Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net loss	$ (14,669)	$ (17,754)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,694	1,450
Loss on disposal of property and equipment	20	19
Stock-based compensation	3,554	2,668
Non-cash gain on warrant revaluation	(3)
Non-cash interest expense	290	375
Compensation expense related to vesting of common stock to GLOBALFOUNDRIES		753
Changes in operating assets and liabilities:
Accounts receivable	1,723	(3,816)
Inventory	1,234	694
Prepaid expenses and other current assets	149	(98)
Accounts payable	202	(178)
Accrued liabilities	(2,210)	1,253
Operating lease liabilities	(100)
Shipping term reversal		(39)
Net cash used in operating activities	(8,116)	(14,673)
Cash flows from investing activities
Purchases of property and equipment	(861)	(1,914)
Net cash used in investing activities	(861)	(1,914)
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	(11)	(11)
Proceeds from exercise of stock options and purchase of shares in employee stock purchase plan	282	2,503
Proceeds from issuance of common stock in at-the-market offering, net of issuance costs	4,734
Net cash provided by financing activities	85	27,016
Net (decrease) increase in cash and cash equivalents	(8,892)	10,429
Cash and cash equivalents at beginning of period	23,379	12,950
Cash and cash equivalents at end of period	14,487	23,379
Supplementary cash flow information:
Interest paid	480	504
Cash paid for taxes	48	30
Operating cash flows paid for operating leases	1,693
Financing cash flows paid for finance leases	11
Non-cash investing and financing activities:
Right-of-use assets obtained in exchange for new operating leases	23
Increase of right-of-use asset and lease liability due to lease modification	895
Purchase of property and equipment in accounts payable and accrued liabilities	57	11
Modification of warrant	$ 36
Issuance of warrant with debt		$ 43