Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net loss	$ (12,457)	$ (11,951)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Stock-based compensation	2,938	4,065
Depreciation and amortization	1,922	1,893
Amortization of acquired intangible assets	576	748
Deferred income tax expense (benefit)	(22)	4
Reversal of uncertain tax positions	(2)	(10)
Accretion on short-term marketable securities	0	(10)
Gain on sale of marketable securities	0	(4)
Changes in operating assets and liabilities:
Accounts receivable, net	(1,679)	4,990
Inventories	868	634
Prepaid expenses and other current and long-term assets, net	497	1,343
Accounts payable	1,418	191
Accrued current and long-term liabilities	(2,295)	(1,804)
Income taxes payable	189	77
Net cash provided by (used in) operating activities	(8,047)	166
Cash flows from investing activities:
Purchases of property and equipment	(393)	(612)
Proceeds from sales and maturities of short-term marketable securities	250	7,498
Purchases of short-term marketable securities	0	(1,500)
Net cash provided by (used in) investing activities	(143)	5,386
Cash flows from financing activities:
Proceeds from issuance of common stock under employee equity incentive plans	1,063	337
Payments on asset financings	(506)	(328)
Proceeds from line of credit	0	4,329
Net proceeds from "at the market" equity offering	0	2,474
Proceeds from Paycheck Protection Program loan	0	796
Net cash provided by financing activities	557	7,608
Net increase (decrease) in cash and cash equivalents	(7,633)	13,160
Cash and cash equivalents, beginning of period	31,257	7,257
Cash and cash equivalents, end of period	23,624	20,417
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds received	177	211
Cash paid during the period for interest	69	107
Non-cash investing and financing activities:
Acquisitions of property and equipment and other assets under extended payment terms	$ 0	$ 1,392