Dear @dpgeorge ,
I am trying to establish SSL connection to AWS IoT via ESP32. Normally i have below three files (certs and key) in flash folder.
KEY_PATH = "/flash/cert/deviceCert.key"
CERT_PATH = "/flash/cert/deviceCertAndCACert.pem"
CACERT_PATH = "/flash/cert/root.pem"

In first, i defined the ssl_params={"certfile":CERT_PATH, "keyfile":KEY_PATH, "ca_certs":CACERT_PATH}) as like that but i was always getting "Error in mqtt connect: [Exception] TypeError: extra keyword arguments given." error.

Then, i have checked the modussl_mbedtls.c in extmod and SSL parameters are defined as like in struct below (Line 59).

struct ssl_args {
    mp_arg_val_t key;
    mp_arg_val_t cert;
    mp_arg_val_t server_side;
    mp_arg_val_t server_hostname;
};

i have adjusted the ssl_params={"cert":CERT_PATH, "key":KEY_PATH})
I have tried to create connection without using cacert.

Then, it started to try establishing connection but i have received following error then board reboots.

assertion "ret == 0" failed: file "../../extmod/modussl_mbedtls.c", line 182, function: socket_new
abort() was called at PC 0x40135e2f on core 0

Backtrace: 0x4008c983:0x3ffb61f0 0x4008c9af:0x3ffb6210

Rebooting...
0�?anic'ed ( 0�?anic'ed ( 0�?anic'ed ( 0�?anic'ed ( 0�?anic'ed ( 0�?anic'ed ( 0�?anic'ed (ets Jun  8 2016 00:22:57

rst:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)

I will be glad if it is possible to add "cacert" parameter inside arguments of ussl module.

Thanks for your efforts...