Bluetooth Connectivity

The reader should be aware that on occasion it might be difficult to make a successful connection to the Shimmer unit due to the Bluetooth paging mechanism. This is explained below. Paging Inquiry

• The page (and inquiry) window on the RN42 defaults to 320ms (out of a 2.56s). So the RN42 is only “listening” for a connection 12.5% of the time
• When a Bluetooth slave successfully connects or pairs with a BT master they synchronize their frequency hopping pattern. Using a FHS (frequency hopping synchronization) packet if a master has not connected to a slave over a long period of time then the frequency hopping pattern can get severely out of sync (and based on clock drift inside the RN42, this would explain why certain Shimmers seem worse than others). Combine this the 12.5% duty cycle of the page window then it can result in needing multiple attempts to make a connection, but once the connection is made the frequency hopping pattern re-syncs.