How? by not buying a Huawei EC121, of course!
Seriously Huawei. Your firmware engineers need a huge punch in the face. And then some re-education. With firmware version 11.100.17.00.114 at least, there are two complete stupidities that deserve a huge public mocking.
First, the response to AT+GCAP is simply “+CIS707-A, +MS, +ES, +DS, +FCLASS”. No, it’s not prefixed with “+GCAP: ” like every other modem on the planet that I’m pretty sure the relevant standards (TIA/EIA/IS-131, TIA/EIA-602, and V.250) require:Extended syntax result codes shall be prefixed by the “+” character to avoid duplication of basic format result codes specified in TIA-602 and by manufacturers. Following the “+” character, the name of the result code appears; result code names shall follow the same rules as command names (see 5.4.1).
The EC121 engineers apparently decided they couldn’t even follow their own documented responses for the CM300/CM320/CM350 for example. I’m assuming they don’t rewrite the firmware every time they make a new part, but I never underestimate the capacity for stupidity.
Second, when it encounters a command it doesn’t like, it sometimes returns “COMMAND NOT SUPPORT”. Seriously. Not “ERROR” or “ERR” like every other modem on the planet. Maybe they were so high on crack they forgot the “ED” too.
Seriously, what the fuck? Stop it. No really, stop being dumb.