Note 10 - Stock Based Compensation - Compensation Expense (Details) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share-based Payment Arrangement, Expense	$ 280	$ 582	$ 358	$ 1,046
Research and Development Expense [Member]
Share-based Payment Arrangement, Expense	82	184	84	342
General and Administrative Expense [Member]
Share-based Payment Arrangement, Expense	198	368	258	650
Selling and Marketing Expense [Member]
Share-based Payment Arrangement, Expense	$ 0	$ 30	$ 16	$ 54