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13
Users Guide
XE1401SK Hardware
5.2.7
XE1401SK Host Controller Interface ports - RS232 / USB
5.2.7.1 RS232
PORT
The XE1401SK has one 9-way D-type connector wired as a modem type serial port. The XE1401 UART signals
are routed via the RS232 level shifter MAX3225E (U11) to the on board RS232 connector J4. The MAX3225E goes
into power down mode when no RS232 cable is present.
RS232 port - pin assignment
JP11 allows disconnection of the XE1401 UART signals UA_RX and UA_CTS from the RS232 level shifter -
MAX3225E. The XE1401 UART can be directly accessed through JP2 (50 pins connector for external application
boards).
Note!
It is important that the enclosed “straight” cable (pin1-pin1, pin2-pin2, etc.) is used when connecting to the
serial port of a PC. A null modem cable (RX/TX crossed) will not work!
5.2.7.2 USB
PORT
The XE1401SK has an USB series B (slave) port. If the USB cable is connected, signals from the UART interface
of the XE1401 are routed to the USB controller which converts data to USB data and vice versa. The USB
controller is a Cypress AN2135SC. It has an integrated 8051 CPU. The on-chip memory is loaded with firmware at
power up from the external, serial I
2
C memory.
Since the USB connector on the PC also provides power, no external power supply is needed if jumper JP13 is set
into position “USB_5V”. The UART signals from the Bluetooth™ baseband controller XE1401 are automatically
converted by the firmware running on the USB controller.
Note!
When the XE1401 UART is interfaced through a user specific external application board, the USB port
should be deactivated by removing the USB cable (connected on J2).
