LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
System description
Page 63 of 125
1.9.5
MUX Protocol (3GPP 27.010)
LISA-U1 series modules have a software layer with MUX functionality,
3GPP TS 27.010 Multiplexer Protocol
available either on the UART or on the SPI physical link. The USB interface doesn’t support the multiplexer
protocol.
This is a data link protocol (layer 2 of OSI model) 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 used
physical link (UART or SPI): the user can concurrently use AT command interface on one MUX channel and
Packet-Switched / Circuit-Switched Data communication on another MUX channel. The multiplexer protocol can
be used on one serial interface (UART or SPI) at a time. Each session consists of a stream of bytes transferring
various kinds of data such as SMS, CBS, PSD, GPS, AT commands in general. This permits, for example, SMS to
be transferred to the DTE when a data connection is in progress.
The following virtual channels are defined:
Channel 0: control channel
Channel 1 – 5: AT commands /data connection
Channel 6: GPS tunneling
For more details please refer to
GSM Mux implementation Application Note
1.10
DDC (I
2
C) interface
1.10.1
Overview
An I
2
C compatible Display Data Channel (DDC) interface for communication with u-blox GPS receivers is available
on LISA-U1 series modules. This interface is dedicated exclusively to access u-blox GPS receivers.
Name
Description
Remarks
SCL
I
2
C bus clock line
Open drain. External pull-up required.
SDA
I
2
C bus data line
Open drain. External pull-up required.
Table 24: DDC pins
The DDC (I
2
C) interface pins ESD sensitivity rating is 1 kV (HBM according to JESD22-A114F). Higher
protection level could be required if the lines are externally accessible on the application board. Higher
protection level can be achieved by mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor
array) on the lines connected to these pins.
u-blox has implemented special features in LISA-U1 series modules to ease the design effort required for the
integration of a u-blox wireless module with a u blox GPS receiver.
Combining a LISA-U1 series wireless module with a u-blox GPS receiver allows designers to have full access to
the GPS receiver directly via the wireless module: it relays control messages to the GPS receiver via a dedicated
DDC (I
2
C) interface. A 2
nd
interface connected to the GPS receiver is not necessary: AT commands via the UART
serial interface of the wireless module allows a fully control of the GPS receiver from any host processor.
LISA-U1 series modules feature embedded GPS aiding that is a set of specific features developed by u-blox to
enhance GPS performance, decreasing Time To First Fix (TTFF), thus allowing to calculate the position in a shorter
time with higher accuracy.
