And thank you very much for your very quick answer.
I am sorry I haven't repsonded before, but we had a national Holiday in Denmark Friday the 8th.
I will try to answer on your comments.
Regarding the buffer counts, having a value of 14 is written in the documentation of zephyr 2.2.0 as the link below shows.
Regarding the buffer counts, having a value of 36 is written in the documentation of zephyr 2.2.0 as the link below shows.
We are already using a maximum heap size for CONFIG_MBEDTLS_HEAP_SIZE of 65356.
CONFIG_MBEDTLS_SSL_MAX_CONTENT_LEN is set to 8196.
And it is the same configuration in both Ethernet and GSM modem.
Using the maximum value of 16384 for CONFIG_MBEDTLS_SSL_MAX_CONTENT_LEN gives another error of "<err> net_sock_tls: TLS handshake error: -4310" when running state MBEDTLS_SSL_CERTIFICATE_VERIFY.
Anyway, this is the "maximum" configuration we use now, where some buffers and also some NET RX and TX stacks are increased to the double of default.
I have disabled some shell to get more memory available for this.
And I am still stuck with the same error in the GSM modem variant.
The Ethernet variant still works perfect.
Again, I have attached the two auto generated header files, so they can be compared directly.
Basically the header file for Ethernet has some ETH related configuration and the GSM modem header has some MODEM and PPP related configuration.
I have also attached the two proj.cnf so they can be compared directly.
And basically you will see, that there is a section at the bottom for using GSM modem, which is based on the GSM_modem sample project.
And when building for Ethernet, you will see this section outcommented more or less, except for the buffers and some net stacks. The only other thing Ethernet variant has enabled is the DHCPV4.
Regarding using latest upstream zephyr version I have tried using 2.2.3rc1 and compare with 2.2.0.
I am only testing the gsm_modem sample project, but using UART 3 on the frdm_k64f board, which is compatible with Arduino pinout, which my modem shield uses.
Using an oscilloscope, no data is sent out on UART 3 for communicating with the modem shield, when I test with zephyr 2.2.3rc1.
Everything works fine with zephyr version 2.2.0 and I can use the net shell to ping some IP addresses, meaning the modem is being configured correct via PPP over UART 3.
What am I missing in order to sent out data on UART 3 on the frdm_k64f board??
There are some changes to the configuration of UART 3 between zephyr 2.2.3rc1 and 2.2.0.
In zephyr 2.2.0 the following configuration parameters are needed to make the UART 3 work, which can be seen in the attahced proj.2.2.0.conf for the gms_modem sample project:
CONFIG_SERIAL=y CONFIG_UART_MCUX_3=y CONFIG_MODEM_GSM_UART_NAME="UART_3"
In zephyr 2.2.3rc1 it seems like CONFIG_UART_MCUX_3=y is no longer needed and I only have to set the two other configuration parameters, which can be seen in the attached proj.2.2.3rc1.conf for the gms_modem sample project: CONFIG_SERIAL=y CONFIG_MODEM_GSM_UART_NAME="UART_3"
I hope to get 2.2.3rc1 up and running to see if it solves my issues with mbedtls certificate handshaking, as you also suggest as first thing to try.