Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accounts receivable, allowance for doubtful accounts	$ 37	$ 66
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)	10,640,537	10,619,846
Common stock, shares outstanding (in shares)	10,640,537	10,619,846
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)	41,767	40,504
Convertible preferred stock, shares outstanding (in shares)	41,767	40,504
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