veml6070: add Vishay UV light sensor

veml6070/registers.go

@@ -0,0 +1,65 @@
+package veml6070
+
+// I2C addresses and other constants
+
+const (
+	ADDR_L = 0x38 // 7bit address of the VEML6070 (write, read)
+	ADDR_H = 0x39 // 7bit address of the VEML6070 (read)
+)
+
+// Some possible values for resistance value (in ohm) of VEML6070 calibration resistor
+const (
+	RSET_240K = 240000
+	RSET_270K = 270000
+	RSET_300K = 300000
+	RSET_600K = 600000
+)
+
+// Possible values for integration time of VEML6070
+// (internally represents the config register bit mask)
+const (
+	IT_HALF = 0x00
+	IT_1    = 0x04
+	IT_2    = 0x08
+	IT_4    = 0x0C
+)
+
+// Possible values for UVI (UV index) risk level estimations - the VEML6070 can
+// only estimate UVI risk levels since it can only sense UVA rays but the vendor
+// tried to come up with some coarse thresholds, from application notes
+const (
+	UVI_RISK_LOW = iota
+	UVI_RISK_MODERATE
+	UVI_RISK_HIGH
+	UVI_RISK_VERY_HIGH
+	UVI_RISK_EXTREME
+)
+
+// Scale factor in milliseconds / ohm to determine refresh time
+// (aka sampling time) without IT_FACTOR for any given RSET, from datasheet.
+// Note: 100.0 milliseconds are applicable for RSET=240 kOhm and IT_FACTOR=1
+const RSET_TO_REFRESHTIME_SCALE = 100.0 / RSET_240K
+
+// The refresh time in milliseconds for which NORMALIZED_UVA_SENSITIVITY
+// is applicable to a step count
+const NORMALIZED_REFRESHTIME = 100.0
+
+// The UVA sensitivity in mW/(m*m)/step which is applicable to a step count
+// normalized to the NORMALIZED_REFRESHTIME, from datasheet for RSET=240 kOhm
+// and IT_FACTOR=1
+const NORMALIZED_UVA_SENSITIVITY = 50.0
+
+// Config register
+
+// Possible values for shutdown
+const (
+	CONFIG_SD_DISABLE = 0x00
+	CONFIG_SD_ENABLE  = 0x01
+)
+
+// Enable / disable
+const (
+	CONFIG_DEFAULTS = 0x02
+	CONFIG_ENABLE   = CONFIG_SD_DISABLE | CONFIG_DEFAULTS
+	CONFIG_DISABLE  = CONFIG_SD_ENABLE | CONFIG_DEFAULTS
+)