Integration Manual

LISA-U2 series - System Integration Manual
UBX-13001118 - R25 System description Page 56 of 182
1.9.2.1 UART features
All flow control handshakes are supported by the UART interface and can be set by appropriate AT
commands (see the u-blox AT Commands Manual [2], &K, +IFC, \Q AT commands): hardware flow
control (RTS/CTS), software flow control (XON/XOFF), or none flow control.
☞ Hardware flow control is enabled by default.
One-shot autobauding is supported: the baud rate detection is performed once, at module start-up.
Then the module works at the fixed baud rate (the detected one) and the baud rate can only be
changed via the appropriate AT command (+IPR, for more details, see the u-blox AT Commands
Manual [2]). In particular:
 If automatic baud rate detection is configured in the active memory profile, the baud rate is
detected once at the module power-on
 The factory-programmed setting enables the automatic baud rate detection (<rate> value is 0)
Since autobauding is implemented as “one shot” autobauding, any setting of +IPR=0 should be
avoided; the only exception is if the baud rate is fixed in the stored NVRAM profile. In this case, the
module starts without autobauding and the host needs to reactivate it.
If the system starts in autobauding (i.e. the +IPR is 0), the first “at” sequence provided to the module
detects the baud rate. For example the first command sent from the DTE at any rate can be:
AT+CPIN="1234".Characters different than “AT” are ignored during the baud rate detection since the
“at” or “AT” sequence triggers the hardware detection sequence. “At” or “aT” sequences are invalid:
the two detection characters must be both lowercase or uppercase.
The module generates a response once autobauding detection is successful, the command is
accepted and the command response is available. Therefore, even if the detection was previously
successful, it is only possible to assume that the detection phase was successful after a response.
If the DTE does not receive any response after some time, it must retry (the timeout value should be
adjustable inside the DTE application). In any case, use a very simple command as the first command,
for which the execution time is short and almost constant (e.g. ATE). Note that the only way to recover
from a detection failure is the detection reattempt, since the AT interface is only available after a
successful detection.
☞ One-shot autobauding is enabled by factory programmed setting.
☞ The only way to recover from a detection failure is the detection reattempt, since the AT interface
is only available after a successful detection.
The following baud rates can be configured by AT command:
 1200 bit/s
 2400 bit/s
 4800 bit/s
 9600 bit/s
 19200 bit/s
 38400 bit/s
 57600 bit/s
 115200 bit/s, default value when the one-shot autobauding is disabled
 230400 bit/s
 460800 bit/s
 921600 bit/s
☞ 460800 bit/s and 921600 bit/s baud rates cannot be automatically detected by one-shot
autobauding.