Bluetooth connection parameters

[jon]

I am working with nRFx modules and have a few questions about updating parameters. I started my project with an example and modified what I needed. However, I am not sure if the parameters are getting set when I change them. Currently I go into main.c and change the following parameters:

#define MIN_CONN_INTERVAL                          MSEC_TO_UNITS(20, UNIT_1_25_MS)           
#define MAX_CONN_INTERVAL                         MSEC_TO_UNITS(75, UNIT_1_25_MS)           
#define SLAVE_LATENCY                                  0                                         
#define CONN_SUP_TIMEOUT               
#define FIRST_CONN_PARAMS_UPDATE_DELAY  APP_TIMER_TICKS(5000, APP_TIMER_PRESCALER)  
#define NEXT_CONN_PARAMS_UPDATE_DELAY   APP_TIMER_TICKS(30000, APP_TIMER_PRESCALER) 
#define MAX_CONN_PARAMS_UPDATE_COUNT    3                                
#define TX_POWER_LEVEL                                4      

If I change these parameters, specifically the first three (connection interval, slave latency, and connection supervision timeout), will they automatically be set on with the central? I am currently connecting to a windows 10 device and trying to figure out if the parameters are being updated and if not, why? How would I check to see if they are getting updated?

[endnode]

What project you use? There are like hundred main.c files in SDK;) Normally these constants are indeed used in the code when you recompile and load it to the board so they should be used. The question is what you expect to happen;) Normally there is no debugging on Link Layer on systems like smart phones or Windows boxes so the usual way is to get RF analyzer/sniffer and see what is happening in the air.

[endnode]

Finally I would say that still the truth lives only in the radio so using BLE sniffer or some more expensive radio analyzer would tell you exactly what are connection parameters at the beginning and how different Masters (GAP Central devices) react on simple read of PPCP values from GATT Server or explicit Peripheral Connection Parameters Change procedure. Don't be surprised that if you target mobile phones and similar devices you can see very different behavior starting from proper rejecting to accepting but with several seconds of delay or accepting but not acting accordingly or simply ignoring... so in the end it's quite difficult to fine-tune the application logic to really improve your situation. And basically impossible if you want to have 100% compatibility with all possible centrals. If you target one or few specific devices then it's probably good way.