CONDENSED UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2015	Sep. 28, 2014	Sep. 27, 2015	Sep. 28, 2014
Income Statement [Abstract]
Revenue	$ 4,194	$ 4,124	$ 15,326	$ 22,124
Cost of revenue	2,952	2,361	9,062	13,287
Gross profit	1,242	1,763	6,264	8,837
Operating expenses:
Research and development	3,684	3,057	10,654	8,754
Selling, general and administrative	2,508	2,579	8,158	8,892
Restructuring costs	77	0	246	0
Total operating expenses	6,269	5,636	19,058	17,646
Loss from operations	(5,027)	(3,873)	(12,794)	(8,809)
Interest expense	(35)	(34)	(64)	(67)
Interest income and other expense, net	(39)	(17)	(98)	(79)
Loss before income taxes	(5,101)	(3,924)	(12,956)	(8,955)
Provision for (benefit from) income taxes	(15)	6	46	(18)
Net loss	$ (5,086)	$ (3,930)	$ (13,002)	$ (8,937)
Net loss per share:
Basic (in dollars per share)	$ (0.09)	$ (0.07)	$ (0.23)	$ (0.16)
Diluted (in dollars per share)	$ (0.09)	$ (0.07)	$ (0.23)	$ (0.16)
Weighted average shares: (in shares)
Basic (in shares)	56,588	55,812	56,379	55,208
Diluted (in shares)	56,588	55,812	56,379	55,208