SDK 12.3.0 - connection parameter config got fatal error

[carlche]

Hi there,

Based on apple recommendation, I've chosen the next connection parameter set (and tested the parameter set works on other platform such as TI and Dialogue chip):

140 #define MIN_CONN_INTERVAL MSEC_TO_UNITS(1979, UNIT_1_25_MS) /**< Minimum acceptable connection interval (1.979 seconds). */

141 #define MAX_CONN_INTERVAL MSEC_TO_UNITS(1999, UNIT_1_25_MS) /**< Maximum acceptable connection interval (1.999 second). */

142 #define SLAVE_LATENCY 0 /**< Slave latency. */

143 #define CONN_SUP_TIMEOUT MSEC_TO_UNITS(2000, UNIT_10_MS) /**< Connection supervisory timeout (2 seconds). */

However the RTT log (ble_app_proximity) in this case says "APP ERROR:ERROR:Fatal" and fail to boot up.

When change it back to the Nodic default config, the chip boots OK.

Can you please give it a quick try and figure out what's going on behind the scene? Why it fails to boot up using a legitimate set of connection parameters?

Thanks for your attention, Carl

[Sigurd]

Hi,

From the Bluetooth specification we have the following requirement:

The connSupervisionTimeout shall be a multiple of 10 ms in the range of 100 ms to 32.0 s and it shall be larger than (1 + connSlaveLatency) * connInterval * 2.

In your case, you have connSupervisionTimeout set to 2000ms, and connInterval_max set to 1999 ms. I.e. connSupervisionTimeout > connInterval_max *2 requirement is not fulfilled.

When setting the connection parameters with sd_ble_gap_ppcp_set(), it will return NRF_ERROR_INVALID_PARAM. You will then enter the error-handler, and get the Fatal message

You therefore need to set the CONN_SUP_TIMEOUT to 4000ms with the connection interval you have chosen. This is also in line with the Apple Bluetooth Design Guidelines, where you have

2 seconds ≤ connSupervisionTimeout ≤ 6 seconds

[carlche]

My bad, yes it was set to connSupervisionTimeout = 6s for the other platforms. Changed to 6s and it work on nrf51 DK. Sorry for the fuss.