Connect the Raspberry Pi to the internet via GSM

Raspberry Pi	SIM800L
RX	TX
TX	RX
5v	4.3v (diode)
GND	GND

💥 DANGER
You must place a n4007 diode to supply the appropriate voltage for the module.

Install PPP

$ sudo apt-get update
$ sudo apt-get install ppp

First, we will create the PPP configuration file.

$ nano /etc/ppp/options

auth
crtscts
lock
hide-password
modem
mru 296
mtu 296
lcp-echo-interval 30
lcp-echo-failure 4
noipx
persist
asyncmap 0xa0000
mru 1500
refuse-chap
ipcp-max-failure 30
logfile /home/root/ppp

In this case we will use the PAP authentication file (they vary in relation to the provider).

$ nano /etc/ppp/pap-secrets

Modify this file according to your preferences.

*	hostname	""	*

guest   hostname        "*"     -
master  hostname        "*"     -
root    hostname        "*"     -
support hostname        "*"     -
stats   hostname        "*"     -

#	*	password
vivo	vivo	vivo

Now, you should now create the file inside the /etc/ppp/peer folder. Here will be the settings for each operator and the path to the chat file.

$ nano /etc/ppp/peers/tim-3g.provider

hide-password
noauth
debug
defaultroute
noipdefault
user vivo
remotename vivo
ipparam vivo
persist
usepeerdns
/dev/ttyAMA1 115200 crtscts
#replacedefaultroute -- Check it later
connect 'chat -v -f /etc/ppp/chat/tim-3g.chat'

Now we are going to create the file responsible for sending AT commands to the 3G module to establish the internet connection. In this case I'm using the SIM800L module.

ABORT 'BUSY'
ABORT 'NO CARRIER'
ABORT 'VOICE'
ABORT 'NO DIALTONE'
ABORT 'NO DIAL TONE'
ABORT 'NO ANSWER'
ABORT 'DELAYED'
TIMEOUT 20
REPORT CONNECT

"" AT
OK ATH
OK ATZ
OK ATQ0
OK AT+CGDCONT=1,"IP","zap.vivo.com.br"
OK ATDT*99#
CONNECT ''

In this case, I'm using TIM as an internet provider. So I'm going to put TIM's APN which is timbrasil.br.

After these steps it is recommended to restart the Raspberry.

Now it's finally time to test whether everything worked. To do this, simply execute the command below.

$ pon tim-3g.provider

To make sure it really worked, check if the PPP0 interface is online using the $ ifconfig.command and then ping -I ppp0 google.com.