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E2E Bluetooth 4.0 Compliant Sensor v1.0

Overview

The E2E sensor (E2ES) is a Bluetooth 4.0-compliant device that logs temperature data. E2ES

was designed to be easy to use and to overcome the shortfalls of other similar devices.

E2ES uses a virtual UART-style communication scheme on top of Bluetooth 4.0 services. E2ES

logs data in a circular fashion and may make use of its single push-button and green LED

for user interaction. E2ES also has provisions for additional sensors such as Light or Vibration.

Bluetooth Attributes

E2ES design is based on the Nordic nRF52832 ARM based device with integrated 2.4 GHz

radio which exhibits the following characteristics:

- Advertise Interval

- Battery Life

1 - 2 Seconds

~3 Years

Logger Attributes

E2ES logging is built on top of the Nordic platform but is an abstraction that can be adapted to

other radio communication devices. Many of the properties of the logging facilities are

governed by the underlying platform and may change in future updates or diﬀerent hardware.

Logging is mildly conﬁgurable. All conﬁgurable options can be set over Bluetooth while the

logger is Stopped.

- Data Point Limit

- Data Storage Method

- Temperature Range

- Temperature Accuracy

- Log Interval

- Log Delay

12,000

32 bit word with 3 10-bit temperatures and 2 bits for mark data

-50 to +50 Degrees Celsius

+/- 0.5 Degrees Celsius

1 to 2^16 Seconds

E2ES Interaction

E2ES Interaction begins with a Bluetooth 4.0 scan. All valid E2ES are Generally Discoverable

and will advertise a packet containing the name ‘E2ESensor’ in the payload. Once found, issue

a Service Discovery to ﬁnd the transmit and receive services. Communication is now possible

by writing data to the transmit channel and reading from the receive channel.

E2ESensor

Bluetooth

Central

RX Char: 00000002-0043-4C4C-5049-5254706D6554

TX Char: 00000003-0043-4C4C-5049-5254706D6554

E2ES communication can be done in two ways. The ﬁrst way is to do a ‘write verify’ on the TX

line. A write verify will only return once the RX buﬀer has been ﬁlled and you can safely do a

read from the RX channel. The second way would be to write data on the TX channel and await

a ‘notify’ event that indicated the RX channel has data available. The ﬁrst method is well tested

and the current recommended approach.

Summary of content (7 pages)

PAGE 1
E2E Bluetooth 4.0 Compliant Sensor v1.0 Overview The E2E sensor (E2ES) is a Bluetooth 4.0-compliant device that logs temperature data. E2ES was designed to be easy to use and to overcome the shortfalls of other similar devices. E2ES uses a virtual UART-style communication scheme on top of Bluetooth 4.0 services. E2ES logs data in a circular fashion and may make use of its single push-button and green LED for user interaction. E2ES also has provisions for additional sensors such as Light or Vibration.
PAGE 2
© 2018 End2End Sensors LLC, ALL RIGHTS RESERVED E2ES States E2ES may be in one of three states: Idle Started Silenced In the Idle state, no data is being logged and there is no radio activity. The only way to remove the E2ES from Idle is to manually push the button. In the Started state, data is being logged in the circular buﬀer and the Radio is functioning. The only way to stop the E2ES from logging is to issue the Halt command.
PAGE 3
© 2018 End2End Sensors LLC, ALL RIGHTS RESERVED Discovering Endian of Central system (Example in javascript): function checkEndian() { if (endianness === undefined) { var a = new ArrayBuﬀer(4); var c = new Uint32Array(a); c[0] = 0x01020304; if(b[0] === 0x04) return 0; // Little if(b[0] === 0x01) return 1; // Big } } Command List Info Command Takes no arguments and returns a known response format containing all available information about the connected E2ES.
PAGE 4
© 2018 End2End Sensors LLC, ALL RIGHTS RESERVED Read Block Command Takes a single uint8 type argument designating the Block to read. Returns a data payload equal in bytes to the ‘Data Bytes per Block’ value returned by the Info command. Ex: TX -> 0x01 0x52 Args… - Endian - Command (Read) - uint8 value for the sequential block number to read. RX <0x52 0x00 0x04 - Command (Read) - Error (success) - Block Number (4) Unlock Command Takes a 16 byte argument that must be the calculated challenge response.
PAGE 5
Quell Command Takes two uint16 type arguments. The first argument represents the Logging Interval in seconds and the second represents the Log Delay in seconds. If the Log Interval is not supplied (0x0000) The E2ES will use its internal default value of 600 seconds. Log Delay functionality is optional and accepts a value of 0. Quelling the E2ES causes all data to be cleared and starts device logging with an optionally new Log Interval.
PAGE 6
© 2018 End2End Sensors LLC, ALL RIGHTS RESERVED E2ES Common Operation The general use case for E2ES is to find it, read some or all of the data available, and then optionally Quell it and/or silence it. If going into storage, Halting is also an option. Since the data storage method and block size may change with future firmware or new hardware it is best to write code that is dynamic based on information from the Info command.
PAGE 7
Known Issues Planned Future Changes - All Arguments that have values in time (seconds) will be increased to 32 bit types. - Security Challenge will be calculated and enforced. - Info command will return seconds since last data point was logged for increased time accuracy. - Data will be stored in non-volatile memory so it is not lost on error. - Light Sensor will be added with similar functionality to the button Mark.