User's Manual

MaxStream, Inc. 24XStream Wireless Module Manual v2.8
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Glossary
AT commands – A set of commands that
can be used to customize and configure the
24XStream module to meet specific needs.
AT commands are sent via a serial
communications program such as
HyperTerminal.
Binary commands – Another set of
commands used to configure the 24XStream
module. Binary commands are sent with
RTS/CMD asserted. The RT command
must be used to enable binary programming
prior to using binary commands. Multiple
Binary commands can be issued sequentially
while RTS/CMD is asserted.
Clear to send – See “CTS pin”.
CMOS logic – Logic levels used by the
24XStream module. (0-5V)
Command Mode – A mode of operation
wherein the configurable parameters of the
24XStream module can be manually
adjusted. Both Binary and AT command
modes are available.
Command table – Table containing all 23
currently implemented commands. This
table lists all of the adjustable parameters
along with a brief description of each.
CRC – See “Cyclic redundancy check”.
CTS pin – The low-asserted Clear To Send
pin (Pin 1) provides flow control for the
24XStream module. When CTS is asserted
(low), serial data can be sent to the module
for transmission. If the module is unable to
transmit the data, CTS may de-assert (high)
once the data buffer nears capacity to
prevent buffer overflow.
Cyclic redundancy check (CRC) – Used
by the 24XStream module to ensure data
integrity during transmission. A CRC is
computed on the bits to be transmitted over-
the-air and sent with each data packet. The
CRC is recomputed by the receiver and
compared with the original CRC bits. The
packet is valid if the receiver CRC matches
the CRC computed by the transmitter.
Cyclic sleep – Sleep Mode setting in which
the module enters a low-power state and
awakens periodically to determine if any
transmissions are being sent.
Data buffer – Collects incoming serial data
prior to over-the-air data transmission. The
data buffer can hold up to 132 bytes at a
given time. When the buffer fills to 115
bytes, the Clear To Send (CTS) pin is de-
asserted to stop the flow of incoming serial
data.
Data packets – A grouping of data to be
sent over-the-air. Each data packet contains
a header and data that is collected from the
data buffer. The size of the packets varies up
to 64 bytes depending on how many bytes of
data are in the data buffer.
Data validity – Comparing received data
with transmitted data to ensure accurate
transmission. Data validity is verified by
performing a CRC check.
DI pin – All incoming serial data enters the
24XStream module on the Data In pin (Pin
4).
DO pin – All received over-the-air data
leaves the 24XStream module through the
Data Out pin (Pin 3) and can then be sent to
a microcontroller or RS-232 device.
FCC – The Federal Communications
Commission (FCC) is the US government
agency responsible for regulating radio
communications standards in the US.
Flow control – Method of determining
when serial data can be sent to the module
for over-the-air transmission. Flow control
is used to prevent buffer overflow. This can
be implemented in hardware and/or
software. Hardware flow control is
implemented in the 24XStream module
using the *CTS pin.
Frequency Hopping Spread Spectrum
(FHSS) – Method employed by the
24XStream module which involves
transmitting data over several different
channels in a specific channel hopping
sequence known by the transmitter and the
receiver(s).