Log all payload contacts to serial BLE

[adamfowleruk]

[Who] As a wearable developer

[What] I need to log raw RSSI and payload data over Bluetooth Serial to a remote device

[Value] In order to carry out live demonstrations and efficacy testing of my wearables

Describe the potential solution you'd like

A clear and concise description of what you want to happen within Herald.

• Use the Nordic Semi Bluetooth Serial driver and log a csv format of data to it
• Create a new SensorDelegate and use the didMeasure withPayload callback to send data to the bluetooth serial driver
• Prepend this with something like 'SensorDelegate,didMeasureWithPayload,' to allow the same mechanism to be used by other subsystems in future
• Document the format in the API docs for the bluetooth serial adapter
• Ensure this doesn't starve demo apps of available simultaneous connections

Describe alternatives you've considered

A clear and concise description of any alternative solutions or features you've considered.

• Segger RTT - requires DK device (not practical for wearable in-office tests or demos) and a jlink license, and a USB connection

Additional context

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Relative priority

Please give an indication of a relative priority for this enhancement.

HIGH - Used to test physical wearable devices from ourselves plus approx two manufacturers.