Hey,

I started a driver for the sim7020 NBIoT modem using at-commands. Super helpful!
Unfortunately, the handling of optional parameters seems to be different in this chip. Instead of providing empty comma separated parameters the chip seems to also make the delimiting comma optional.
e.g. creating a http session (section 8.2.1 in the AT reference pdf:

        at_commands::builder::CommandBuilder::create_set(buffer, true)
            .named("+CHTTPCREATE")
            .with_string_parameter("http://blabla")
            .with_optional_string_parameter(None)
            .with_optional_string_parameter(None)
            .finish()

// should produce: AT+CHTTPCREATE=http://blabla,,

The chip will return an error. Same happened with all other commands on that IC using optional parameters. If, instead, I use:

        at_commands::builder::CommandBuilder::create_set(buffer, true)
            .named("+CHTTPCREATE")
            .with_string_parameter("http://blabla")
            .finish()

// should produce: AT+CHTTPCREATE=http://blabla

it works fine.

Is this a different flavor of AT commands in general? If not, maybe a feature flag e.g. add_comma_on_optional_commands or alike to switch the delimiters on/off?
Looking forward hearing your thoughts on that.
Cheers

Marius