Condensed Statement of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities
Net loss	$ (11,589)	$ (14,274)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,297	1,069
Loss on disposal of property and equipment	20	19
Stock-based compensation	2,397	2,064
Non-cash interest expense	219	286
Compensation expense related to vesting of common stock to GLOBALFOUNDRIES		709
Changes in operating assets and liabilities:
Accounts receivable	1,954	(1,876)
Inventory	779	309
Prepaid expenses and other current assets	466	154
Right-of-use assets	23
Accounts payable	518	(140)
Accrued liabilities	(1,444)	4,840
Operating lease liabilities	(72)
Shipping term reversal		(39)
Net cash used in operating activities	(5,455)	(6,879)
Cash flows from investing activities
Purchases of property and equipment	(566)	(1,513)
Net cash used in investing activities	(566)	(1,513)
Cash flows from financing activities
Proceeds from the issuance of common stock, net of offering costs		24,524
Proceeds from debt		1,000
Payments on debt	(4,840)	(1,000)
Payments of debt issuance costs	(80)
Payments on finance lease obligation	(8)	(8)
Proceeds from exercise of stock options and purchase of shares in employee stock purchase plan	178	2,364
Proceeds from issuance of common stock in at-the-market offering, net of issuance costs	2,172
Net cash (used in) provided by financing activities	(2,578)	26,880
Net (decrease) increase in cash and cash equivalents	(8,599)	18,488
Cash and cash equivalents at beginning of period	23,379	12,950
Cash and cash equivalents at end of period	14,780	31,438
Supplementary cash flow information:
Interest paid	373	370
Operating cash flows paid for operating leases	1,264
Financing cash flows paid for finance leases	8
Right-of-use assets obtained in exchange for new operating leases	23
Non-cash investing and financing activities:
Purchases of property and equipment in accounts payable	33	183
Modification of warrant	$ 36
Issuance of warrant with debt		$ 43