Note 3 - Income Taxes - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Stock compensation expense	$ 173	$ 1,240
Goodwill	591	986
Royalty accruals	10	560
Bad debt allowance	51	338
Net operating loss carryforwards	11,950	10,959
Credit carry-forwards	992	841
Inventory reserve	217	206
Depreciation	556	499
Other	376	334
Total deferred tax assets	14,916	15,963
Deferred tax liabilities:
Intangible assets	(105)	(126)
Total deferred tax liabilities	(105)	(126)
Net deferred tax asset before valuation allowance	14,811	15,837
Valuation allowances for deferred tax assets	(14,950)	(15,971)	$ (15,394)
Net deferred tax liability	$ (139)	$ (134)