Annual report pursuant to Section 13 and 15(d)

Note 1 - Summary of Significant Accounting Policies (Details Textual)

v3.20.1
Note 1 - Summary of Significant Accounting Policies (Details Textual)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 12, 2019
Mar. 28, 2020
USD ($)
$ / shares
shares
Mar. 30, 2019
USD ($)
$ / shares
shares
Mar. 31, 2018
$ / shares
shares
Mar. 31, 2019
USD ($)
Number of Leases   1      
Operating Lease, Right-of-Use Asset   $ 1,183   $ 1,361
Operating Lease, Liability, Total   1,541      
Research and Development Expense, Total   1,552 1,304    
Asset Impairment Charges, Total   $ 0 $ 0    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares) | shares   73,880 100,267    
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share) | $ / shares   $ 4.98 $ 4.65    
Customer Concentration Risk [Member] | Accounts Receivable [Member]          
Number of Major Customers   3 3    
Concentration Risk, Percentage   96.00% 97.00%    
Equity Incentive Plan 2005 [Member]          
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares) | shares       400,000  
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share) | $ / shares       $ 0.33  
Equity Incentive Plan 2005 [Member] | Share-based Payment Arrangement, Option [Member] | Vesting on the First Anniversary of the Grant Date [Member]          
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage       25.00%  
Equity Incentive Plan 2005 [Member] | Share-based Payment Arrangement, Option [Member] | Vesting Monthly On Each of the 36 Months Following the First Anniversary of the Grant Date [Member]          
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage       2.08%  
Minimum [Member]          
Warranty Term (Year)   1 year      
Minimum [Member] | Machinery and Equipment [Member]          
Property, Plant and Equipment, Useful Life (Year)   3 years      
Maximum [Member]          
Warranty Term (Year)   3 years      
Maximum [Member] | Machinery and Equipment [Member]          
Property, Plant and Equipment, Useful Life (Year)   10 years      
Accounting Standards Update 2016-02 [Member]          
Operating Lease, Right-of-Use Asset         1,361
Operating Lease, Liability, Total         $ 1,800
Reverse Stock Split [Member]          
Stockholders' Equity Note, Stock Split, Conversion Ratio 15