lora: add starting point for US915 settings

Signed-off-by: deadprogram <ron@hybridgroup.com>

lora/config.go

@@ -80,6 +80,7 @@ const (
 const (
 	MHz_868_1 = 868100000
 	MHz_868_5 = 868500000
+	MHz_902_3 = 902300000
 	MHz_916_8 = 916800000
 	MHz_923_3 = 923300000
 )

lora/lorawan/region/us915.go

@@ -0,0 +1,51 @@
+package region
+
+import "tinygo.org/x/drivers/lora"
+
+const (
+	US915_DEFAULT_PREAMBLE_LEN = 8
+	US915_DEFAULT_TX_POWER_DBM = 20
+)
+
+type RegionSettingsUS915 struct {
+	joinRequestChannel *Channel
+	joinAcceptChannel  *Channel
+	uplinkChannel      *Channel
+}
+
+// see https://www.thethingsnetwork.org/docs/lorawan/regional-parameters/#us902-928-ism-band
+
+func US915() *RegionSettingsUS915 {
+	return &RegionSettingsUS915{
+		joinRequestChannel: &Channel{lora.MHz_902_3,
+			lora.Bandwidth_125_0,
+			lora.SpreadingFactor10,
+			lora.CodingRate4_5,
+			US915_DEFAULT_PREAMBLE_LEN,
+			US915_DEFAULT_TX_POWER_DBM},
+		joinAcceptChannel: &Channel{lora.MHz_923_3,
+			lora.Bandwidth_500_0,
+			lora.SpreadingFactor7,
+			lora.CodingRate4_5,
+			US915_DEFAULT_PREAMBLE_LEN,
+			US915_DEFAULT_TX_POWER_DBM},
+		uplinkChannel: &Channel{lora.MHz_902_3,
+			lora.Bandwidth_125_0,
+			lora.SpreadingFactor7,
+			lora.CodingRate4_5,
+			US915_DEFAULT_PREAMBLE_LEN,
+			US915_DEFAULT_TX_POWER_DBM},
+	}
+}
+
+func (r *RegionSettingsUS915) JoinRequestChannel() *Channel {
+	return r.joinRequestChannel
+}
+
+func (r *RegionSettingsUS915) JoinAcceptChannel() *Channel {
+	return r.joinAcceptChannel
+}
+
+func (r *RegionSettingsUS915) UplinkChannel() *Channel {
+	return r.uplinkChannel
+}