SLM HTTP client hangs with large payload

[Anthony Ambuehl]

I recently switched  from 1.5.1 to 1.6.1 and I'm now finding the SLM is misbehaving.

When I try to send a large payload such as 933 bytes of data, I find the CTS signal goes low after 274 bytes of data were sent.  (There is some buffering in my mcu so probably less received at SLM uart) 

It seems like the SLM data mode uses a ring buffer that is only 256 lines and the datamode cannot handle payloads longer than this.  

Please confirm large payloads work in 1.6.1.  

Also any advice on how to get debug logging from SLM_AT_HOST and SLM_AT_HTTPC ?  I'm running from SES with stock SLM example...

[Håkon Alseth]

Hi,

 

I find the CTS signal goes low after 274 bytes of data were sent.  (There is some buffering in my mcu so probably less received at SLM uart) 

Just to clarify, from which side is it set low?

 

Also any advice on how to get debug logging from SLM_AT_HOST and SLM_AT_HTTPC ?  I'm running from SES with stock SLM example...

If you set the log level to debug (4) here:

https://github.com/nrfconnect/sdk-nrf/blob/v1.6.1/applications/serial_lte_modem/prj.conf#L8

 

Then it should print out debug logs over RTT. Could you try this and attach the log showing the issue?

 

Kind regards,

Håkon

[Anthony Ambuehl]

CTS at my external MCU is driven by the nrf9160 SLM.  The signal indicates the external mcu should stop sending data.

Regarding the debug logs... (my apologies for basic questions, I'm new to NCS and there are a lot of docs to search through)

1) After changing prj.conf do I need to run cmake from Project..Run cmake.. ?

2) Is it correct for me to put this in the prj.conf:

CONIG_SLM_LOG_LEVEL=4

3) What does CONFIG_SLM_LOG_LEVEL_INF=y  do?

[Anthony Ambuehl]

oh, just realized the link you posted highlighted a specific line to change, thanks for that!

[Anthony Ambuehl]

I tried enabling logs by changing prj.cnf line 8 to:

CONFIG_LOG_DEFAULT_LEVEL=4

I ran cmake and the rebuilt merged.hex (F7)

The only log lines are produced by the bootloader and then it goes silent. 

Is it possible that logging is disabled completely somehow or that the application has a different location for the RTT block vs the bootloader? 

Perhaps there are 2 RTT blocks one in secure  zone and one non-secure?

Is there a way to build and run where I will get debug logs for the application?  

[Anthony Ambuehl]

I worked on it some more this morning and identified an issue in my code, that is caused by an unusual behavior from the SLM.  

While in datamode receiving the payload data, the SLM will periodically send the OK_STR ("OK").  My code was not expecting the OK to be sent until after the data was fully transferred so it proceeded into a state where waiting for the XHTTPCRSP message.  

Is it expected for the OK message to be resent every 27 milliseconds when in datamode?. Is this some sort of progress indication?

It seems after starting an HTTPCREQ, the OK message should be ignored until the HTTPCRSP is received.  I suspect there is also some case where HTTPCREQ return values other than 0 and 1, which is not documented. 

a*