Note 4 - Stock-based Compensation - Summary of Stock Option Activity (Details) - Employee Stock Purchase Plan ESPP [Member] - $ / shares	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Balance (in shares)	70,515	77,285	63,915
Balance, Weighted Average Exercise Price (in dollars per share)
Options granted (in shares)	55,227	63,607	55,766
Options granted, Weighted Average Exercise Price (in dollars per share)	$ 5.45	$ 6.35	$ 7.88
Shares Available for Grant, Options Granted (in shares)	(55,227)	(63,607)	(55,766)
Options exercised (in shares)	(11,981)	(17,561)	(10,893)
Options exercised, Weighted Average Exercise Price (in dollars per share)	$ 5.72	$ 6.69	$ 8.34
Options canceled (in shares)	(26,628)	(52,816)	(31,503)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	26,628	52,816	31,503
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	55,227	63,607	55,766
Balance (in shares)	87,133	70,515	77,285
Balance , Weighted Average Exercise Price (in dollars per share)
Shares Available For Grant [Member]
Shares Available for Grant (in shares)	450,007	365,581	389,844
Options granted (in shares)	55,227	63,607	55,766
Shares Available for Grant, Options Granted (in shares)	(55,227)	(63,607)	(55,766)
Options canceled (in shares)	(18,087)	(13,614)	(31,503)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	18,087	13,614	31,503
Shares Available for Grant, Plan Expired (in shares)		(365,581)
Shares Available for Grant, Plan Authorized (in shares)		500,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	55,227	63,607	55,766
Shares Available for Grant (in shares)	412,867	450,007	365,581