I have some problems with mbedTLS during ECDSA signing process.

I followed the example supplied with the source code and write this code:

mbedtls_pk_init(&pk);
mbedtls_pk_parse_key(&pk, (const unsigned char *) flash.flash_ver0.ecc_priv_key, strlen(flash.flash_ver0.ecc_priv_key) + 1, (const unsigned char *)CA_DEF_ISSUER_PWD, CA_DEF_ISSUER_PWD_LEN);
mbedtls_md(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256), msg, msg_len, hash);
mbedtls_pk_sign(&pk, MBEDTLS_MD_SHA256, hash, 0, tmp, (size_t *)&len, mbedtls_ctr_drbg_random, &ctr_drbg);

The private key is an ECC key with 384 bit. I have two issue:

1) In tmp variable I found the signature, but it is 72 byte, instead of 96 (384*2/87);

2) On this signature I try to make a verify, but fails.

Where I'm wrong?

Best regards,