mikkeli
169 lines
8.6 KiB
Markdown
169 lines
8.6 KiB
Markdown
---
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type: report
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date: 2026-10-07
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---
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# SIM7600G-H-M.2 (LTE + GNSS) Setup on Jetson Orin Nano
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## Result
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| Item | State |
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|------|-------|
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| LTE data via ModemManager + NetworkManager (QMI, `wwan0`) | Working: IPv4 + IPv6, ~9 Mbit/s DL observed |
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| Route priority: Ethernet (100) > WiFi (600) > LTE (1000) | Working |
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| GNSS engine + gpsd on `/dev/sim7600-gps` | **Working**: first 3D fix 2026-10-09 in the car (indoors: satellites seen, no fix) |
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## Hardware
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- **Board:** Jetson Orin Nano, hostname `mikkeli-orin-nano`, kernel `5.15.148-tegra` (L4T 36.4.4)
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- **Modem:** Waveshare SIM7600G-H-M.2 on the SIM7600G-H-M2 4G HAT, connected over USB
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- USB ID `1e0e:9001` (default composition, `AT+CUSBPIDSWITCH?` → `9001`)
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- Firmware `LE20B04SIM7600G-H-M2` / `SIM7600G_V2.0.2`
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- **SIM:** povo (KDDI/au MVNO), APN `povo.jp`, no user/password. Registers as `KDDI KDDI` (44051), LTE band 18.
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### USB interfaces (PID 9001)
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| Iface | Port | Driver | Role (as ModemManager sees it) |
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|-------|------|--------|-------------------------------|
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| 0 | ttyUSB0 | option | diagnostics (ignored) |
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| 1 | ttyUSB1 | option | **NMEA GPS** → `/dev/sim7600-gps` |
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| 2 | ttyUSB2 | option | AT (primary) |
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| 3 | ttyUSB3 | option | AT |
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| 4 | ttyUSB4 | option | audio |
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| 5 | `cdc-wdm0` + `wwan0` | **qmi_wwan** (self-built) | QMI control + network |
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## Problems hit and fixes
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### 1. `sim-missing`: SIM inserted after the modem powered up
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ModemManager reported `failed reason: sim-missing`, but `AT+CPIN?` returned `READY`. SIM hot-swap is off
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on this module (`AT+UIMHOTSWAPON: 0`), so a SIM seated after power-on isn't noticed until the modem re-initializes.
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Restarting ModemManager (or re-plugging the modem) fixes it.
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Hot-swap was deliberately left off. Turning it on needs the right `AT+UIMHOTSWAPLEVEL` for the HAT's SIM-detect
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wiring, and getting that wrong makes the modem report "no SIM" permanently. **Insert the SIM before powering the modem.**
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### 2. Tegra kernel has no `qmi_wwan` / `cdc-wdm`
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`CONFIG_USB_NET_QMI_WWAN` and `CONFIG_USB_WDM` are unset in the stock L4T kernel, so interface 5 had no driver,
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leaving PPP over a ttyUSB port as the only data path. Fixed by building both modules out of tree from
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upstream stable `v5.15.148` (see [rebuild](#rebuilding-qmi_wwan-after-a-kernel-update)).
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### 3. PPP dial causes `NW DETACH` on KDDI
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With PPP, every `ATD*99***<cid>#` ended about 32 s later with `NO CARRIER` + `+CGEV: NW DETACH`, `+CEER: No service available`.
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Two causes:
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- PDP context 1 (the LTE **initial-attach** APN) was preset to `au.au-net.ne.jp`, which a povo SIM can't use, and ModemManager put `povo.jp`
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on a new context 5. Fixed by setting context 1 to `povo.jp` (see below). After that the attach itself brings up a default bearer with an address.
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- Even with that fixed, a PPP dial on context 1 still triggered a network detach: PPP tries to activate a context that is already the
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active default bearer. **QMI does not have this problem**: it uses the existing default bearer. Do not use PPP with this SIM.
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Setting the attach APN (with ModemManager stopped; the setting persists in modem NVRAM):
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```
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AT+CFUN=4 # radio off, SIM stays powered (CFUN=0 powers the SIM down → CGDCONT returns ERROR)
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AT+CGDCONT=1,"IPV4V6","povo.jp"
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AT+CGDCONT=5 # remove stray contexts ModemManager had created
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AT+CFUN=1
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AT+CGPADDR=1 # should now show an IPv4 + IPv6 address
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```
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## Configuration applied
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### Kernel modules
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Source + Makefile live in `~/infra/qmi_wwan/` (per [GUIDELINES §1](../../GUIDELINES.md)):
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```
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~/infra/qmi_wwan/
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├── Makefile # obj-m += cdc-wdm.o qmi_wwan.o ; `make install` → /lib/modules/$(uname -r)/misc/ + depmod
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├── cdc-wdm.c # linux-stable v5.15.148 drivers/usb/class/cdc-wdm.c
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└── qmi_wwan.c # linux-stable v5.15.148 drivers/net/usb/qmi_wwan.c (has QMI_QUIRK_SET_DTR(0x1e0e, 0x9001, 5))
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```
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Installed to `/lib/modules/5.15.148-tegra/misc/{cdc-wdm,qmi_wwan}.ko`. They auto-load through the USB modalias after `depmod`,
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so no `/etc/modules` entry is needed.
