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Appendix 2
UNIFIED PROTOCOL Epsilon Data Exchange (EDE)
A2.1
General Provisions
This document describes a protocol of data exchange of fuel level sensors «Epsilon»
(hereinafter referred to as FLS) with external devices.
Two types of exchange protocols are supported: in a binary form (HEX) or in a symbolic form
(ASCII-sequences transfer). For work it is recommended to use a binary exchange protocol.
After powering of FLS and before issuing the first command of request you should wait not less
than 250 ms. The command, sent in 250 ms after switching on, will not be accepted by FLS. It is
also possible do not get the answer to the request if the FLS is busy (data processing is
running). In this case, the command should be repeated in 100 ... 200 ms.
The reaction time on the received reading command (except a reading command of supply
voltage) does not exceed 5.5 ms. Reaction time to reading command of supply voltage is
approximately 250 ms. The reaction time to the command of parameters saving is no more than
200 ms. To avoid "hanging" during an unexpected serial interface disconnection timeout on
symbol receiving is used - about 100 ms. If during this time the expected symbol is not received,
FLS does not answer and goes into standby mode to next command.
A2.2
Serial port settings.
Exchange speed corresponds to the parameter set in the sensor (19 200 bit/s by default).
Data capacity - 8 bits.
Parity - not checked.
Stop bit - 1.
Flow control – switched off.
A2.3. Description of commands for binary exchange protocol.
A2.3.1 Message format for binary exchange protocol.
All commands of a binary exchange protocol have the same standardized form:
Commands and messages format for binary exchange protocol.
Field serial number
Name of field
Size of field, Bytes
Description
1
Prefix
1
Field is a marker of message
beginning.
Incoming messages must have
prefix 31h,
and outgoing message must be
issued by a program with prefix
3Eh.
