UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue	$ 2,158	$ 3,510	$ 7,439	$ 9,396
Cost of revenue	1,117	1,767	3,397	4,734
Gross profit	1,041	1,743	4,042	4,662
Operating expenses:
Research and development	3,139	2,461	9,596	7,526
Selling, general and administrative	2,095	2,509	6,881	7,680
Total operating expenses	5,234	4,970	16,477	15,206
Loss from operations	(4,193)	(3,227)	(12,435)	(10,544)
Interest expense	(63)	(21)	(270)	(77)
Interest income and other (expense), net	55	17	153	26
Loss before income taxes	(4,201)	(3,231)	(12,552)	(10,595)
Provision for (benefit from) income taxes	70	29	(171)	119
Net loss	$ (4,271)	$ (3,260)	$ (12,381)	$ (10,714)
Net loss per share:
Basic and diluted	$ (0.04)	$ (0.03)	$ (0.12)	$ (0.12)
Weighted average shares outstanding:
Basic and diluted	116,387	94,725	104,173	87,040