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5.
Functional specifications
5.1 Description of the Communication Protocol
The protocol aims at connecting one host station with one or various QuickRead units which are
inter-related by a dedicated asynchronous serial line.
The role of these two stations is static and can not be modified: the Personal Computer (host)
will be considered as a master, so as the QuickRead stations will always take the role of slave.
The stations communicate between them through an exchange of ASCII strings having
variable length but ending with ↵, an ASCII control character.
ASCII control character ↵ in any telegram from Host to QuickRead must be carriage
return (<CR>).
ASCII control character ↵ in any telegram from QuickRead to Host can be carriage return
(<CR>) or carriage return + line feed (<CR> + <LF>).
The carriage return (<CR>) is 0D hexadecimal and the line feed (<LF>) is 0A hexadecimal.
Any preliminary phase with respect to the transmission (engagement) or to its conclusion (end)
are not foreseen.
5.2 Commands Addressed to a Single Station
The host transmits a command package, ending with ↵.
The QuickRead answers with an acknowledge package, ending with ↵, just to confirm the
implemented operation required by host, possibly containing the required data.
Host waits for the QuickRead answer before sending any other package.
If the QuickRead station receives a wrong sequence in some parts or signals anomalies through
the communication drivers, it must avoid to answer.
The absence of the QuickRead answer is considered as an error status of the protocol.
The commands addressed to one single station can be identified as:
# , ... , ↵
Selection:
Request:
5.3 Commands Addressed to All Connected Stations ( Broadcast )
The host transmits a command package, ending with ↵.
All the connected QuickRead stations receiving a correct sequence perform the operation
required by host but they do not answer.
The host waits a timeout before sending any other package.
The broadcast commands are 00 , ... ↵ type.
5.4 Network Type
The host can be connected to various QuickRead stations.
The signals that are sent by host are simultaneously received by all the stations (broadcasting),
while only one slave will have to answer at a specific moment.
The host will make use of a selection string addressed to a particular station: therefore, the
stations must have identifiers that do not coincide.
ASCII SERIAL TRANSMISSION PROTOCOL
with
# = 01 , 02 , ... 99 identification.
the commands begin with a non numeric character.
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