Basic Bluetooth Communication

RE: Basic Bluetooth Communication

ovrebekk — Fri, 12 Nov 2021 12:29:42 GMT

[quote user="it0406"]

ovrebekk said:
Not sure what you mean about the information being 'right'?

I mean the return value like NRF_SUCCESS or other faults, whether APP got a correct information from SD.

[/quote]

On the scanner side you won't get any event unless the advertise packet was successfully received. In other words, the scan event is only triggered for correctly received advertise packets.

[quote user="it0406"]As I understand, SD sends advertisement packets to APP and APP checks itself with CRC. If CRC fails, the packet won't be used. Then SD doesn't need reply or answer from APP. Am I right? [/quote]

The CRC check is handled directly by the Bluetooth link layer in the SoftDevice, and does not involve the app at all. If the CRC check fails the packet will be ignored by the SoftDevice, and the app will not get any information about it from the SoftDevice.

An important thing to understand about advertise packets is that there is always a lot of lost packets, since the advertiser and scanner is not synchronized. When sending advertise packets you should always assume that only a fraction of the packets you send are received by any one scanner.

Best regards
Torbjørn

RE: Basic Bluetooth Communication

it0406 — Thu, 11 Nov 2021 23:10:06 GMT

[quote userid="2116" url="~/f/nordic-q-a/81526/basic-bluetooth-communication/338187#338187"]Not sure what you mean about the information being 'right'?[/quote]

I mean the return value like NRF_SUCCESS or other faults, whether APP got a correct information from SD.

[quote userid="2116" url="~/f/nordic-q-a/81526/basic-bluetooth-communication/338187#338187"]All BLE packets include a 24-bit CRC code at the end to detect bit errors, and if the CRC check fails the packet will be ignored. [/quote]

As I understand, SD sends advertisement packets to APP and APP checks itself with CRC. If CRC fails, the packet won't be used. Then SD doesn't need reply or answer from APP. Am I right?

Best regards

it0406

RE: Basic Bluetooth Communication

ovrebekk — Tue, 09 Nov 2021 13:38:36 GMT

[quote user=""]As my logic, SD should also send a message to the advertiser like whether SD got the advertisement well or not.[/quote]

There is no acknowledge of advertise packets. Advertise packets are inherently asynchronous, and can be sent to any number of scanners at the same time, so it doesn't make sense to acknowledge them.

The only thing a scanner is allowed to send to an advertiser is a scan request or a connection request.

[quote user=""]OR APP and SD should communicate after advertising whether the infomation is right or the scanning is failed.[/quote]

Not sure what you mean about the information being 'right'?

All BLE packets include a 24-bit CRC code at the end to detect bit errors, and if the CRC check fails the packet will be ignored.

Best regards
Torbjørn