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i would appreciate if someone can explain one issue i'm experiencing with Raspberry Pi 3 model B acting as a Central device on a BLE connection with a Peripheral device, when updating connection parameters, and in particular with the connection event length.

After successfully connecting both devices and enabling notifications on the Central device using hcitool/gatttool commands i started receiving notifications on the Raspberry Pi3 model B, in particular, it receives 5 BLE packets with notified values per connection interval according to the default connection parameters. Once both devices are connected, i update the connection parameters in order to set, among other parameters, the CE length to 1 (0.625ms) using the following hcitool command (according to the answer i received from the thread Raspberry Pi3 BLE as Central device receiving just one packet per connection interval - gatttool/hcitool :

sudo hcitool cmd 0x08 0x13 0x40 0x00 0xFF 0 0xFF 0 0 0 0x60 0 0x01 0 0x01 0

Once the connection parameters are updated, i checked that the Raspberry Pi3 model B starts receiving just 1 BLE packet per connection interval, which is the expected behavioral. However, in case i update the connection parameters to set the CE length to 0 using the same procedure, the Raspberry Pi3 model B starts receiving 5 BLE packets with notified values per connection interval, which seems not to be coherent with the CE length value.

Could anyone give me an explanation of that issue?

Thanks

Mirada Veintitres
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1 Answers1

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The min / max ce length parameters are just a hint to the controller how much radio time it should dedicate to the connection.

I think Broadcom's implementation simply uses the value you provide as long as it works, if it is nonzero, and if it's zero it just picks space for 5 packets (or maybe some other value depending on the connection Interval).

Emil
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