waitResponse() check ambiguity

[sslupsky]

I think I have found an situation where there is ambiguity in waitResponse(). This method is used to parse the AT response from the modem. It defaults to parse for r1=LORA_OK ("+OK") or r2=LORA_ERROR ("+ERR"). There appears to be provision to add additional checks (r3, r4, r5).

The following line is typical of the parsing method used:

MKRWAN/src/MKRWAN.h

Line 855 in 2fa519d

if (r1 && data.endsWith(r1)) {

A problem arises because the modem can return seven types of error message as shown here:

https://github.com/arduino/mkrwan1300-fw/blob/63787fe5ed8bd07119caba20d2065a26004b2261/Projects/Multi/Applications/LoRa/AT_Slave/src/command.c#L83-L93

Because the parsing method uses the .endswith() string method, and the string is checked with every new character, any error message will match the first "+ERR" and therefore, you cannot add additional error codes when you call waitResponse().

I think this needs to be fixed. It seems to me that the string comparison should be done only after the entire response is received from the modem?

[flhofer]

Good point. Maybe parse once a \r, +, " " or = is received. Actually, the same way the firmware is doing it. However, at the moment I don't think there is anything else evaluated but the mere ERR or OK ( == or != 1 is tested), so it wouldn't make that big of a change anyway.

[flhofer]

Should be done with #93 if pulled :)