Note 11 - Stockholders' Equity (Details Textual) - USD ($)				1 Months Ended	12 Months Ended
	Sep. 22, 2021	Jun. 22, 2020	Jun. 21, 2019	Jul. 21, 2020	Jan. 02, 2022	Jan. 03, 2021	Dec. 29, 2019	Mar. 15, 2019	May 29, 2018
Common Stock, Shares Authorized (in shares)					200,000,000	200,000,000
Preferred Stock, Shares Authorized (in shares)					10,000,000	10,000,000
Payments of Stock Issuance Costs					$ 45,000	$ 1,147,000	$ 1,181,000
Common Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.001	$ 0.001
Proceeds from Issuance of Common Stock					$ 1,342,000	$ 9,296,000	$ 9,437,000
Warrants Issued in Connection with Underwritten Public Offering [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)					$ 19.32
Maximum [Member] | Warrants Issued in Connection with Underwritten Public Offering [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)					386,100
Common Stock [Member]
Stock Issued During Period, Shares, New Issues (in shares)					198,000	2,642,000	1,314,000
Common Stock [Member] | Maximum [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)									386,000
Private Placement [Member]
Payments of Stock Issuance Costs	$ 45,000
Proceeds from Issuance of Common Stock, Net	$ 1.0
Underwritten Public Offering [Member]
Payments of Stock Issuance Costs		$ 1,100,000
Common Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.001
Proceeds from Issuance of Common Stock		$ 8,800,000	$ 8,000,000.0	$ 8,100,000
Shelf Registration Maximum Offering								$ 75,000,000.0
Underwritten Public Offering [Member] | Common Stock [Member]
Stock Issued During Period, Shares, New Issues (in shares)		2,500,000	1,300,000
Common Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.001	$ 0.001
Shares Issued, Price Per Share (in dollars per share)		$ 3.50	$ 7.0
Exercise of Option for Overallotment of Shares by Underwriters [Member]
Payments of Stock Issuance Costs				52,000
Proceeds from Issuance of Common Stock				$ 496,000
Exercise of Option for Overallotment of Shares by Underwriters [Member] | Common Stock [Member]
Stock Issued During Period, Shares, New Issues (in shares)		375,000	171,429	141,733
Underwritten Public Offering, Including Exercise of Overallotment Options by Underwriters [Member]
Payments of Stock Issuance Costs				$ 1,200,000
Proceeds from Issuance of Common Stock, Net				8,100,000
Proceeds from Issuance of Common Stock				$ 9,300,000
Common Stock [Member] | Private Placement [Member]
Stock Issued During Period, Shares, New Issues (in shares)	125,000
Common Stock [Member] | Registered Direct Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares)	73,664