| Note 7 - Major Customer Concentration | 6 Months Ended | 
|---|---|
| Mar. 31, 2020 | |
| Notes to Financial Statements | |
| Concentration Risk Disclosure [Text Block] | Note  7.Major Customer Concentration For the  threemonths ended  March 31, 2020, Customer A comprised 21%of the Company’s net sales. For the sixmonths ended  March 31, 2020, Customers A, B and C comprised 20%, 11%and 10%,respectively, of the Company’s net sales. All of these customers were distributors. For the threemonths ended  March 31, 2019, Customers A and B comprised 17%and 10%,respectively, of the Company’s net sales. For the sixmonths ended  March 31, 2019, Customers A and B comprised 18%and 11%,respectively, of the Company’s net sales. These major customers, like our other customers, purchase our products from time to time through purchase orders, and we do nothave any agreements that obligate these major customers to purchase products in the future from us. As of   March 31, 2020,  threecustomers accounted for 12%, 10%and 10%,respectively, or 32%in the aggregate, of accounts receivable. One of these customers is a distributor, oneis a private label original equipment manufacturer and oneis a broadband service provider. As of  September 30, 2019,  twocustomers accounted for 16%,and 12%,respectively, or 28%in the aggregate of accounts receivable. Both of these customers are distributors. |