CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (5,688)	$ (11,612)	$ (8,383)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	3,502	3,343	787
Depreciation and amortization	1,384	987	1,453
Amortization of intangible assets	1,222	1,235	1,236
Amortization of debt discount	82	646	504
Deferred income taxes	(1)	1	(26)
Gain from settlement with former foundry supplier		(1,962)
Changes in fair value of preferred stock warrant liability			907
Changes in assets and liabilities:
Accounts receivable	(2,557)	425	(4,542)
Inventories	(632)	2,186	85
Prepaid expenses and other current assets	(478)	1,761	(1,004)
Other non-current assets	(270)	(1)
Accounts payable	2,521	(3,584)	1,866
Accrued compensation and benefits	1,015	706	(42)
Accrued expenses and other current liabilities	58	711	32
Other non-current liabilities	75
Deferred rent	(422)	300
Net cash used in operating activities	(189)	(4,858)	(7,127)
Cash flows from investing activities:
Acquisition of property and equipment	(2,868)	(2,481)	(559)
Acquisition of intangible assets	(350)
Issuance of note receivable	(334)	(181)
Net cash used in investing activities	(3,552)	(2,662)	(559)
Cash flows from financing activities:
Proceeds from public offering, net of underwriting discounts and commissions	18,363		22,101
Proceeds from exercise of stock options and employee stock purchase plan	781	239	10
Tax withholdings related to net share settlement of restricted stock units	(308)
Proceeds from revolving line of credit	30,598	7,415
Payments on revolving line of credit	(30,905)	(5,608)	(4,273)
Proceeds from term loan, net of fees	12,000	17,825	14,903
Payments on term loan	(16,364)	(15,650)	(7,600)
Net cash provided by financing activities	14,165	4,221	25,141
Effect of exchange rates on cash and equivalents	(65)	(71)	(338)
Net increase (decrease) in cash and cash equivalents	10,359	(3,370)	17,117
Cash and cash equivalents - beginning of period	19,719	23,089	5,972
Cash and cash equivalents - end of period	30,078	19,719	23,089
Supplemental disclosures of other cash flow information:
Cash paid for interest expense	695	688	521
Supplemental disclosures of non-cash investing and financing information:
Purchase of property and equipment included in accounts payable	420	$ 1,033
Conversion of note receivable into investment in preferred shares of unconsolidated affiliate	363
Accrued deferred financing costs	$ 125
Issuance of preferred stock warrants in connection with term loan Conversion of convertible preferred stock to common stock			863
Conversion of convertible preferred stock to common stock			78,467
Reclassification of warrant liability to additional paid-in-capital upon closing of initial public offering			$ 1,892