diff --git a/README.md b/README.md
index 74f6fa0..0d1028f 100644
--- a/README.md
+++ b/README.md
@@ -87,6 +87,91 @@ sysupgrade -v -n /tmp/openwrt-ipq40xx-generic-compex_wpj428-squashfs-sysupgrade.
 
 *Not written*
 
+## Using ModemManager
+
+Wait for modems:
+
+```
+mmcli -M
+```
+
+Connect/Disconnect:
+
+```
+mmcli -m 0 --simple-connect="apn=free"
+mmcli -m 0 --simple-disconnect
+```
+
+Set supported/preferred mode:
+
+```
+mmcli -m 0 --set-allowed-modes="3G|4G" --set-preferred-mode=4G
+mmcli -m 0 --set-allowed-modes="5G"
+```
+
+## Error
+
+Despite patching ModemManager simtech plugin, we get an error if we force 5GNR.
+We typed:
+
+```
+mmcli -m 0 --set-allowed-modes="5G"
+mmcli -m 0 --simple-disconnect
+mmcli -m 0 --simple-connect="apn=free"
+```
+
+We got:
+
+```
+Fri Mar 19 23:57:22 2021 daemon.warn [2633]: <warn>  [modem0] couldn't load operator code: Current operator MCC/MNC is still unknown
+Fri Mar 19 23:57:22 2021 daemon.warn [2633]: <warn>  [modem0] couldn't load operator name: Current operator description is still unknown
+Fri Mar 19 23:57:48 2021 daemon.info [2633]: <info>  [modem0] state changed (connected -> disconnecting)
+Fri Mar 19 23:57:48 2021 daemon.info [2633]: <info>  [modem0] state changed (disconnecting -> registered)
+Fri Mar 19 23:57:48 2021 daemon.info [2633]: <info>  [modem0/bearer1] connection #1 finished: duration 936s, tx: 79 bytes, rx :566 bytes
+Fri Mar 19 23:57:57 2021 daemon.info [2633]: <info>  [modem0] simple connect started...
+Fri Mar 19 23:57:57 2021 daemon.info [2633]: <info>  [modem0] simple connect state (4/8): wait to get fully enabled
+Fri Mar 19 23:57:57 2021 daemon.info [2633]: <info>  [modem0] simple connect state (5/8): register
+Fri Mar 19 23:57:57 2021 daemon.info [2633]: <info>  [modem0] simple connect state (6/8): bearer
+Fri Mar 19 23:57:57 2021 daemon.info [2633]: <info>  [modem0] simple connect state (7/8): connect
+Fri Mar 19 23:57:57 2021 daemon.info [2633]: <info>  [modem0] state changed (registered -> connecting)
+Fri Mar 19 23:57:57 2021 daemon.info [2633]: <info>  [modem0/bearer1] couldn't start network: QMI protocol error (14): 'CallFailed'
+Fri Mar 19 23:57:57 2021 daemon.info [2633]: <info>  [modem0/bearer1] call end reason (3): generic-no-service
+Fri Mar 19 23:57:57 2021 daemon.info [2633]: <info>  [modem0/bearer1] verbose call end reason (3,2001): [cm] no-service
+Fri Mar 19 23:57:57 2021 daemon.warn [2633]: <warn>  [modem0/bearer1] connection attempt #2 failed: QMI protocol error (14): 'CallFailed'
+Fri Mar 19 23:57:57 2021 daemon.info [2633]: <info>  [modem0] state changed (connecting -> registered)
+Fri Mar 19 23:57:57 2021 daemon.info [2633]: <info>  [modem0/bearer1] connection #2 finished: duration 0s, tx: 0 bytes, rx :0 bytes
+```
+
+And the new bearer contains:
+
+```
+root@OpenWrt:/# mmcli -b 1
+  ----------------------------
+  General    |           path: /org/freedesktop/ModemManager1/Bearer/1
+             |           type: default
+  ----------------------------
+  Status     |      connected: no
+             |      suspended: no
+             |     ip timeout: 20
+  ----------------------------
+  Properties |            apn: free
+             |        roaming: allowed
+  ----------------------------
+  Statistics |       attempts: 2
+             |       attempts: 1
+             | total-duration: 936
+             | total-bytes rx: 566
+             | total-bytes tx: 79
+```
+
+
+
+Next step: qmi-utils!
+
+ - https://forum.sierrawireless.com/t/mc7354-got-qmi-error-callfailed-when-starting-network/9053
+ - https://community.autopi.io/t/error-when-starting-qmi-connection/2338
+
+
 ## Logs
 
 uboot logs: