I think the 'len' type of the coap_option_t structure should be uint16_t.

[neo1seok]

Hi!!
Your source is simple and tidy, I'm checking to apply. But I have a part to comment.

If the delta value in the options section of coap is 13 or 14, the option type may be greater than 255. However, the 'len' type of the structure 'coap_option_t' is set to 'uint8_t', so it should be applied to uint16_t.

I think this type doesn't exceed 1 byte. Onem2m is defined with more than 256 values ​​in iot platform. If you define it as 2 bytes, I think it can be extended.

thank you.