Note 2 - Summary of Significant Accounting Policies - Stock Options Vested and Expected to Vest (Details)	12 Months Ended
	Sep. 28, 2019 $ / shares shares
Number of shares (in shares) | shares	231,337
Weighted-average remaining contractual life (Year)	3 years 361 days
Weighted average exercise price (in dollars per share)	$ 8
Exercisable number of shares (in shares) | shares	171,937
Exercisable weighted- average exercise price (in dollars per share)	$ 9.39
Range One [Member]
Range of exercise prices, lower (in dollars per share)	2.01
Range of exercise prices, upper (in dollars per share)	$ 3
Number of shares (in shares) | shares	20,300
Weighted-average remaining contractual life (Year)	6 years 324 days
Weighted average exercise price (in dollars per share)	$ 2.69
Exercisable number of shares (in shares) | shares	9,800
Exercisable weighted- average exercise price (in dollars per share)	$ 2.73
Range Two [Member]
Range of exercise prices, lower (in dollars per share)	3.01
Range of exercise prices, upper (in dollars per share)	$ 4
Number of shares (in shares) | shares	46,500
Weighted-average remaining contractual life (Year)	9 years 193 days
Weighted average exercise price (in dollars per share)	$ 3.61
Exercisable number of shares (in shares) | shares	8,400
Exercisable weighted- average exercise price (in dollars per share)	$ 3.64
Range Three [Member]
Range of exercise prices, lower (in dollars per share)	4.01
Range of exercise prices, upper (in dollars per share)	$ 5
Number of shares (in shares) | shares	16,600
Weighted-average remaining contractual life (Year)	4 years 270 days
Weighted average exercise price (in dollars per share)	$ 4.34
Exercisable number of shares (in shares) | shares	14,200
Exercisable weighted- average exercise price (in dollars per share)	$ 4.37
Range Four [Member]
Range of exercise prices, lower (in dollars per share)	5.01
Range of exercise prices, upper (in dollars per share)	$ 10
Number of shares (in shares) | shares	37,000
Weighted-average remaining contractual life (Year)	4 years 73 days
Weighted average exercise price (in dollars per share)	$ 7.75
Exercisable number of shares (in shares) | shares	28,600
Exercisable weighted- average exercise price (in dollars per share)	$ 7.90
Range Five [Member]
Range of exercise prices, lower (in dollars per share)	10.01
Range of exercise prices, upper (in dollars per share)	$ 15
Number of shares (in shares) | shares	110,937
Weighted-average remaining contractual life (Year)	350 days
Weighted average exercise price (in dollars per share)	$ 11.44
Exercisable number of shares (in shares) | shares	110,937
Exercisable weighted- average exercise price (in dollars per share)	$ 11.44