CONDENSED UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 02, 2016	Sep. 27, 2015	Oct. 02, 2016	Sep. 27, 2015
Income Statement [Abstract]
Revenue	$ 2,809	$ 4,194	$ 8,476	$ 15,326
Cost of revenue	1,918	2,952	5,653	9,062
Gross profit	891	1,242	2,823	6,264
Operating expenses:
Research and development	2,755	3,684	9,885	10,654
Selling, general and administrative	2,704	2,508	7,988	8,158
Restructuring costs	0	77	0	246
Total operating expenses	5,459	6,269	17,873	19,058
Loss from operations	(4,568)	(5,027)	(15,050)	(12,794)
Interest expense	(37)	(35)	(109)	(64)
Interest income and other expense, net	(41)	(39)	(63)	(98)
Loss before income taxes	(4,646)	(5,101)	(15,222)	(12,956)
(Benefit from) provision for income taxes	(23)	(15)	68	46
Net loss	$ (4,623)	$ (5,086)	$ (15,290)	$ (13,002)
Net loss per share:
Basic (in dollars per share)	$ (0.07)	$ (0.09)	$ (0.24)	$ (0.23)
Diluted (in dollars per share)	$ (0.07)	$ (0.09)	$ (0.24)	$ (0.23)
Weighted average shares:
Basic (in shares)	67,781	56,588	64,522	56,379
Diluted (in shares)	67,781	56,588	64,522	56,379