Note 9 - Summary of Stock Options (Tables)

9 Months Ended

Sep. 30, 2017

Notes Tables

Share-based Compensation, Stock Options, Activity [Table Text Block]

	Nine Months Ended September 30, 2017
						Weighted
				Weighted		Average		Aggregate
	Number			Average		Remaining		Intrinsic
	of			Exercise		Contractual		Value
	Shares			Price		Term (years)		(in thousands)
Options outstanding, beginning of period		1,909,764		$	6.19		9.12	$	211,396
Options granted		739,985		$	5.86
Options exercised		(7,730	)	$	4.02
Options cancelled		(152,040	)	$	9.82
Options outstanding, end of period		2,489,979		$	5.88		8.70	$	387,178
Vested and exercisable and expected to vest, end of period		2,337,350		$	5.88		8.67	$	369,478
Vested and exercisable, end of period		734,721		$	5.90		7.81	$	162,632

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

			Options Outstanding						Options Exercisable
							Weighted
			Number		Weighted		Average		Number		Weighted
			Outstanding		Average		Remaining		Exercisable		Average
Range of			as of		Exercise		Contractual		as of		Exercise
Exercise Prices			September 30, 2017		Price		Term (Years)		September 30, 2017		Price
	$2.64			12,500	$	2.64		7.62		7,553	$	2.64
$3.68	-	$3.76		66,876	$	3.76		7.35		43,191	$	3.76
$4.46	-	$4.92		400,329	$	4.63		8.25		161,941	$	4.77
	$5.22			567,679	$	5.22		9.20		108,555	$	5.22
$5.58	-	$5.67		254,000	$	5.62		9.93		-	$	-
	$6.00			557,753	$	6.00		8.22		244,023	$	6.00
$6.24	-	$6.61		150,639	$	6.44		8.21		45,574	$	6.34
$7.00	-	$7.92		441,825	$	7.65		9.10		85,506	$	7.72
	$9.92			38,135	$	9.92		5.14		38,135	$	9.92
$56.00	-	$296.00		243	$	100.46		3.21		243	$	100.46
				2,489,979	$	5.88		8.70		734,721	$	5.90

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2017		2016		2017		2016
Expected term (in years)	5		5		5		5
Average volatility	64	%	46	%	55	%	54	%
Risk-free interest rate	1.73	%	1.14	%	1.83	%	1.31	%
Dividend yield	0	%	0	%	0	%	0	%

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2017		2016		2017		2016
Cost of revenue	$	5	$	-	$	12	$	-
Research and development		62		31		170		80
Selling, general and administrative		420		241		1,132		582
Total	$	487	$	272	$	1,314	$	662