Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net loss	$ (16,472)	$ (14,542)	$ (18,120)
Adjustments to reconcile net loss to net cash used in operations:
Depreciation	1,120	429	414
Amortization of intangible assets	127	128	132
Impairment of intangible assets	0	0	40
Non-cash share-based compensation expense	1,223	1,007	713
Loss on warrant exchange	0	0	4,967
Inventory write-downs	187	287	42
Other non-cash adjustments	27	(62)	(91)
Change in:
Accounts receivable, net	1,442	(1,018)	(645)
Inventory	(558)	(1,033)	(109)
Other current and non-current assets	(143)	(147)	(155)
Accounts payable	(174)	493	(25)
Accrued liabilities	301	590	335
Deferred revenue	(2,122)	8,271	0
Billings on uncompleted contracts in excess of related costs	168	(230)	(450)
Other long-term liabilities	53	0	0
Net cash used in operating activities	(14,821)	(5,827)	(12,952)
Cash flows from investing activities
Proceeds on sale of property and equipment	4	0	34
Purchases of property and equipment	(895)	(1,140)	(207)
Net cash used in investing activities	(891)	(1,140)	(173)
Cash flows from financing activities
Principal payments under capital leases and long-term debt	(15)	0	(15)
Net proceeds from issuance of common stock and warrants	22,978	6,506	16,114
Net cash provided by financing activities	22,963	6,506	16,099
Net increase (decrease) in cash and cash equivalents	7,251	(461)	2,974
Cash and cash equivalents, at beginning of period	7,888	8,349	5,375
Cash and cash equivalents, at end of period	15,139	7,888	8,349
Supplemental schedule of non-cash investing and financing activities
Non-cash additions to property and equipment	351	165	101
Issuance of common stock for exchange of warrants	0	0	9,869
Issuance of common stock for commitment fee	$ 721	$ 0	$ 0