Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Balance at Jan. 01, 2012	$ 24,938	$ 39	$ 190,025	$ 113	$ (165,239)
Balance (in shares) at Jan. 01, 2012		38,636,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under stock plans and employee stock purchase plans, shares		748,000
Common stock issued under stock plans and employee stock purchase plans	1,148	1	1,147
Private stock Offering, net of issuance costs and warrants, shares		5,122,000
Private stock offering, net of issuance costs and warrants	9,345	5	9,340
Issuance of common stock from exercise of warrants	2,236		2,236
Change in unrealized gain on available-for-sale securities (See Note 4)	(124)			(124)
Stock-based compensation	2,049		2,049
Net loss	(12,314)				(12,314)
Balance at Dec. 30, 2012	27,278	45	204,797	(11)	(177,553)
Balance (in shares) at Dec. 30, 2012		44,506,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under stock plans and employee stock purchase plans, shares		542,000
Common stock issued under stock plans and employee stock purchase plans	966	1	965
Private stock Offering, net of issuance costs and warrants, shares		8,740,000
Private stock offering, net of issuance costs and warrants	23,126	8	23,118
Change in unrealized gain on available-for-sale securities (See Note 4)	11			11
Stock-based compensation	1,493		1,493
Net loss	(12,276)				(12,276)
Balance at Dec. 29, 2013	40,598	54	230,373	0	(189,829)
Balance (in shares) at Dec. 29, 2013		53,788,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under stock plans and employee stock purchase plans, shares		2,358,000
Common stock issued under stock plans and employee stock purchase plans	4,702	2	4,700
Private stock offering, net of issuance costs and warrants	40		40
Issuance of common stock warrants (in shares)		36,000
Issuance of common stock from exercise of warrants	0	0	0
Stock-based compensation	3,306		3,306
Net loss	(13,079)				(13,079)
Balance at Dec. 28, 2014	$ 35,567	$ 56	$ 238,419	$ 0	$ (202,908)
Balance (in shares) at Dec. 28, 2014		56,182,000