Note 10 - Stockholders' Equity - Stock-based Compensation (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Stock-based compensation	$ 614,000	$ 652,000
Cost of Sales [Member]
Stock-based compensation	3,000	15,000
Selling and Marketing Expense [Member]
Stock-based compensation	185,000	63,000
Research and Development Expense [Member]
Stock-based compensation	98,000	136,000
General and Administrative Expense [Member]
Stock-based compensation	$ 328,000	$ 438,000

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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