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CC2640: Data length extension and Android smart phones
it is very difficult to find out which smartphone supports DLE, for example I found out based on someone's experience that nexus 6 does not support DLE yet in thread you mentioned from above it looks like it does have a certain support for DLE.
any how I will try the nexus 6p , I will update this post if it worked.
in another question i am not seeing the ll_REQUEST_LEN in the sniff log created by the time ble sniffer. do you recommend using another sniffer?
Please see the update in the other thread regarding Google Pixel support of DLE: e2e.ti.com/.../542688
The DLE max values are typically not specified, so you must observe the values a particular device supports.
Regarding the sniffer, a standard BT4.0 LE sniffer can observe the LL_LENGTH_REQ and LL_LENGTH_RSP control packets opcodes, so I'm not sure what limitations you are observing with your current sniffer. Note that if the sniffer has not been updated it may not decode/parse this packet, but you can manually decode based on the data parameters.
cc2640 request LL_REQUEST_LEN : maxRxOctet of 251 & maxTxOctets of 251
Nexus P6 (or samsung note 5) LL_LENGTH_RSP: maxRxOctet of 251 & maxTxOctets of 27
I need to send more than 27 bytes in data packets from the cc2640 peripheral into the Android smartphone.
I based my tests on the throughput simple peripheral project.
I succeed to send 20 bytes notifications to the Android phone, the packets are also seen in sniffer.
when I increase the number of bytes to 30, the status = GATT_Notification( connectionHandle, ¬i, GATT_NO_AUTHENTICATION);
always return 0x1b; (and packet is not shown in the sniffer)
It also seems that I didn't get a ATT_MTU_UPDATED_EVENT callback after setDataLenCmd was sent (although that I saw the nexus P6 response in the sniffer log)
I also tried to read data through characteristic 5 ; when defining the array size less than 20 bytes I get the data ok into the nexus p6; however when the array size is 30 bytes I don't get it.
The negotiated DLE TX and RX sizes are independent of the ATT MTU size, thus they must be configured independently.
In Android, your client app must request a change in the ATT MTU size to use a value greater than the default 23. See this Stackoverflow article.
Also, you should not attempt to send more than the max ATT MTU size bytes (less based on the selected procedure). The examples in the SDK show how to request the max permissible size with the value is in the 'len' parameter.
