More Networking with SIM7600G-H 4G HAT (B) for Raspberry Pi

I initially set up my Waveshare SIM7600G-H 4G HAT (B) for Raspberry Pi as described in the post last week.

Partly because the original web article I was following mentioned different modes of connecting to the internet, and partly because of my infatuation with IPv6, I decided to try to see the performance of different modes I might be able to set up with the device I have.

The support wiki for the device has four pages related to networking setup with the Raspberry Pi, RNDIS, NDIS, SIM868 PPP, and “3G Router“. I’d looked up definitions of NDIS and RNDIS on Wikipedia and didn’t really understand the differences, but the SIM868 page is titled “SIM7600X ECM dial-up Internet” and the ECM led me to believe it was the same as the second type of networking defined in the original article I’d been following. (Choosing QMI or ECM)

I’d been able to issue commands to the board by echoing the correct AT command to /dev/sttyUSB2. I was using the command echo AT+CGPS=1 >/dev/ttyUSB2 to enable the GPS on each boot. Following the Waveshare RNDIS instructions I blithely issued the command echo AT+CUSBPIDSWITCH=9011,1,1 >/dev/sttyUSB2 on my raspberry. The wwan0 device that I’d had set up and running went away and was replaced by a usb0 network device that Raspbian automatically enabled and acquired a valid internet address for. It had a routing metric that was lower than my wlan0 interface, but I figured it might be easier to organize this later without adding udhcpc into the mix of networking software on my raspberry. It also acquired an IPv6 address, which I’d not figured out how to do with the QMI setup and qmicli tools in my initial configuration. The original article mentioned possibly a lower networking latency using ECM vs QMI, so because one of the Waveshare pages had ECM in the title, I tried echo AT+CUSBPIDSWITCH=9018,1,1 /dev/sttyUSB2.

The latency seemed to be slightly different, and I wanted to switch back and do some real testing. That’s when I realized that I no longer had any /dev/ttyUSB devices to be able to send commands to. Completely power cycling the device made no difference. This is when I realized there are no reset jumpers on the device at all, and it had been able to remember the carrier APN that I’d initially set up before switching modes. Looking at the support web page, the only way I could figure out to recover the device was to connect it to a windows machine and install their drivers. I was not interested in downloading drivers from an unknown source and installing them on my primary workstation but realized my old Windows7 machine that hadn’t been turned on in close to a year was a good sacrifice if I could get things working.

First, I had to download the SIM7600X Driver, then I had to get their software.

Initial look at software

It took me a while to figure out that I had to hit the “Tools->STC/IAP15 ISP Programmer” menu, followed by the “Send Multi Char” tab on the resulting window pane to get the list of AT commands it could send.

Simcom Software

It also took me a while to recognize that while I could type commands into the primary window on the left, when I pasted commands that I’d typed in notepad, they were displayed but not executed by the card. The program also didn’t let me easily copy the contents of the main window so I could keep track of what commands I’d used and gotten as a result. After a while, I realized that this was essentially just a specialized serial terminal, and I had serial terminals I’m much more familiar with on my machine already. The Simcom HS-USB ports are visible in the windows device manager as COM12, COM13, COM14, and COM16. The purpose of each port is visible in the naming of the port in the current mode, NMEA, AT PORT, Diagnostics, and Audio.

AT+CRESET appeared to be a good command to get me back to a reasonable working state, but it only seemed to reboot the card, without changing any of the settings that had been stored. I was finally able to figure out that the AT&F command would set all the settings back to the factory defaults. After doing that I was no longer automatically connecting to Google FI, which at least meant I was no longer using up my data allowance while I was figuring things out.

I’d originally gotten into trouble by issuing the command AT+CUSBPIDSWITCH=9018,1,1. I came across the list of all available commands, which is much larger than what was listed in the Simcom Software itself. Issuing the command AT+CUSBPIDSWITCH? returns the current mode, and AT+CUSBPIDSWITCH=? lists the possible modes.

