Abnormal slow bitrate (MTU=20). nRF52. SDK12.

[Oleg]

Good time dear Engineers!

Faced with a general Problem.

I use two nRF52 boards connection : Central <-> Peritheral. init data: MIN/MAX conn intervals = 10/30 ms

test Algorithm:

1. Write char value (19 bytes) use sd_ble_gattc_write(conn_h, &write_params);

2. Waiting for... BLE_EVT_TX_COMPLETE

3. Read char value use sd_ble_gattc_read(conn_h, char_h, 0);

4. Waiting for... BLE_GATTC_EVT_READ_RSP

Sometimes, the DELAY between 1& 2 or 3&4 reaches up to 2 seconds, but in other time all good & very fast (immediately). also, I noticed this happens periodically 'in waves'.

WHY? What parameters possible wrong ?

Thanks you!

CONN_PARAMETERS UPDATES DATA (20 ms):

LOG FILE:

[Petter Myhre]

What is your actual connection interval? Check them when you get connectected and whenever you get the BLE_GAP_EVT_CONN_PARAM_UPDATE event.

[Oleg]

hi dear Petter! I attached shot with my LOG data. both CONN_PARAM are veri fast - it's 20 ms. slave latency =1. I dont understand why so slow...

[Petter Myhre]

And after this you sometimes have up to two seconds between BLE_EVT_TX_COMPLETE and BLE_GATTC_EVT_READ_RSP? Strange. I'm not sure what could be causing this. Are you doing anything else? Could you share your complete project so I can test it here? What SDK and SoftDevice version are you using?

[Oleg]

I also attached the LOG terminal shot with full transactions. it shows delay between WR_REQ/RESP and READ_REQ/RESP.

[Petter Myhre]

Thanks. I'm not sure what is causing this. If you could edit your quesiton and upload your complete project that would be great. Or a project that exhibits the behavior. What SDK and SoftDevice version are you using? A sniffer trace would also be helpful, you can use the nRF Sniffer.