Product manual

XStream-PKG-R™ RS-232/485 RF Modem – Product Manual v4.2B5

3. RF Modem Operation

3.1. Serial Communications

3.1.1. RS-232 and RS-485/422 Data Flow

Devices that have a UART interface can connect directly through the pins of the XStream Modem

as is shown in the figure below.

Figure 3.1. System Data Flow Diagram in a UART-interfaced environment

(Low-asserted signals distinguished with horizontal line over signal name.)

3.1.2. Host and RF Modem I/O Settings

Serial communications between a host and an XStream RF Modem are dependent upon having

matching baud rate, parity, stop bit and number of data bits settings. Failure to enter the modem

into AT Command Mode is most commonly due to baud rate mismatch. Refer to the table below

to ensure host serial port settings match those of the modem.

Table 3.1. Parameter values critical to serial communications between the RF Modem and host

Parameter Setting

XStream RF Modem Default Parameter Value

Baud (Serial Data Rate)

9600 bps or 19200 baud (Factory-set RF data rates)

Number of Data Bits

8 (NB parameter = 0)

Parity

None (NB parameter = 0)

Number of Stop Bits

1 (NB parameter = 0)

Both the XStream RF Modem and host (PC) settings can be viewed and adjusted using Digi’s

proprietary XCTU Software. Use the “PC Settings” tab to configure host settings. Use the

“Terminal” or “Modem Configuration” tabs to configure the RF Modem settings. Refer to the RF

Modem Configuration sections for more information (p21).