u-blox LEXI-R422, Руководство по системной интеграции

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LEXI-R422 - System integration manual
UBX-23007449 - R02 System description Page 29 of 108
C1-Public
The configuration and behavior of the UART signals after the boot sequence are described below:
• The module data output line ( RXD ) is set by default to the OFF state (high level) at UART
initialization. The module holds RXD in the OFF state until the module transmits some data.
• The module data input line ( TXD ) is assumed to be controlled by the external host once UART is
initialized. The TXD data input line has an internal active pull-up enabled.
1.9.1.3 UART multiplexer protocol
LEXI-R422 modules include multiplexer functionality as per 3GPP TS 27.010 [8] , on the primary UART
physical link. This is a data link protocol which uses HDLC-like framing and operates between the
module (DCE) and the application processor (DTE) and allows a number of simultaneous sessions over
the primary UART physical link. The following virtual channels are defined:
• Channel 0: for multiplexer control.
•
Channel 1: for all AT commands, and non-Dial Up Network (non-DUN) data connections. UDP,
TCP data socket / data call connections via relevant AT commands.
• Channel 2: for Dial Up Network (DUN) data connection. It requires the host to have and use its
own TCP/IP stack. The DUN can be initiated on modem side or terminal/host side.
• Channel 3: for u-blox GNSS data tunneling.
1.9.2 USB interface
1.9.2.1 USB features
LEXI-R422 modules include a high-speed USB 2.0 interface [4] , available for FW upgrade by means of
the u-blox EasyFlash tool and for diagnostic purposes. The module itself acts as a USB device, and it
can be connected to a USB host such as a Personal Computer equipped with compatible drivers.
LEXI-R422 modules provide the following USB lines:
• the USB_D+ / USB_D- lines, carrying the USB data and signaling
• the USB_5V0 input pin to enable the USB interface by applying an external 5.0 V typical voltage
• the USB_3V3 input pin to supply the USB interface by applying an external 3.3 V typical voltage
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If the USB interface is enabled, the module does not enter the low power deep-sleep mode.
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It is highly recommended to provide accessible test points directly connected to the V_INT ,
PWR_CTRL , USB_5V0 , USB_3V3 , USB_D+ , USB_D- , RSVD #99 pins for FW upgrade and/or for
diagnostic purpose.
1.9.3 I2C interface
LEXI-R422 modules include an I2C-bus compatible interface ( SDA , SCL lines) to communicate with
an external u-blox GNSS receiver and with external I2C devices: the LEXI-R422 module acts as an I2C
host which can communicate with I2C devices in accordance with the I2C bus specifications
[9] .
The SDA and SCL pins have internal pull-up to V_INT , so there is no need of additional pull-up resistors
on the external application board.