After the factory reset and switch back to 9011 mode, I got some of these results:

AT&F
OK
ATI
Manufacturer: SIMCOM INCORPORATED
Model: SIMCOM_SIM7600G-H
Revision: SIM7600M22_V2.0.1
SVN: 01
IMEI: 868822042540193
+GCAP: +CGSM

AT+CGDCONT?
+CGDCONT: 1,"IPV4V6","Telstra.internet","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 2,"IPV4V6","","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 3,"IPV4V6","","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 4,"IPV4V6","","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 5,"IPV4V6","","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 6,"IPV4V6","","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0

OK
AT+CGDCONT=?
+CGDCONT: (1-24),"IP",,,(0-2),(0-4),(0-1),(0-1)
+CGDCONT: (1-24),"PPP",,,(0-2),(0-4),(0-1),(0-1)
+CGDCONT: (1-24),"IPV6",,,(0-2),(0-4),(0-1),(0-1)
+CGDCONT: (1-24),"IPV4V6",,,(0-2),(0-4),(0-1),(0-1)

OK
AT+CUSBPIDSWITCH?
+CUSBPIDSWITCH: 9011

OK
AT+CUSBPIDSWITCH=?
+CUSBPIDSWITCH: (9000,9001,9002,9003,9004,9005,9006,9007,9011,9016,9018,9019,901A,901B,9020,9021,9022,9023,9024,9025,9026,9027,9028,9029,902A,902B),(0-1),(0-1)

Following some instructions I found on a post written by Mathieu Leguey, I was able to reconfigure the APN to connect to Google Fi. That page is also where I found the link to the complete list of commands. This other page is what led me to believe I need to set the APN twice to get IPv6 operating properly.

AT+CGDCONT?
+CGDCONT: 1,"IPV4V6","h2g2","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 2,"IPV4V6","","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 3,"IPV4V6","","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 4,"IPV4V6","","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 5,"IPV4V6","","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 6,"IPV4V6","h2g2","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0

I later realized I could configure the GPS to automatically start with the command AT+CGPSAUTO=1. The final configuration commands I decided to use that seem to work for my purposes are as follows:

AT&F
AT+CUSBPIDSWITCH=9011,1,1
AT+CGDCONT=1,"IPV4V6","h2g2"
AT+CGDCONT=6,"IPV4V6","h2g2"
AT+CGPSAUTO=1
SecureCRT Display

By doing this, I was able to avoid installing any networking drivers or configuration on Raspian that wasn’t automatically installed with the minimal system image. I should have been able to issue all of the commands via the echo command and the /dev/sttyUSB2 port if I’d not initially put the unit into 9018 mode and removed the USB control port.

ip a
ifconfig -a
route -v -n
wim@WimPiZeroW-Hope:~ $ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether b8:27:eb:7c:6a:80 brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.53/24 brd 192.168.0.255 scope global dynamic noprefixroute wlan0
       valid_lft 10481sec preferred_lft 9131sec
    inet6 2604:4080:1304:8010:347f:5b74:9cac:5a2/64 scope global dynamic mngtmpaddr noprefixroute
       valid_lft 27sec preferred_lft 17sec
    inet6 fe80::7a98:f2b1:147d:36d0/64 scope link
       valid_lft forever preferred_lft forever
3: usb0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000
    link/ether fe:5c:c9:12:f4:3a brd ff:ff:ff:ff:ff:ff
    inet 192.168.225.31/24 brd 192.168.225.255 scope global dynamic noprefixroute usb0
       valid_lft 42884sec preferred_lft 37484sec
    inet6 2607:fb90:8062:ac89:b44d:ec7e:82c0:b337/64 scope global mngtmpaddr noprefixroute
       valid_lft forever preferred_lft forever
    inet6 fe80::5ade:a00c:113f:dfcd/64 scope link
       valid_lft forever preferred_lft forever
wim@WimPiZeroW-Hope:~ $ ifconfig -a
lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 14  bytes 1876 (1.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 14  bytes 1876 (1.8 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

