I am developping an application on the STM32 SPBTLE-1S module (BLE 4.2). The module connects to a Raspberry Pi.
When the connection quality is low, a disconnection will sometimes occur with error code 0x28 (Reason: Instant Passed) before the connection timeout is reached.
Current connection settings are:
Conn_Interval_Min: 10
Conn_Interval_Max: 20
Slave_latency: 5
Timeout_Multiplier: 3200
Reading more on this type of error, it seems to happen when "an LMP PDU or LL PDU that includes an instant cannot be performed because the instant when this would have occurred has passed." These paquets are typically used for frequency hopping or for connection updates. In my case, they must be frequency hoping paquets.
Any idea on how to prevent these disconnections caused by "Instant Passed" errors? Or are they simply a consequence of the BLE technology?
Your question sounds similar to this one
In a nutshell, there's only two possible link layer requests that can result in this type of disconnect (referred to as LL_CONNECTION_UPDATE_IND & LL_CHANNEL_MAP_IND in the latest v5.2 Bluetooth Core Spec)
If you have access to the low level firmware for the bluetooth stack on the embedded device, what I've done in the past is increase the number of slots in the future the switch "Instant" is at so there's more time for the packet to go through in a noisy environment.
Otherwise the best you can do is try to limit the amount of times you change connection parameters to make that style of disconnect less likely to occur. (The disconnect could still be triggered by channel map change but I haven't seen many BLE stacks expose a lot of configuration over when those take place.)