This is a HowTo, so it may be more appropriately placed somewhere else. Mods please feel free to move. I’m posting to help others.
This document describes the full process of configuring a SIMCOM SIM7600G/SIM7600X Rpi hat to connect to a remote cellular connection and provide IP traffic via a PPP adapter. This is a cheap, easy to use solution for bringing the Libre computers online in remote locations.
Tested on AML-S905X-CC, but should work on other models too.
Hardware:
AML-S805X-CC
Generic SIM7600X 4G Hat
2A USB Micro B power supply
Activated SIM card with data plan, and plan APN
Software:
Raspbian 11 (bullseye)
Kernel: 6.1.26-05272-g26c406245a2c #1 SMP PREEMPT_DYNAMIC Thu Apr 27 10:15:40 UTC 2023 aarch64 GNU/Linux
Setup
- Install SIM card into SIM7600X module (ensure to fully snap SIM carrier)
- Attach SIM7600X module to GPIO header
- From my tests, it is NOT NECESSARY to attach a USB cable to the SIM7600X module, as we will be using the buit-in UART for communications over the GPIO header, as well as providing power over the GPIO header.
Fully update Raspbian
sudo apt update -y
sudo apt upgrade -y
sudo reboot
Install necessary packages and tools
sudo apt -y install minicom ppp
Configure GPIO and UART
sudo raspi-config
Select 3: Interface Options, then I6 Serial Port. Select NO for Login Shell over Serial, then YES to enable serial.
Close and reboot.
Enable the uart-a profile on the GPIO header (you must do this every time you reboot, or add to /etc/local.rc file):
sudo ldto enable uart-a
Test modem
sudo minicom -b 115200 -D /dev/ttyAML6
Type the following commands to get responses from the SIM7600X modem:
at
OK
ati
... should show full details of SIM7600 module
OK
# Sim ready?
AT_CPIN?
+CPIN: READY
# Network available?
AT+COPS?
+COPS: 0,0,"D1"
# Network quality?
AT+CSQ
+CSQ: 4,0
Connect via PPP
Edit PPP config file:
sudo nano /etc/ppp/peers/rnet (You can replace ‘rnet’ with any filename, for example ‘tmobile’ if that is your carrier name)
Paste the following: Replace {APN} with your APN
#Set APN:
connect "/usr/sbin/chat -v -f /etc/chatscripts/gprs -T {APN}"
#Port:
/dev/ttyAML6
# Baudrate
115200
# Assumes that your IP address is allocated dynamically by the ISP.
noipdefault
# Try to get the name server addresses from the ISP.
usepeerdns
# Use this connection as the default route to the internet.
defaultroute
# Makes PPPD "dial again" when the connection is lost.
persist
# Do not ask the remote to authenticate.
noauth
# No hardware flow control on the serial link with GSM Modem
nocrtscts
# No modem control lines with GSM Modem
local
Edit the gprs file:
sudo nano /etc/chatscripts/gprs
It should already contain the following, but confirm:
# You can use this script unmodified to connect to cellular networks.
# The APN is specified in the peers file as the argument of the -T command
# line option of chat(8).
# For details about the AT commands involved please consult the relevant
# standard: 3GPP TS 27.007 - AT command set for User Equipment (UE).
# (http://www.3gpp.org/ftp/Specs/html-info/27007.htm)
ABORT BUSY
ABORT VOICE
ABORT "NO CARRIER"
ABORT "NO DIALTONE"
ABORT "NO DIAL TONE"
ABORT "NO ANSWER"
ABORT "DELAYED"
ABORT "ERROR"
# cease if the modem is not attached to the network yet
ABORT "+CGATT: 0"
"" AT
TIMEOUT 12
OK ATH
OK ATE1
# +CPIN provides the SIM card PIN
#OK "AT+CPIN=1234"
# +CFUN may allow to configure the handset to limit operations to
# GPRS/EDGE/UMTS/etc to save power, but the arguments are not standard
# except for 1 which means "full functionality".
#OK AT+CFUN=1
OK AT+CGDCONT=1,"IP","\T","",0,0
OK ATD*99#
TIMEOUT 22
CONNECT ""
Connect via PPP:
sudo pon [name of your /etc/ppp/peers/ file that you created above] If you changed the name from rnet, use the new name.
Run ifconfig to see if the PPP0 connection is up:
ifconfig
Test pinging an internet address using the ppp0 connection:
ping -I ppp0 8.8.8.8
(pings Google’s DNS)
You can shut down the connection with sudo poff [name of ppp file] (rnet is the default)
Automatically connect at boot
I will add more info here after testing.
References
Thanks to many documents, but mostly to SIM7600E: Setup via PPP | Andino
Also
GitHub - libre-computer-project/libretech-wiring-tool
Get Started with Super SIM, the Raspberry Pi 4 and the Waveshare 4G Hat | Twilio
RaspberryPi, SIM7600, GPSd - DEV Community
https://www.waveshare.net/w/upload/b/b2/SIM7600_Series_Open_Linux_Development_Guide_V2.00.pdf
TCP/IP testing with Simcom SIM7500 and SIM7600 Modules | M2MSupport.net