Ewave BaseWAVE, Technical Manual

Page: 11 / 20

Ewave Radio Modem User’s Manual V1.02
Copyright © 2001 by Ewave, Inc. 11
Configuration
Name Description Packet Size
Threshold
(bytes)? Wait before
Transmittal
(millisec.)? CRC
? Retry
? Typical Use
“Fast” Maximum Data
Throughput with
Minimum
Latency 1 0 OFF OFF
“Checksum” High Reliability set by user set by user ON user
“Break” High Reliability
with RS232
“Break” and
RTS/CTS
Signalling set by user set by user ON ON Remote
Debugging &
Remote Download
of Parallax Basic
Stamps
“RM2000” Fixed-Length
Packets with CRC
but no Retries 26 (fixed
size) complete
packet OFF OFF Robot Control &
Telemetry
3.8 Command state vs. Data state
Normally the Ewave Radio Modem is in the Data state, in which all bytes sent to the modem via its serial
port are treated as user data and transmitted.
Depending on the configuration of the Ewave Radio Modem, it may also be possible to place the modem in
Command state. In this state, bytes sent to the modem via its serial port are interpreted as commands,
allowing on-the-fly reconfiguration of some or all modem settings and saving of modified settings in
EEPROM. The settings, which may be changed, depend on the protocol configuration of the Ewave Radio
Modem. The default factory Baud Rate is set to 9600 N81.
Whenever the modem enters Command state, or whenever the modem processes a valid Command, it sends
a response of “OK” followed by a <CR><LF>. While in command state, Radio Data reception is disabled.
Invalid commands result in a response of “ER”<CR><LF>.
Depending on the type of Radio Modem, different commands are available to the end user.
Exactly how or if Command state can be accessed depends on the modem’s protocol configuration and the
setting of the Attention flag. If the Attention flag is OFF, then regardless of protocol configuration the
modem can only enter Command state immediately after power is applied. The modem must be powered-
up with RTS asserted, and then RTS must be toggled five times with less then 10 seconds between toggles.
See diagram below:
10 Seconds Max
RTS
Power On Command State
If any bytes are received on the modem’s serial port during this toggling sequence, the modem will
immediately enter Data state (the received byte will be lost). To re-enter Command state, the modem must
once again be power cycled, with RTS asserted and the toggling sequence repeated.