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### NetworkManager connection `povo`
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```
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sudo nmcli con add type gsm ifname '*' con-name povo gsm.apn povo.jp \
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connection.autoconnect yes connection.autoconnect-retries 0 \
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ipv4.route-metric 1000 ipv6.route-metric 1000 ipv6.method auto
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```
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- `ifname '*'`: binds to whichever modem ModemManager exposes (now `cdc-wdm0`).
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- `connection.metered yes` (added 2026-10-08): marks LTE as metered so bulk transfers can refuse it. Project Yukart's
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map-tile sync uses this as its second guard (LAN-only rsync).
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- `autoconnect-retries 0` (forever): the default of 4 retries left the link permanently down after early failures. In a car, the modem may
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come up after NetworkManager.
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- Metric 1000 vs NM defaults Ethernet 100 / WiFi 600 → LTE only carries traffic when both are gone. Right after connecting the route
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can briefly show metric 21000 (NM's +20000 penalty until its connectivity check passes); it settles to 1000.
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Check:
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```
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mmcli -m any # state: connected, primary port: cdc-wdm0
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ip route show default # wlP1p1s0 metric 600, wwan0 metric 1000
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curl --interface wwan0 https://ifconfig.me
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```
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### Failover test (2026-10-08)
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Ran `/usr/local/sbin/lte-failover-test.sh` as a detached unit (`systemd-run --unit=lte-failover-test`). It turns the WiFi radio off for 180 s,
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samples every 10 s, then turns it back on, logging to `/var/log/lte-failover-test.log`. A `wifi-failsafe` timer (`systemd-run --on-active=10min nmcli radio wifi on`)
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was armed first, so a broken LTE path couldn't lock out a remote session.
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| Phase | Default route | Public IPv4 | Ping 1.1.1.1 | Tailscale → halogen |
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|-------|---------------|-------------|--------------|---------------------|
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| WiFi on | `wlP1p1s0` (600) | home ISP | ~12 ms | direct, LAN (3–4 ms) |
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| WiFi off | `wwan0` (1000), within 10 s | KDDI `106.128.x.x` | 25–55 ms | **direct over IPv6** to halogen's home IPv6 (40–85 ms), no DERP relay |
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| WiFi back | `wlP1p1s0`; IPv4 within 15 s, IPv6 within ~45 s (NM connectivity check) | home ISP | ~12 ms | direct, LAN |
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Zero failed samples (IPv4, DNS, Tailscale ping). An SSH session over Tailscale stayed up across both switches.
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Carrier CGNAT on IPv4 doesn't matter because povo gives a global IPv6 address, which Tailscale uses for a direct path.
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Note: `wwan0` also gets a kernel-installed IPv6 RA default route at metric 1024. That still ranks below WiFi (600) and only wins during the
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brief NM connectivity-check penalty (`+20000`) after WiFi returns.
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### GNSS
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- GNSS engine was already running (`AT+CGPS?` → `1,1`). Set to start on boot: `AT+CGPSAUTO=1` (persists in modem).
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- ModemManager location is **not** used. gpsd owns the NMEA port; ModemManager only labels it `(gps)` and leaves it unopened.
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- Stable device name, `/etc/udev/rules.d/99-sim7600-gps.rules`:
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```
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SUBSYSTEM=="tty", ATTRS{idVendor}=="1e0e", ATTRS{idProduct}=="9001", ENV{ID_USB_INTERFACE_NUM}=="01", SYMLINK+="sim7600-gps"
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```
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- `apt install gpsd gpsd-clients`, `/etc/default/gpsd`:
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```
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DEVICES="/dev/sim7600-gps"
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GPSD_OPTIONS="-n"
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USBAUTO="false" # hotplug would let gpsd probe the modem's AT ports and conflict with ModemManager
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```
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- `systemctl enable --now gpsd.socket gpsd`
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Check: `cgps` or `gpspipe -w -n 10`. On 2026-10-07, tested indoors, gpsd saw `nSat: 10, uSat: 0`, `mode: 1` (no fix).
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Next: test with the GNSS antenna (IPEX, labeled GNSS on the HAT) with a clear view of the sky. A cold start can take a few minutes.
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**2026-10-09, in the car:** first fix, `mode: 3` (3D) with 4 of 9 satellites used, GPS time valid. Passive GNSS antenna on the dashboard, facing the sky. No setup changes were needed;
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the indoor tests simply lacked sky view. If fixes prove slow or drop out while driving, try an active antenna (check the HAT supplies antenna bias first).
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## Rebuilding qmi_wwan after a kernel update
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Out-of-tree modules do not survive a kernel update. Signs: ModemManager shows `primary port: ttyUSB2` and there is no `/dev/cdc-wdm0`.
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```
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cd ~/infra/qmi_wwan
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# if the kernel's upstream base version changed, refresh the sources:
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# V=v5.15.xxx; for f in drivers/net/usb/qmi_wwan.c drivers/usb/class/cdc-wdm.c; do
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# curl -fL -o $(basename $f) "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/plain/$f?h=$V"; done
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make clean && make && sudo make install
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sudo modprobe qmi_wwan && sudo systemctl restart ModemManager
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```
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## Useful one-offs
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- Talk to the modem directly: `sudo systemctl stop ModemManager`, then use a terminal on `/dev/ttyUSB2`; start ModemManager again afterwards.
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(ModemManager holds ttyUSB2/3 while running.)
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- Verbose ModemManager log incl. AT traffic: `sudo mmcli -G debug` then `journalctl -u ModemManager -f` (resets on restart).
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