Note 1 - The Company and Basis of Presentation (Details Textual)										1 Months Ended		12 Months Ended
		Dec. 11, 2020	Jun. 22, 2020 USD ($) $ / shares shares	Dec. 06, 2019	Nov. 26, 2019	Nov. 25, 2019	Nov. 06, 2019 USD ($)	Jun. 21, 2019 USD ($) $ / shares shares	Dec. 21, 2018 USD ($)	Jul. 21, 2020 USD ($) shares	May 31, 2018 $ / shares shares	Jan. 03, 2021 USD ($) $ / shares shares	Dec. 29, 2019 USD ($) $ / shares shares	Dec. 30, 2018 USD ($) shares	Sep. 28, 2019 USD ($)	Dec. 20, 2018 USD ($)	Sep. 28, 2018 USD ($)
Restructuring Costs, Total												$ 753,000	$ 0	$ 0
Cash and Cash Equivalents, at Carrying Value, Ending Balance												22,748,000	21,548,000
Line of Credit, Current												$ 15,000,000	$ 15,000,000
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares												$ 0.001	$ 0.001
Proceeds from Issuance of Common Stock												$ 9,296,000	$ 9,437,000	$ 16,215,000
Reverse Stock Split Ratio, Authorized					15	5
Reverse Stock Split [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio				14
Underwritten Public Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares) | shares											965,251
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares			$ 0.001								$ 0.001
Common Stock [Member]
Stock Issued During Period, Shares, New Issues (in shares) | shares	[1]											2,642,000	1,314,000	965,000
Common Stock [Member] | Underwritten Public Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares) | shares			2,500,000					1,300,000
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares			$ 0.001					$ 0.001
Shares Issued, Price Per Share (in dollars per share) | $ / shares			$ 3.50					$ 7.00
Proceeds from Issuance of Common Stock			$ 8,800,000					$ 8,000,000.0		$ 8,100,000
Common Stock [Member] | Exercise of Option for Overallotment of Shares by Underwriters [Member]
Stock Issued During Period, Shares, New Issues (in shares) | shares			375,000					171,429		141,733
Proceeds from Issuance of Common Stock										$ 496,000
Heritage Bank of Commerce [Member] | Revolving Credit Facility [Member]
Cash and Cash Equivalents, at Carrying Value, Ending Balance												$ 22,600,000
Line of Credit, Current												$ 15,000,000.0	$ 15,000,000.0
Line of Credit Facility, Maximum Borrowing Capacity									$ 15,000,000.0						$ 9,000,000.0	$ 9,000,000.0	$ 9,000,000.0
Minimum Cash Required for Covenant Related to Credit Facility							$ 3,000,000.0		$ 3,000,000.0
Line of Credit Facility, Expiration Period (Year)		1 year					1 year		1 year
Debt Instrument, Interest Rate, Stated Percentage							5.50%
Debt Instrument, Interest Rate, Effective Percentage												3.75%	5.50%
Heritage Bank of Commerce [Member] | Revolving Credit Facility [Member] | Prime Rate [Member]
Debt Instrument, Basis Spread on Variable Rate		0.50%					0.50%

[1] Common stock, par value and additional paid-in capital amounts are adjusted to reflect 1-for-14 reverse stock split effected on December 23, 2019.