Only use the low bit of the extended channels packet for arm status

Author: CapnBry

src/lib/CrsfProtocol/crsf_protocol.h

@@ -198,6 +198,11 @@ typedef struct crsf_channels_s
     unsigned ch15 : 11;
 } PACKED crsf_channels_t;
 
+/**
+ * Bits used in the byte following crsf_channels_t in the ExpressLRS extended CHANNELS_PACKED packet
+ */
+#define CRSF_CHANNELS_STATUS_FLAG_ARM (1 << 0)
+
 typedef struct deviceInformationPacket_s
 {
     uint32_t serialNo;

src/lib/tx-crsf/TXModuleEndpoint.cpp

@@ -122,7 +122,9 @@ void TXModuleEndpoint::RcPacketToChannelsData(const crsf_header_t *message) // d
     // frame len 24 -> arming mode CH5: use channel 5 value
     // frame len 25 -> arming mode Switch: use commanded arming status in extra byte
     //
-    armCmd = message->frame_size == 24 ? CRSF_to_BIT(localChannelData[4]) : payload[readByteIndex];
+    armCmd = message->frame_size == CRSF_FRAME_SIZE(sizeof(crsf_channels_t))
+        ? CRSF_to_BIT(localChannelData[AUX1])
+        : (payload[readByteIndex] & CRSF_CHANNELS_STATUS_FLAG_ARM);
 
     // monitoring arming state
     if (lastArmCmd != armCmd)