usb0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.225.31  netmask 255.255.255.0  broadcast 192.168.225.255
        inet6 2607:fb90:8062:ac89:b44d:ec7e:82c0:b337  prefixlen 64  scopeid 0x0<global>
        inet6 fe80::5ade:a00c:113f:dfcd  prefixlen 64  scopeid 0x20<link>
        ether fe:5c:c9:12:f4:3a  txqueuelen 1000  (Ethernet)
        RX packets 74  bytes 6149 (6.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 100  bytes 14461 (14.1 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.0.53  netmask 255.255.255.0  broadcast 192.168.0.255
        inet6 fe80::7a98:f2b1:147d:36d0  prefixlen 64  scopeid 0x20<link>
        inet6 2604:4080:1304:8010:347f:5b74:9cac:5a2  prefixlen 64  scopeid 0x0<global>
        ether b8:27:eb:7c:6a:80  txqueuelen 1000  (Ethernet)
        RX packets 3068  bytes 458727 (447.9 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 956  bytes 151187 (147.6 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wim@WimPiZeroW-Hope:~ $ route -v
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         mobileap.qualco 0.0.0.0         UG    203    0        0 usb0
default         192.168.0.1     0.0.0.0         UG    302    0        0 wlan0
192.168.0.0     0.0.0.0         255.255.255.0   U     302    0        0 wlan0
192.168.225.0   0.0.0.0         255.255.255.0   U     203    0        0 usb0
wim@WimPiZeroW-Hope:~ $ route -v -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.225.1   0.0.0.0         UG    203    0        0 usb0
0.0.0.0         192.168.0.1     0.0.0.0         UG    302    0        0 wlan0
192.168.0.0     0.0.0.0         255.255.255.0   U     302    0        0 wlan0
192.168.225.0   0.0.0.0         255.255.255.0   U     203    0        0 usb0
wim@WimPiZeroW-Hope:~ $ ping -I usb0 www.google.com -c 4
PING www.google.com(nuq04s43-in-x04.1e100.net (2607:f8b0:4005:810::2004)) from 2607:fb90:8062:ac89:b44d:ec7e:82c0:b337 usb0: 56 data bytes
64 bytes from nuq04s43-in-x04.1e100.net (2607:f8b0:4005:810::2004): icmp_seq=1 ttl=116 time=68.0 ms
64 bytes from nuq04s43-in-x04.1e100.net (2607:f8b0:4005:810::2004): icmp_seq=2 ttl=116 time=67.1 ms
64 bytes from nuq04s43-in-x04.1e100.net (2607:f8b0:4005:810::2004): icmp_seq=3 ttl=116 time=65.2 ms
64 bytes from nuq04s43-in-x04.1e100.net (2607:f8b0:4005:810::2004): icmp_seq=4 ttl=116 time=65.5 ms

--- www.google.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3005ms
rtt min/avg/max/mdev = 65.217/66.449/68.012/1.159 ms
wim@WimPiZeroW-Hope:~ $ ping -I wlan0 www.google.com -c 4
PING www.google.com(nuq04s43-in-x04.1e100.net (2607:f8b0:4005:810::2004)) from 2604:4080:1304:8010:347f:5b74:9cac:5a2 wlan0: 56 data bytes
64 bytes from nuq04s43-in-x04.1e100.net (2607:f8b0:4005:810::2004): icmp_seq=1 ttl=50 time=68.0 ms
64 bytes from nuq04s43-in-x04.1e100.net (2607:f8b0:4005:810::2004): icmp_seq=2 ttl=50 time=27.3 ms
64 bytes from nuq04s43-in-x04.1e100.net (2607:f8b0:4005:810::2004): icmp_seq=3 ttl=50 time=30.4 ms
64 bytes from nuq04s43-in-x04.1e100.net (2607:f8b0:4005:810::2004): icmp_seq=4 ttl=50 time=44.7 ms

