Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	[1]
Accounts receivable, allowance for doubtful accounts	$ 139	$ 124
Convertible preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	10,591,716	2,171,316
Common stock, shares outstanding (in shares)	10,591,716	2,171,316
Series B Preferred Stock [Member]
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, shares issued (in shares)	38,090	35,819
Convertible preferred stock, shares outstanding (in shares)	38,090	35,819
Series C Preferred Stock [Member]
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, shares issued (in shares)	0	0
Convertible preferred stock, shares outstanding (in shares)	0	0

[1] The condensed consolidated balance sheet as of December 31, 2020 has been derived from the audited consolidated financial statements as of that date.