Provisioning the MMI 3G+ with LTE Mobile Data Post 3G Shutdown

[DrGER]

After collecting all the pieces, I "installed" LTE data to our MMI 3G+ system this afternoon using our old legacy Freedompop SIM, a Digi LTE router, USB ethernet adapter, and bespoke MMI/USB cable. The idea was to locate the Digi LTE router under the MMI main unit and behind the climate controls, and use the existing GSM antenna cable with a short FAKRA/SMA adapter cable.

The trickiest part of the installation was getting a direct USB connection from the back of the MMI main unit rather than from the AMI connector in the glovebox. Sourcing the components to make a proper MMI/USB cable took some effort, but better late than never. Components included an old (working) after-market AMI USB cable, a yellow FAKRA HSD connector with pigtail cable 4F1035750C, green T12 connector block 8X0035447A, 3 repair wire ends, and the "detect" resistor from the non-OE AMI USB cable:


MMI/USB cable connections:

T4ap/1 (USB D+)----[USB/3]
T4ap/2 (not used) 
T4ap/3 (USB D-)----[USB/2]
T4ap/4 (GND)---------------+ 
T12y/3 (USB +5V)---[USB/1] |  
T12y/4 (USB GND)---[USB/4] |  
T12y/6 (Detect)---1K ohm---+

The finished MMI/USB cable:


I modified the stock installFairMode.sh as an SD script to include installation of a proper resolv.conf file:

#!/bin/ksh
# 20220320 drger; DLink USB Ethernet adapter settings
# Script startup env from copie_scr.sh
showScreen ${SDLIB}/scriptStart.png
touch ${sdpath}/.started
xlogfile=${SDPATH}/run-$(getTime).log
exec > ${xlogfile} 2>&1
echo "[INFO] Start: `date`; Timestamp: $(getTime); Train: $SWTRAIN"

SOURCE=/mnt/efs-system/scripts/Connectivity

echo "[ACTI] Copying data for LAN."
mount -uw /mnt/efs-system
mount -uw /mnt/efs-persist

# Backup GSM related files:
if [ -f /etc/browser/common.cfg ]
then
   echo "[ACTI] Saving /etc/browser/common.cfg"
   cp -v /etc/browser/common.cfg ${SDVAR}/etc-browser-common.cfg.GSM
   cp -v /etc/browser/common.cfg /etc/browser/common.cfg.GSM
fi

if [ -f /lsd/poiproducer.properties ]
then
   echo "[ACTI] Saving /lsd/poiproducer.properties"
   cp -v /lsd/poiproducer.properties ${SDVAR}/lsd-poiproducer.properties.GSM
   cp -v /lsd/poiproducer.properties /lsd/poiproducer.properties.GSM
fi

if [ -f /lsd/MMI3G_MyAudi.properties ]
then
   echo "[ACTI] Saving /lsd/MMI3G_MyAudi.properties"
   cp -v /lsd/MMI3G_MyAudi.properties ${SDVAR}/lsd-MMI3G_MyAudi.properties.GSM
   mv -v /lsd/MMI3G_MyAudi.properties /lsd/MMI3G_MyAudi.properties.GSM
fi

if [ -f /etc/ppp/pf.conf ]
then
   echo "[ACTI] Saving /etc/ppp/pf.conf"
   cp -v /etc/ppp/pf.conf ${SDVAR}/etc-ppp-pf.conf.GSM
   cp -v /etc/ppp/pf.conf /etc/ppp/pf.conf.GSM
fi

echo "[INFO] LAN setup..."
echo "[ACTI] Install resolv.conf.LAN"
cp -v ${SDVAR}/resolv.conf.LAN /mnt/efs-system/scripts/Connectivity/
cp -v ${SDVAR}/resolv.conf.LAN /mnt/efs-system/etc/resolv.conf

echo "[ACTI] Patch MyAudi."
cp -v ${SOURCE}/myaudiconnect_nodataconnect.jar /lsd/myaudiconnect_nodataconnect.jar
#rm -v /lsd/MMI3G_MyAudi.properties

echo "[ACTI] Create usedhcp flag."
touch /HBpersistence/usedhcp

echo "[ACTI] Create DLinkReplacesPPP flag."
touch /HBpersistence/DLinkReplacesPPP

echo "[ACTI] Copy common.cfg."
cp -v ${SOURCE}/common.cfg /etc/browser/common.cfg

echo "[ACTI] Copy poiproducer.properties"
cp -v ${SOURCE}/poiproducer.properties /lsd/poiproducer.properties

echo "[ACTI] Copy pf.conf"
cp -v ${SOURCE}/pf.conf /etc/ppp/pf.conf

# Script cleanup:
echo "[INFO] End: `date`; Timestamp: $(getTime)"
showScreen ${SDLIB}/scriptDone.png
rm -f ${sdpath}/.started
exit 0

After running the script, the MMI system will look for a DLink (or equivalent chipset) USB ethernet adapter as its network interface.

Putting the hardware together, we get:


Notice the green status indicator on the map display, indicating that the Google Earth client is connected and authenticated to the back-end service.

And the GEM offers confirmation, first that the MMI system recognizes the USB ethernet adapter:


and that the ethernet device gets an IP address from the Digi LTE router DHCP server:


Power to the Digi LTE router comes from a Term 75 switched circuit on Fuse Panel C/1, so it's only on with the ignition; the DHCP server is ready before the MMI system tries to get an IP address, so that should be sufficient in normal operation. We'll see how this works out in the coming summer travel months. --g