--- www.google.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3008ms
rtt min/avg/max/mdev = 27.330/42.629/68.048/16.072 ms
wim@WimPiZeroW-Hope:~ $ lsusb
Bus 001 Device 003: ID 1e0e:9011 Qualcomm / Option SimTech, Incorporated
Bus 001 Device 002: ID 1a40:0101 Terminus Technology Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
wim@WimPiZeroW-Hope:~ $ lsusb -t
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
    |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/4p, 480M
        |__ Port 1: Dev 3, If 0, Class=Communications, Driver=rndis_host, 480M
        |__ Port 1: Dev 3, If 1, Class=CDC Data, Driver=rndis_host, 480M
        |__ Port 1: Dev 3, If 2, Class=Vendor Specific Class, Driver=option, 480M
        |__ Port 1: Dev 3, If 3, Class=Vendor Specific Class, Driver=option, 480M
        |__ Port 1: Dev 3, If 4, Class=Vendor Specific Class, Driver=option, 480M
        |__ Port 1: Dev 3, If 5, Class=Vendor Specific Class, Driver=option, 480M
        |__ Port 1: Dev 3, If 6, Class=Vendor Specific Class, Driver=option, 480M
ping results

One thing that jumped out when using the USB interface is that the default gateway is an internal Qualcomm name, mobileap.qualco.

lsusb results

I still need to figure out how to change the metric of usb0 to be higher than wlan0 probably installing the ifmetric program, following directions similar to this answer.

Update 7/17/2020

Adding an interface and metric line to the end of /etc/dhcpd.conf got me the routing I wanted without having to add any new programs. It also means the IPv6 stuff is taken care of automatically.

wim@WimPiZeroW-Hope:~ $ tail -5 /etc/dhcpcd.conf
#interface eth0
#fallback static_eth0

interface usb0
metric 400
wim@WimPiZeroW-Hope:~ $ route -n -v
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.0.1     0.0.0.0         UG    302    0        0 wlan0
0.0.0.0         192.168.225.1   0.0.0.0         UG    400    0        0 usb0
192.168.0.0     0.0.0.0         255.255.255.0   U     302    0        0 wlan0
192.168.225.0   0.0.0.0         255.255.255.0   U     400    0        0 usb0
wim@WimPiZeroW-Hope:~ $ route -n -v -6
Kernel IPv6 routing table
Destination                    Next Hop                   Flag Met Ref Use If
::1/128                        ::                         U    256 2     0 lo
2604:4080:1304:8010::/64       ::                         U    302 1     0 wlan0
2607:fb90:80c7:b02e::/64       ::                         U    400 2     0 usb0
fe80::/64                      ::                         U    256 1     0 usb0
fe80::/64                      ::                         U    256 1     0 wlan0
::/0                           fe80::b27f:b9ff:fe83:6591  UG   302 1     0 wlan0
::/0                           fe80::6c86:c4b4:1f1:c09    UG   400 2     0 usb0
::1/128                        ::                         Un   0   4     0 lo
2604:4080:1304:8010:347f:5b74:9cac:5a2/128 ::                         Un   0   2     0 wlan0
2607:fb90:80c7:b02e:b86b:f626:1fa9:3a62/128 ::                         Un   0   4     0 usb0
fe80::7a98:f2b1:147d:36d0/128  ::                         Un   0   3     0 wlan0
fe80::88be:29ff:2c84:e5a0/128  ::                         Un   0   5     0 usb0
ff00::/8                       ::                         U    256 2     0 usb0
ff00::/8                       ::                         U    256 2     0 wlan0
::/0                           ::                         !n   -1  1     0 lo
usb0 routing metric fixed

References: