So the problem really only seems to be the function
mbedtls_entropy_add_source
which takes in void*)&hrng as an argument, which is the hardware RNG, and which is not present on the STMF32F103
What is really strange though is, that when I look at the GCP2.0 code, there is a file iotc_bsp_tls_mbedtls.c which has a function iotc_bsp_tls_init, and which also calls all the functions for mbedtls initialization such as
mbedtls_platform_set_calloc_free
mbedtls_ssl_init
mbedtls_ssl_config_init
mbedtls_entropy_init
mbedtls_ctr_drbg_init
mbedtls_ctr_drbg_seed
but there is no call to mbedtls_entropy_add_source, so how does it do it's random number generation in this case.
This is a very complex bit of code, very difficult to follow...
The lack of documentation around how this SW is built, is very painful
