UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning balance (shares) at Apr. 30, 2019		11,619,538
Beginning balance at Apr. 30, 2019	$ 2,238	$ 12	$ 72,924	$ (70,698)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	131		131
Net income	(641)			(641)
Ending balance (shares) at Jul. 31, 2019		11,619,538
Ending balance at Jul. 31, 2019	1,728	$ 12	73,055	(71,339)
Beginning balance (shares) at Apr. 30, 2019		11,619,538
Beginning balance at Apr. 30, 2019	2,238	$ 12	72,924	(70,698)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	72
Ending balance (shares) at Jan. 31, 2020		11,823,274
Ending balance at Jan. 31, 2020	3,177	$ 12	73,790	(70,625)
Beginning balance (shares) at Jul. 31, 2019		11,619,538
Beginning balance at Jul. 31, 2019	1,728	$ 12	73,055	(71,339)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	77		77
Issuance of common stock on exercise of stock options (in shares)		625
Issuance of common stock on exercise of stock options and warrants	2		2
Net income	307			307
Ending balance (shares) at Oct. 31, 2019		11,620,163
Ending balance at Oct. 31, 2019	2,114	$ 12	73,134	(71,032)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	229		229
Issuance of common stock on exercise of stock options (in shares)		203,111
Issuance of common stock on exercise of stock options and warrants	427		427
Net income	407			407
Ending balance (shares) at Jan. 31, 2020		11,823,274
Ending balance at Jan. 31, 2020	3,177	$ 12	73,790	(70,625)
Beginning balance (shares) at Apr. 30, 2020		12,726,728
Beginning balance at Apr. 30, 2020	5,318	$ 13	77,978	(72,673)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	120		120
Issuance of common stock on exercise of stock options (in shares)		1,160
Issuance of common stock on exercise of stock options and warrants	0
Net income	75			75
Ending balance (shares) at Jul. 31, 2020		12,727,888
Ending balance at Jul. 31, 2020	5,513	$ 13	78,098	(72,598)
Beginning balance (shares) at Apr. 30, 2020		12,726,728
Beginning balance at Apr. 30, 2020	5,318	$ 13	77,978	(72,673)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	816
Ending balance (shares) at Jan. 31, 2021		13,390,172
Ending balance at Jan. 31, 2021	7,867	$ 13	79,711	(71,857)
Beginning balance (shares) at Jul. 31, 2020		12,727,888
Beginning balance at Jul. 31, 2020	5,513	$ 13	78,098	(72,598)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	85		85
Issuance of common stock on exercise of stock options (in shares)		640,657
Issuance of common stock on exercise of stock options and warrants	1,294		1,294
Net income	1			1
Ending balance (shares) at Oct. 31, 2020		13,368,545
Ending balance at Oct. 31, 2020	6,893	$ 13	79,477	(72,597)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	232		232
Issuance of common stock on exercise of stock options (in shares)		21,627
Issuance of common stock on exercise of stock options and warrants	2		2
Net income	740			740
Ending balance (shares) at Jan. 31, 2021		13,390,172
Ending balance at Jan. 31, 2021	$ 7,867	$ 13	$ 79,711	$ (71,857)