Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (7,373)	$ (9,111)	$ (11,267)
Adjustments to reconcile net loss to net cash used in operating activities:
Loss on impairment	0	0	185
Depreciation	326	522	681
Stock-based compensation	616	908	807
Stock-based compensation reversal	0	0	(270)
Provision for doubtful accounts receivable	(5)	(9)	(194)
Provision for slow-moving and obsolete inventories	14	17	(1,400)
Provision for warranties	78	51	196
Amortization of discounts on the Iliad Note	6		0	$ 0
Amortization of loan origination fees	102	4	0
Loss on dispositions of property and equipment	24	2	203
Change in operating assets and liabilities:
Accounts receivable	(131)	1,403	2,240
Inventories	1,876	(2,356)	5,151
Prepaid and other assets	611	(538)	161
Accounts payable	(2,214)	2,047	(1,759)
Accrued and other liabilities	(542)	240	(613)
Deferred revenue	(12)	25	5
Total adjustments	749	2,316	5,393
Net cash used in operating activities	(6,624)	(6,795)	(5,874)
Cash flows from investing activities:
Acquisitions of property and equipment	(132)	(57)	(162)
Proceeds from the sale of property and equipment	3	246	97
Net cash (used in) provided by investing activities	(129)	189	(65)
Cash flows from financing activities:
Proceeds from exercise of stock options and purchases through employee stock purchase plan	0	28	130
Principal payments under finance lease obligations	(3)
Common stock withheld in lieu of income tax withholding on vesting of restricted stock units	(110)	(62)	(49)
Loan origination fees	(208)	0	0
Proceeds from the Iliad Note	1,115	0	0
Proceeds from convertible notes	1,700	0	0
Net (payments on) proceeds from credit line borrowings	(1,400)	2,219	0
Net cash provided by financing activities	1,094	2,185	81
Effect of exchange rate changes on cash	16	(5)	(10)
Net decrease in cash and restricted cash	(5,643)	(4,426)	(5,868)
Cash and restricted cash, beginning of year	6,335	10,761	16,629
Cash and restricted cash, end of year	692	6,335	10,761	16,629
Classification of cash and restricted cash:
Cash					$ 350	$ 6,335	$ 10,761
Restricted cash held in other assets					342	0	0
Cash and restricted cash	692	6,335	10,761	$ 16,629	$ 692	$ 6,335	$ 10,761
Supplemental information:
Cash paid in year for interest	215	4	2
Cash paid in year for income taxes	$ 15	$ 7	$ 14