANCE:
#		print 'This program only supports the Wii Balance Board'
#		wiimote.close()
#		return -1

	balance_calibration = wiimote.get_balance_cal()
	named_calibration = { 'right_top': balance_calibration[0],
						  'right_bottom': balance_calibration[1],
						  'left_top': balance_calibration[2],
						  'left_bottom': balance_calibration[3],
						}

	exit = False
	while not exit:
		print "Type q to quit, or anything else to report your weight"
		c = sys.stdin.read(1)
		if c == 'q':
			exit = True
		wiimote.request_status()
		print "%.2fkg" % (calcweight(wiimote.state['balance'], named_calibration) / 100.0, )

	return 0

def calcweight( readings, calibrations ):
	"""
	Determine the weight of the user on the board in hundredths of a kilogram
	"""
	weight = 0
	for sensor in ('right_top', 'right_bottom', 'left_top', 'left_bottom'):
		reading = readings[sensor]
		calibration = calibrations[sensor]

		print(sensor + ' (' + str(reading) +' '+ str(calibration) +')')		
		if reading > calibration[2]:
			print "Warning, %s reading above upper calibration value" % sensor
		# 1700 appears to be the step the calibrations are against.
		# 17kg per sensor is 68kg, 1/2 of the advertised Japanese weight limit.
		if reading < calibration[1]:
			weight += 1700 * (reading - calibration[0]) / (calibration[1] - calibration[0])
		else:
			weight += 1700 * (reading - calibration[1]) / (calibration[2] - calibration[1]) + 1700

	return weight

if __name__ == "__main__":
	sys.exit(main())