We’re trying to upgrade our devices to use the mc7455 modules (Rev A). Our devices are running opensuse linux with qmi_wwan drivers for the modems. For the last few years we’ve been using the mc7304 modems without issue. I have done tests on the mc7455 with the latest generic firmware and the Vodafone firmware but ran into issues with both.
When two mc7455 modules (using the Vodafone firmware) are connected and both have Vodafone SIMs, one of them gets 4G service while the other gets no service at all. I’m not sure what determines which SIM gets the 4G service, since it seems to change randomly after each reboot, but I haven’t tested this too much because it’s not something I could replicate on the generic firmware.
However I’ve now encounter another issue that occurs on both firmwares; after changing SIMs and rebooting the device, occasionally the mc7455 will connect but only get 3G service. So far I’ve managed to get it stuck on 3G with both Vodafone and EE SIMs. The temporary “fix” I’ve found is that if I run the
at!reset command it then reconnects with 4G service. Usually it doesn’t take me more than 2-3 reboots and SIM swaps for it to occur on Vodafone SIMs, sometimes even occuring on the first boot. I’m confident that this is not a signal issue, because I’ve replicated this in multiple areas with good 4G coverage. Power was another consideration, because the mc7455 modules do draw more than the mc7304 modules. However, this behaviour occurs when one mc7455 module is fitted, and our board is designed to support two. I have also tried using a generic third party modem holder, connected to a spare USB port on the motherboard, but again this gives the same results.
Vodafone SIM with 4G
at!gstatus? !GSTATUS: Current Time: 210 Temperature: 27 Reset Counter: 2 Mode: ONLINE System mode: LTE PS state: Attached LTE band: B20 LTE bw: 10 MHz LTE Rx chan: 6300 LTE Tx chan: 24300 LTE CA state: NOT ASSIGNED EMM state: Registered Normal Service RRC state: RRC Connected IMS reg state: No Srv PCC RxM RSSI: -50 RSRP (dBm): -81 PCC RxD RSSI: -98 RSRP (dBm): -139 Tx Power: 0 TAC: 6082 (24706) RSRQ (dB): -13.1 Cell ID: 000E0614 (919060) SINR (dB): 16.8 OK
at+csq +csq: 29,99 OK
at+cops? +cops: 0,0,"vodafone UK",7 OK
Vodafone SIM stuck with 3G (until modem reset)
at!gstatus? !GSTATUS: Current Time: 633 Temperature: 26 Reset Counter: 1 Mode: ONLINE System mode: WCDMA PS state: Attached WCDMA band: WCDMA 2100 WCDMA channel: 10687 GMM (PS) state:REGISTERED NORMAL SERVICE MM (CS) state: IDLE NORMAL SERVICE WCDMA L1 state:L1M_PCH_SLEEP LAC: 004A (74) RRC state: DISCONNECTED Cell ID: 02CC9281 (46961281) RxM RSSI C0: -53 RxD RSSI C0: --- RxM RSSI C1: --- RxD RSSI C1: --- OK
at+csq +csq: 30,99 OK
at+cops? +cops: 0,0,"vodafone UK",2 OK
Has anyone had similar issues? Or have any suggestions for things I can try?