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CCS/CC3220S-LAUNCHXL: HTTPS certificate format for "Let's Encrypt" Chain of Trust

Part Number: CC3220S-LAUNCHXL
Other Parts Discussed in Thread: CC3220S, UNIFLASH

Tool/software: Code Composer Studio

Hi, I'm using the CC3220S lanuch pad and i'm modifying the Httpget.c example to do a  HTTPS connection. i looked at almost every post we have on this so far. But  it doesn't matter what i do i get 


Connecting to : dd-wrt.

[NETAPP EVENT] IP Acquired: IP=172.25.1.16 , Gateway=172.25.0.1

Local time = Fri Jun 7 17:56:26 2019


Sending a HTTP POST request to 'valid-isrgrootx1.letsencrypt.org'

Error! code = -688, Description = httpTask: connect failed

I'm not sure how am i suppose to format my Https security parameter to work with https Mainly the rootCa part. 

httpClientSecParams.rootCa = "trustid-x3-root.pem";
httpClientSecParams.clientCert = NULL;
httpClientSecParams.privateKey = NULL;

here is the website that of the chain of trust that i'm using. 

https://letsencrypt.org/certificates/

Thanks in advance for any advice !!!